Bio 332
-If disturbed, pops recover to stable equilibrium point (dampening oscillations) -Equilibrium stabilized by density-dependent pop growth of prey (as a function of K) -Clockwise rotation of prey isocline increases stability -Predators can drop to very low values in some cycles: stochastic fluctuations could drive system to extinction
"Greater ecological realism of LV prey model"
-Competition most intense in resource rich environments -strong competitors = grow rapidly, fills soil volume with roots (strong in any kind of environment) -strong competitor for light, also strong for nutrients -stressed (resource poor env): soil and canopy are not filled, competition should be less important
"Grimes Trait Triangle (plants)"
see written notes
"LV models with both intra and inter comp"
-Unstable equilibrium point -Predator and prey move away from equilibrium in growing oscillations -No convergence with growing oscillations
"Phase-plane analysis assuming type 2 fxn response, no density dependence"
Stable equilibrium: V*1 and P*1 -predator needs high prey density to survive -intraspecific prey competition is strong -Predator and prey will converge to equilibrium with no cycles Unstable equilibrium: V*2 and P*2 -Predator overexploits prey pop, driving it to extinction -predator then starves Neutral equilibrium: V*3 and P*3 -same cycling pattern as simple LV Note: Curved prey isocline made from combining Functional response 2 and density dependent prey (slide 75)
"Rosenzweig-MacArthur Predator-Prey Model"
see written notes
"The lotka-volterra model: competitive two species scenarios"
see written notes
"Tilmans Model: Competition for 2 Limiting Resources"
-Weak predation enhance diversity in unproductive ecosystems -intense predation enhances diversity only in very productive ecosystems
Impacts of predation on biodiversity
-In areas where cougars were pushed out of park, biodiversity is diminished
Impacts of predation on biodiversity: Cougars in Zion example
-dingoes introduced 3-5000 ya -considered invasive: negative effect on livestock, some native sp -extermination programs in effect -but dingos negatively effect other invasives too: feral pigs, goats, foxes, cats (more recently introduced) -other invasives linked to extinction of many verts in aus, therefore dingos are good?
Impacts of predation on biodiversity: dingoes in aus example
-succession at any site depends on which sp gets there first -no sp competitively superior to another -once original dies, site becomes available to others
Initial floristic composition
Red line: Predator 0 growth isocline Blue line: prey 0 growth isocline P*: Point of predator abundance where prey growth = 0 V*: Point of prey abundance where predator growth = 0
Insert "Predator/Prey 0 Growth Isoclines"
-more diverse assemblages have a greater probability of species that can adapt to changing conditions = more likely to survive (more common species = more likely to survive) -biodiversity insures ecosystems against declines in their functioning because many species provide greater guarantees that some will maintain functioning even if others fail -provide other species to become common when environmental conditions fail
Insurance hypothesis
-define most natural communities -include direct and indirect effects of predation
Interaction webs
-Neutral: realistic even? -Facilitation: beneficial for at least one partner, lacking any negative effects -Antagonism: at least one partner is negatively effected -Exploitation: one benefits at the expense of the other
Interactions within a community
-One species impedes others ability to compete for a similar resource type
Interference Competition
-similar resource -occurs directly btw individuals -impede foraging, survival, reproduction of another -ex) aggression
Interference Competition
-Much more energy spent on root production as opposed to shoots
Interference Competition: Blue-joint grass/aspen example
-In low disturbance, competitive dominant (r-selected) exclude other species -therefore low bidiversity -at high disturbance, only most resistant species survive (K selected), thus low biodiversity -highest biodiversity seen at an innermediate level of disturbance, where a mixture of r and K selected species coexist
Intermediate-disturbance hypothesis
-Antagonistic -Density dependent -unstable dynamic -compete for same resource
Interspecific Competition
-interaction occuring btw sp -increased abundance of sp. 1 causes pop decrease in sp. 2 and vice-versa -share a limiting resource (exploitative comp) -active interference (interference comp) -interaction is mutually negative: direct and indirect effects resulting in reduced fitness
Interspecific Competition
-blowfly experiment -control pop by provide limited food supplies to larva, unlimited food supply to adult
Introduction of time delays results in regular pop cycles
-plasticity and adaptive evolution can lead to greater invasiveness
Invasion Model
-consequences of invasions more dramatic -geographic isolation of islands limits immigration of new species -established sp evolve with few strong competitors and predators
Invasions on islands
-introduced to regions outside of historic native range -transported across barriers at increasing rate because of human movement + commerse -50000x greater rate of spread than by natural dispersal in some cases -major vectors are planes, ships, people -sometimes introduced voluntarily (hunting, fishing, biocontrol)
Invasive sp: transport across barriers
-consequences on community composition and structure -predation (most common), competition, parasitism, disease
Invasive species: Community/population level impacts
-ecological effects -social effects -financial effects
Invasive species: Potential impacts
-few invaded ecosystems are free from habitat loss and disturbance -uncertain whether dominant invasive sp are driving community change or passengers
Invasives: drivers vs passengers
-species colonization rate declines as a function of resident species richness -P = saturated local richness -sp extinction rate increases as a function of resident sp richness: increased interspecific competition, predation ressure -s = equilibrium species richness: balance of colonization and extinction rates -see written notes for graph -closer, larger = more diversity -smaller, farther = less diversity
Island biography Theory (Macarthur and wilson 1967)
-brown tree snake accidentally introduced -moved across island, preying on and eliminating native birds -birds evolved in absence of predators = flightless -predation
Island of Guam
-volcano erupted following tsunamis -Catastrophe = natural lab -ecologists studied colonization of sp -source islands, sumatra and java, ~40 km from krakatau -sea dispersal arrived first -wind dispersed grasses, ferns moved away from beach -wind driven trees, birds, bats arrived -plants dispersed by physical forces are first to arrive in primary succession
Island of Krakatau
-regulation of colonization by distance from nearest source of colonists -faster from nearby species pool
Islands: Regional regulation
-regulation of extinction rate by degree of environmental heterogeneity -larger, more diverse habitats = greater refuge from competitors and predators -see written notes for graph
Islands: local regulation
-allowed abiotically identical ponds to be colonized naturally by zooplankton for 1 yr -ponds develop communities that become increasingly dissimilar over time in terms of sp composition -biomass, density differed, sp richness remained similar -community divergence = gleason -increasingly dissimilar pond communities did not share common initial colonists = priority effects
Jenkins and Buikema 1998: Pond experiment
-Fish living in cold climates develop more vertebrae
Jordans rule
-wolves extirpated in early 1900s, reintroduced in 1995ish -lead to changes in elk grouping, foraging behaviour, habitat selection, diet, nutrition -large decline in grazing of aspen, especially in riverine areas (riparian): elk less likely to graze in areas with poor escape routes, high visibility to wolves
Keystone sp and trophic cascades: Wolves in yellowstone
Predators -strong top-down effects on structure and composition of communities -reduce comp amongst prey sp -allow poorer competitors to persist Mutualists -important plant-pollinator interactions Ecosystem engineers -bears, maggots: transport nutrients -Beavers: transform river systems, mitigate flooding
Keystones: what kind of species?
see written notes
LV Model: State-Space Graphs
-isoclines have POSITIVE slopes -unrealisticly simple: linear functional responses -suggest more intense mutualisms at higher densities
LV modelling of mutualisms: Summary
-support more species because of lower extinction rates -for islands at a given distance from mainland, larger islands will have more species at equilibrium than smaller islands
Large island/area
-examined evolutionary species-area relationship btw high diversity of anolis lizerds and sized of caribbean islands -Within island speciation rate exceeds immigration as source of new sp on islands >3000 km^2 -big islands sustain more sp, the sp come from radiation -large islands can be really remote but still have lots of diff sp -classic island biogeorgraphy theory fail..
Large islands: lasos and schluter (2000)
-mixture of evolutionary and ecological processes -determined by summing over all local processes throughout the landscape -Net number of species = speciation - regional extinction (selection) -longer time period
Large scale biodiversity (regional, gamma)
-immigration rate = primary mechanism driving increased sp richness over a range of small islands -multiplicative influence of speciation increases sp richness on larger islands -supports neutral metacommunity model?
Lasos and Schluter: speciation fuels immigration effects on species richness on large islands**
Should hook on after card 135ish
Lecture 5 start
-Optimal foraging -Organisms can only be limited by one resource at a time, this will dictate growth -Acquiring excess of non-limiting resources will not increase fitness -Species competitive ability = growth rate as a function of the resource that is least available
Leibigs Law of the Minimum
-generally considered as ecological processes -factors that determine local pop density (rare vs common) -Species richness (net number of species locally) = immigration (establishment) - local extinction (drift) -shorter time period
Local biodiversity (alpha, beta)
-sigmoidal -Exponential growth to limit (K) -results from negative feedback/environmental resistance, interspecific competition -when K reached, environment saturated
Logistic Population Growth
-intially: reduction of pop size can take place with relatively small impact on geographic range -severe non linearity of relationship of population size and range means decline can be extremely rapid -maybe not extinction, but loss of commonness: can still greatly influence ecosystem structure and function
Loss of common species: results
-Simple -nonmechanistic -doesnt completely consider resources -Pop growth dependent on pop size and limited resources ensure there is max carrying capacity (K) Used to answer: -Under what circumstances can 2 species coexist? -Under what circumstances does 1 species outcompete another species
Lotka-Volterra Competition Model
-Spatial heterogeneity -biotic interactions -dispersal -productivity These things can be effected by climate and history
Main processes determining diversity
-relationships between levels of species richness and ecosystem function -THE WAY A SPECIES AFFECTS ECOSYSTEM FUNCTION IS LIKELY TO BE PREDICTABLE FROM ITS CONTRIBUTION TO THE TOTAL BIOMASS -Common species important to: primary production + carbon storage, Bioturbation (mixing of sediment), functional stability, invasion resistance
Mass-ratio hypothesis
-match/mismatch or larval fish occurring together with their food determined whether they fed or starved
Match-mismatch hypothesis: Cushing (1974)
Alpha -local richness -number of species at a given locality/sample Beta -species turnover -rate of species change btw localities Gamma -regional richness -total number of species across a broad region -gamma = alpha + beta
Measures of Species Diversity
-large scale biodiversity (regional, gamma) -local biodiversity (alpha, beta)
Measures of species diversity
-sort species from most to the least abundant, assign rank (1 to S) -using either raw abundance or relative abundance: plot rank on X and abundance on Y in log scale -This plot shows species richness and eveness -see written notes
Measuring local diversity: Ranked abundance distributions
A function of: -species richness: number of species, simplest measure (S) -evenness -accurate species richness values are important for conservation strategies -only estimates are possible: number of sp depends on sampling effort -species richness increases with sampling effort (the more individuals you collect, the higher number of species you get) -rarefaction: common estimation method
Measuring local diversity: alpha
-rate of species change between localities/habitats -not correlated with alpha: high alpha doesnt necessarily imply high beta -whittakers species turnover -Additive model: Beta = gamma - alpha -Product model: Beta = gamma/alpha
Measuring species turnover (beta)
-species turnover vary as a function of spatial scale -larger area = more species turnover -the farther two plots are from each other, the higher the sp turnover
Measuring species turnover (beta): Spatial scale
-Key: reproductive isolation of populations -Allopatric, peripatric, parapatric and sympatric
Mechanisms of Speciation
Autogenic -within the ecosystem -within and between sp interactions alter availability of resources (nutrients, light, moisture) Biogenic -invasions of non-native, insect epidemic, diseases introduced
Mechanisms/driving forces behind succession: biotic
-static parameters (K and alpha) replaced with more dynamic variables (ex) nutrient uptake rate) -based on Consumptive competition: operate via effects of competitors on a shared resource rather than directly on each other -Differences in ability of species to grow at various levels of 2+ resources -Predicts when species will coexist -consumptive competition: resource is consumed by an individual so it cannot be used for others
Mechanistic Competition Models
-species dispersal is important to local richness -biotic factors such as predation and competition exclude species from communities
Metacommunities: Factors affecting local richness
-a set of local communities that are linked by dispersal of multiple interacting species
Metacommunity
-set of local communities that are linked by dispersal of one or more of constituent sp -patches linked via dispersal -regional sp pools from across landscape serve as potential sources of colonists
Metacommunity
-neither dispersal nor differences in species niche considered important -Random events drive community membership via species loss (extinction/emmigration) and gain (speciation/immigration)
Metacommunity Model: Neutral
-Local community: species differ in ability to disperse and flourish in the new environment -Ecological trade-offs: species A better suited to new environment but is a poor disperser relative to species B. Species B is less well suited to environment but is a superior disperser
Metacommunity Models: Patch Dynamics
-species dispersal into local environment weak for all species -species sorted into the community based on the compatibility of their niche with new environment
Metacommunity Models: Species sorting
1. patch dynamics 2. mass effects 3. species-sorting 4. neutral perspective
Metacommunity models: 2 competing sp
-dispersal is strong for all sp -sp present in both habitat/patch types -niche and competitive ability only affect relative abundance within patch -strong dispersal = rescue effect, ensures less well suited sp persist in local communty -different ability to compete at local scale, similar at regional scale -Coexistance of competing sp WITHIN PATCHES
Metacommunity models: Mass effects
-neither dispersal nor differences in sp niche considered imporant -random events drive community membership via sp loss (extinction, emigration) and gain (speciation, immigration) -see lecture 8, slide 53
Metacommunity models: Neutral
-local community assembled by species that differ in their ability to disperse and flourish in new environment -coexistence AMONG patches -ecological tradeoffs (competitive ability vs disperser -See written notes for diagrams
Metacommunity models: Patch dynamics
-species dispersal into environment weak for all sp -sp sorted into community based on compatibilty of their niche with the new environment -dispersal insufficient to offset being poorly suited for an environment or contribute to density dependent interspecific competition -Coexistence AMONG patches
Metacommunity models: Species sorting
-dispersal is strong for all species -Source-sink scenario -Strong dispersal has a "rescue effect" insuring less well suited species persists in local community -Different ability to compete at local scale, but similar at the regional scale
Metacommunity models: mass effects
see written notes!
Models of mutualisms
-view community as highly integrated superorganism -process of succession represents gradual and progressive development of community to ultimate or climax stage -clements climax community = closed system -like an organism, it arises, grows, and dies -seres are different stage of development, ultimately lead to similar climax community -linear
Monoclimax hypothesis: clements
jkl
Mullerian Mimicry
-act to diffuse competition
Multiple competitors and competition
-interaction btw 2 individuals of different species that benefits both parties -increase relative fitness of individuals of both sp -does not involve altruism -reciprocal exploitation: provides net benefits to each partner -costs and benefits vary
Mutualism
-populations of both grow/survive/reproduce at higher rate in the presence of the other -Density dependent interaction -Obligative, facultative and cheators -Resource, service, and resource-service -mutualistic symbiosis (coral + algae, evolution of eukaryotes)
Mutualism
-Protective -anemone gets protection from predators, consumes clownfish waste -clownfish gets shelter
Mutualism example: Sea anenomes + clownfish
-individuals in a pop of each mutualist species grow, survive, reproduce at higher rates when in presence of individuals of other species -each sp acting selfishly
Mutualism: Measure of Success
-protective -acacia provides home, food -ant kills, removes herbivores, removes invading vegetation
Mutualisms example: Ants and acacias
-one sp directly interacts with another sp -we focus on this
Mutualisms: Direct
-non-essential -less host-specific, more generalist mutualism: can involve many functionally interchangeable sp -at the extreme end of asymmetric facultative mutualism we find commensalism -ex) certain pollinators
Mutualisms: Faculatative
-positive effects btw 2 sp transmitted through at least 1 intermediate sp -relevant for trophic cascades, webs
Mutualisms: Indirect
-obligate relationship btw algae and fungus -algae provides photosynthetic carbs -fungi provides mineral nutrients, substrate in which to live
Mutualisms: Lichen
-heterotrophic N2 fixers and autotrophic plants -N2 fixers +: shelter, carbs -Plants +: Usable N in an N limited environment -alder has bacteria Frankia in root nodules that fix N2
Mutualisms: N2 fixers and plants
-essential to sp coexistance -if 1 sp dies, so does the other -highly evolved -less common -usually specialist mutualism -ex) mycorrhizae?
Mutualisms: Obligative
-increase in fitness of one mutualist costs the other -stability: depends on prevention of excessive exploitation
Mutualisms: Stability maintainance
-exist on a continuum: strictly obligate to totally facultative -may vary in time and space from facultative to obligate -evolutionary force: range of association dependence implies that closer relationships might benefit interactants -greater stability, opportunity to control environmental conditions through association
Mutualisms: Variance
-in one direction, currency is food -in other direction, its a benefit (dispersal) -well defined nodes of multiple sp -interaction btw, not within nodes -can show interaction strength too -high connectance, compartmentation
Mutualist ecological networks
-single sp deleted at each step, starting from most generalist to most specialist sp -sp that become isolated undergo co-extinction (fragile network) -if specialist mustualist sp removed first, effect on network is lower
Mutualist ecological networks: that weird computer model thing
-habitat structure -community composition -resource competition -population reductions, eliminations -genetic impacts
Negative impacts of invasive species: Community or population level impacts
-disturbance regimes -hydrology: alterations of water regimes -geomophological processes (erosion sedimentation) -soil chemistry
Negative impacts of invasive species: Ecosystem level
-individuals are ecologically identical -they originate at random -abundances fluctuate randomly over time -despite differences in phenotype or function, no implications for biodiversity = arise randomly
Neutral Theory
-assumes there are local communities and metacommunities -Within local communities: extinction/recolonization follow MacArthur and Wilsons theory of island biogeography -Often used as a null model, although doing so promotes duality thinking: both neutral and nonneutral factors may be present within a community -useful because one doent need to supply species-specific details about all members of a community to capture overall patterns -neutral theory is simpler
Neutral Theory: Summary
-organisms are more affected by mutation and drift than natural selection -therefore higher order patterns are largely due to stochastic factors and not biotic interactions
Neutral theory (of molecular evolution? Kimura and Crow 1964)
-Metacommunity: speciation and random change in abundance -Local community: connected to metacommunity by dispersal, drift important
Neutral theory/null model: Basic structure
-species that can withstand certain biotic conditions wind up in certain areas; these species are thus alike in certain ways -diveristy is due to unstable coexistence and the balance between extinction and speciation
Neutral theory/null model: Ecological drift
Regional effects -describe much structure of many communities without invoking biotic factors Local effects -difference btw predicted community based on regional pool and real community -presumably a result of biotic interactions
Neutral theory/null model: Local vs Regional effects
-useful to test the relevance of mutations in individuals
Neutral theory/null model: Mutation
-have we been overestimating relative importance of nice (competition etc) vs neutral processes (dispersal, drift?) -have we been overestimating the relative importance of deterministic vs stochastic processes?
Neutral theory/null model: Questions raised
-useful to test the relevance of random dispersal -see written notes for some drawings that may or may not be relevant
Neutral theory/null model: Random dispersal
-each species has a probablilty (proportional to its abundance) of randomly splitting into two daughter species (as in allopatric speciation) = assemblage of one species -tests the relevance
Neutral theory/null model: Random-fission model
-zero sum -individuals with equal probability of colonizing open space -deaths occur at a constant and fixed rate
Neutral theory: Assumptions
-to stur the scientific pot vigourously, which in my opinion has been overdue in community ecology for a long time -neutral theory has been both lauded and ridiculed: paradigm shift in the making? -has been around for 10 years!
Neutral theory: Main goal (Hubbell)
-dispersal, which influences the relative strengths of intra and interspecific interactions -just no competition/dispersal tradeoffs
Neutral theory: Mechanism of community patterns
1. Old: community structure occurs without impact of any biotic interactions. Assembly is biologically neutral 2. New: Per capita ecological equivalence of all species. They do not differ in probability of reproduction, death, migration, speciation -for a given trophic level in the food web!
Neutral theory: two possible interpretations
-applies to individuals in a single trophic level
Neutral theory: who does it apply to?
-test the relevance of random speciation in the structuring of communities -loss of species from communities by stochastic change in population size is balanced by production of new species by processes analagous to mutation or to the fission (allopatric) of populations
Neutral/Null Model uses: Random speciation
-maybe biotic factors are not so important? -Null model (H0): the hypothesis you are trying to disprove, the one that states there is no difference -neutral model is a null model because it is based on stochastic events, there is no biotic interation = random
Neutral/Null models are wrong, but they can predict community structure. Elaborate.
-n-dimensional hypervolume of environmental conditions and resources that define the requirements for a species to live and persist
Niche
-Competitive exclusion and resource partitioning results in differentiation of realized niche -Reduced competition -Increases species diversity -Competing species more likely to coexist if they use resources in different ways
Niche Differentiation and species diversity
-wiens et al 2010 -6 sp across 2 clades, evolved different environmental tolerances/niches -human impact results in loss of one clade, reduced phylogenetic diversity due to niche conservatism -species niche drives metacommunity composition
Niche conservatism and changing environment
-degree of niche conservatism among and within such groups might explain their responses to environmental changes -more closely related primary and secondary consumers show greater similarity in their response to a stressor than do primary consumers
Niche conservatism and phylogenetic relatedness
-species are often similar to their ancestor, therefore stay in envoronment they are adapted to -they can alter to fit in new environment, but it happens less often
Niche conservatism in metacommunities
-How many potential ecological niches occur -How they resemble or differ -How the species occupying different niches interact
Niche structure
-niche difference (trade-offs) lead to character displacement and adaptive radiation -species differ to better exploit their niche
Niche theory
-worlds worst invasive species -leads to extinction/near extinction of several hundred native sp -can grow 2 m in length, weigh over 200 kgs
Nile Perch
-mutualists provide each other with nutrients, food -energy obtained by 1 sp transferred to another -ex) essential macro and micronutrients
Nutritional mutualism
-explain abundance and distribution of organisms -invocation of biotic interactions -but null models often can predict community structure, biotic factors not so important?
One goal of ecology
R-strategists -Rapid growth -many offspring -early reproduction -small body size -single reproduction -weedy and early successsional species -unpredictable environment K strategists -slow growth -few offspring -later reproduction -large body size -repeat reproduction -humans, mammals -predictable environment with competition
Organism choices in resource allocation
-autotomy -playing dead
Other ways Prey avoids predation
-what sp is introduced -ecosystem -ecosystem property or processes -sp -region -time since introduction -need explicit comparison of introduced species in native + introduced ranges
Outcomes of species introduction depends on?
-seem to respind when an ecosystem is over-fished -highlights concern that the ecosystem switch that they have observes is to jellyfish biomass dominance rather than fish
Overfishing + Jellyfish
-often occurs amongst sessile species -contact or non-contact competition of a species by a larger species -restricts access to resources -Occurs later than preemptive
Overgrowth Competition
-The higher the K, the more unstable the system becomes -Biodiversity highest at intermediate levels of productivity
Paradox of Enrichment
-The more efficient (larger a) the predator, the more cyclic/unstable the interaction -K stays the same -mimics paradox of enrichment
Paradox of Enrichment by varying predator efficiency (not increasing K)
-30-40 sp of plankton coexist in temperate lakes, all compete for same resource -Seems to go against competitive exclusion principle -Possible options: environmental condition change too rapidly for equilibrium, each one has different nutrient limiting, species specific viruses
Paradox of the Plankton
-specialization along environmental gradients within continuous geographical area -Initial step of speciation: new niche entered (but still connected to original pop) -Evolution of reproductive isolation occurs in an adjacent niche
Parapatric Speciation
-Isopod fish tongue -isopod gets into hosts mouth, grabs onto tongue with 7 hooklike legs -feeds on tongue artery blood, tongue degenerates over time, parasite hangs onto stub -little effect on fish, can still hold onto prey -functionally replaces host tongue, does little other damage
Parasitism can move to commensalism: Example
-south pacific snail -driven extinct following infection with microsporidian parasite: steinhausia -parasitism -followed population decline caused by human exploitation of the shells -predation by introduced biological control agents
Partula turgida
-most numerous bird on earth -distributed across north america -overexploitation with habitat loss -altered lives of predator and prey, changing pathways of nutrient and energy
Passenger pigeon example
-2 sp coexist among patches owing to offsetting differences in colonization and competition abilities -species that will occupy patch will, in the end, be the better competitor
Patch dynamics: Importance of ecological trade-offs
-spatial variability of patchiness, suitable environment -niche partitioning -natural barriers such as rivers, mountains create patches -fire may also create patches -can also be created through human interference: oil and gas seismic lines, harvesting
Patch heterogeneity
-potential stabilizing mechanism for biodiversity in patchy environment (coexistence amongst patches) -sp have competitive hierarchy -better competitor always wins in a patch -fugitive sp (inferior competitors) coexist by being better disperser/colonizer -strict trade-offs btw competition and colonization ability -coexistence among patches, not within patches! -Autoecology of sp: trade off (competition vs colonization ability of sp)
Patchy environments: Competition/colonization trade-offs
-what we can easily observe directly -Primary: species diversity, composition and abundances -Emergent: productivity, stability, food web connectance etc -created by processes
Pattern: What is it? What kinds are there?
-Population isolation and founder effect, leads to bottle neck -Initial step of speciation: a new niche is entered -Evolution of reproductive isolation occurs in an isolated niche
Peripatric Speciation
-more than 10 million tonnes harvested -collapsed in 1972 -combination of exploitation and natural population -variability due to upwelling system
Peruvian Anchoveta example
timing of the availability of an important resource changes in response to climate but timing of the demand for a resource does not change -prey abundances can occur later than predator abundances, at the same time but not in high enough numbers or only 1 prey can occur with predator, while other occurs later
Phenological Mismatches: When do they occur?
-timing of bio events, periodic phenomena in the annual cycle of sp that affect community properties -dates of first occurrence -controlled by seasonal climactic changes, other sp and interactions
Phenology
-Plants: budbreak, flowering, fruiting, leaf fall, dormancy, frost hardiness -first flight of butterflies -first appearance of migratory birds -date of egg-laying birds and amphibia -date of spring algal bloom
Phenology: Examples
Ruderal -like r strategists -High seed production, long distance dispersal (pioneer species) -First to colonize after disturbance -High disturbance tolerance, low stress tolerance Competitor -like K strategists -Superior competitive skills for resources -low disturbance tolerance , low stress tolerance Stress tolerator -tolerance of shade, low nutrients, low moisture -late successional species -low disturbance tolerance -high stress tolerance
Plant Life History Strategies (Grime)
-species act as a community unit -supra-organism
Plant communities: Clemets
-species with individualistic responses -no communities actually exist
Plant communities: Gleason
-plant species specialize on a certain type of pollinator -common features -bee flowers, bird flowers, mammal flowers, moth flowers -evolution of a speciality
Pollination syndromes
-result from time delays in response of pops to own density -hare cycles -oscillation and time delays -oscillation may reflect intrinsic dynamic qualities of biological systems, some even with small environmental fluctuation -time delays in responses
Population cycles
-Population growth is limited by population size, per capita growth rate and carrying capacity (limited resources) -Limited by intraspecific competition
Population growth model
-Predator pop has little effect on abundance of prey pop -Predator becomes extinct -Predator eradicates prey, predator goes extinct from lack of food -Predator and prey coexist in dynamic equalibrium
Possible outcomes (4) of predation
-Extinction -behavioural resource partitioning: warblers feed in different parts of the tree -behavioural/structural resource partitioning: anoles become adapted to different parts of the tree -interspecific character displacement: cats with different tooth size for different prey -intra specific character displacement: Individuals of the same species exhibit differentiation of a specific character (beak size)
Possible outcomes of competition
-ex) antilles anolis -Adapted for life in different parts of the tree
Possible outcomes of competition: Behavioural/structural resource partitioning
-ex) mcarthurs warblers (Lec 1, slide 50) -feed in different parts of a similar habitat (tree)
Possible outcomes of competition: Behavioural resource partitioning
-ex) canine tooth diameter in various Felis spp. -Fall along a spectrum, allowing each to pursue different prey items
Possible outcomes of competition: Interspecific character displacement
-ex) beak size in sympatric sparrows -Individuals of the same species exhibit differentiation of a specific character (beak size)
Possible outcomes of competition: Intraspecific character displacement
-alter ecosystem structure -alter ecosystem function -alter biodiversity
Potential negative effects of invasives on communities?
-Common among colonizing sessile species -based at the beginning of establishment -whoever settles first gets the space
Pre-emptive or Space Competition
-Prevents it: predators allow coexistence of competing prey -Ex) Pisaster creates higher biodiversity because it preys on mussels which are a very good competitor, this allows barnacles to exist in habitat. Without pisaster, barnacles would be excluded by mussels.
Predation Effect on Competitive Exclusion
-predators can prevent competitive exclusion, allow coexistence of competing prey ex) pisaster allows barnacles to thrive alongside mussels. Without pisaster, balanus (barnacles) would be out competed by Myrtilus (mussels) and likely be extirpated. Mytilus does this to many other species as well.
Predation and Competitive Exclusion
-Non-consumptive trait-mediated interactions generate surprising effects of prey on predators Small beetles feed only on fly eggs but when aphids are present, they prefer to feed on those instead of eggs. Larger beetles do not feed on fly eggs reduce egg predation by eating smaller beetle. BUT when aphids are present, large beetles get excited and eat everything and thats bad news for the eggs.
Predation and food webs: complex non-additive interactions (beetle and fly egg example)
-Decomposers are food limited -Producers compete for resources -Predators limited by competition for prey -Herbivores are not food-limited due to the excess of plants -THUS, predation must limit herbivores because they are surrounded by food
Predation and the HSS concept
-When there is a predator in the system, population ratios similar to those where there is only a single species in the system -When predators are removed, D. tripunctata is dominant and drives other two species populations way down.
Predation vs Competition: Fruit Fly example
Apparent competition -predator mediating interspecific competition Consumptive competition -predatory competing for similar resource
Predation vs Competition: Indirect Effects
-predator eats pollinator, plant production negatively effected -Knight et al. (2006) showed that various predators suppress pollinators -Consequently, plant reproductive success is reduced by predation
Predator effect on mutualistic relationship at lower trophic levels?
-Predator/prey coevolution over long periods of time: evolutionary arms race
Predator-Prey Coexsitance
Ecological succession
Predictable change in species over time, as each new set of species modifies the environment to enable the establishment of other species
-starting from scratch, not previously vegetated -development of bare surface no plant communities have previously occupied -usually occurs after large disturbance -species need to modify environment -ex) fresh rock surface after landslide, retreating glaciers, volcanoes, mining, wars, sometimes flooding (alluvial sediments)
Primary succession
-200 yrs = short time -pirmary succession sequence likely developed quickly because: 1. Glacial till weathered easily (sandstone, limestone) 2. wet, moderate climate 3. nearly constant presence of N-fixing organisms
Primary succession: Glacier bay
-outcome depends on initial abundances of 2 sp Priority effects depend upon: -intitial pop sizes, intrinsic growth rates, carrying capacities, competitive intensity and symmetry
Priority effect: what do they depend upon?
-important for gleasons theory -divergence based on what sp arrive first -in clements convergence thing, you will end up with same climax community no matter what
Priority effects: clements vs gleason
A a level of general habitat specificity: -model is not neutral -ie only includes woodland species BUT at level of specific woodland features, woodland types, woodland sizes -model is neutral
Problems with Neutral theory/null model: Scale
-gives rise to the pattern
Process
-idea of overlaps -lose one of the internal species, the reduction in ecological function will be much lower than the rivet hypothesis -once you start to lose big player species, such as keystone, there is a rapid decline -grades the importance of species in a system
Processes determining species diveristy: Redundancy hypothesis
-disturbances (type, intensity, interval) and time since disturbance -primary productivity and ecosystem function -environmental heterogeneity/ niche breadth -intensity of inter-specific interactions -dispersal: metacommunities
Processes determining species diversity
Summary of these models
Processes determining species diversity
-blended, may or may not be independent -Speciation (evolutionary) - extinction (ecological) -Interspecific interactions and their effect on coexistence play a role, both evolutionary and ecological
Processes determining species diversity: Evolutionary vs ecological
-assumes a linear relationship between species richness and ecological function -with many species, this role will supply high function -with less species, this is a reduction in ecological function
Processes determining species diversity: Productivity hypothesis
-cannot predict the ecological function from the set of species which is there -role is unique, changes occur with the loss of gain of a species -Really want to know which species is there -low niche overlap, but species identity is important
Processes determining species diversity: idiosyncratic model
-Recruitment: proportion of juv individuals that survive and are added to a pop (closes space in a community) -Direct consumption: predation/herbivory (opens space in community)
Processes influencing predator-prey interactions: spatial context
-airplane rivet analogy: a few rivets wont matter if lost, but there will be a time when there are enough missing to cause a plane crash -High ecological function with lots of species overlap -Remaining species will somehow take the part = redundancy -Not as dramatic a decline as previous -species identity unimportant, redundancy key
Processes of determining species diversity: Rivet hypothesis
-ecological rates that maintain ecosystems: functioning per unit time -C/Energy assimilation rates: productivity -must be greatest at lowest trophic level, offset inefficiency of energy transfer -inverted productivity pyramid = ecosystem collapse (overstocking oligotrophic lake with trout)
Productivity pyramids
-Spatial structure: way species are distributed relative to each other -Temporal structure: timing of the appearance and activity of a species -Species richness: number of species in a community -Species diversity: number of species in a community and their relative abundances -Trophic structure: interactions among species of different trophic levels -Scale: well defined area -Succession and disturbance
Properties of a community
-active or passive defense of one mutualist by another -guarding behaviour -ex) clownfish + anenome ants + acacia
Protective mutualisms
-degrades wetlands -decimate and chokes out native plants -single plant can produce >300 000 seeds
Purple loosestrife
-Resource level in environment at which population growth rate = 0. -When 2 species are competing for same single limiting resource, sp. with lowest R* always wins. (lowers resource availability, gives second sp negative growth rate, drives them to extinction.)
R*
-no competition -no differences among species -no environmental differences or gradients -no niche concept -all have same opportunity to exploit same niche -certainly wrong, but it can work! -see written notes for a visual representation
Radically neutral model
-climactic + soil conditions -Frequency/severity of disturbance -degree of environmental change needed before one community can replace another -productivity, efficiency with which organisms produce environmental change -longevity of dominating organisms -degree to which community can occupy, dominate site, resist invasion -importance of priority effects
Rates of successional change depend on?
-limited support in some ecosystems for strict colonization/competition tradeoff, local extinctions/recolonization of fugitive sp -other ways for coexistence to occur across a landscape
Real world: coexistance tricker
-generally narrower ecological space due to inter-specific interactions -set of conditions under which it occurs in nature
Realized Niche
-larger clutches of eggs/litters in cold climates than in warm climates
Renschs rule
Avoid harsh climactic conditions = environmentally vulnerable phenophases coincide with favourable climactic conditions Avoid times when resources are scarce = phenophases with high resource demands coincide with high resource availability Minimize interactions with antagonists = phenophase displays maximize interactions with mutualists
Requirements for survival + evolutionary adaptation
-Role of competition: along gradients of resource availability (limiting resource) -Species with lowest resource demands = most competitive conditions required (tolerated) for establishment and growth to maturity -Resource allocation strategies: above vs below ground (root/shoot strategy), reproduction vs defence (herbivory)
Resource-Ratio Hypothesis (Tilman)
-most at risk -closed system, when something gets in it changes things quickly -ex) great lakes: all the crap that came in on ballast
Risk of invasion: Lakes
-during outbreak: 15 trillion individuals -distributed western USA, btw mississippi and rocky mountains -other times: largely restricted to valley of the rocky mountain regions (although large numbers) -just in a few years: one of the most serious agricultural pests to extinction
Rocky mountain grasshopper example
-Predator efficiency (a) -Conversion rate (e) and/or -Predator death rate (s)
Rosenzseig-MacArthur Model: Determining Predator Isocline
-Both predator and prey can go extinct if predator is too efficient at capturing prey or if prey is too good at getting away -Predator can go extinct while prey survives: predator not efficient enough even with prey at K -Capture efficiency in balance: coexistence btw predator and prey -Coexistence without cyclical dynamics: predator relatively inefficient, prey remains close to K Coexistence with cycles: predator more efficient, regularly bring down prey density to level predator nees to maintain pop size
Rosenzweig-MacArthur Predator-Prey Model: Possible Outcomes
-multiplied so quickly that there are now >100 per square meter on some lake/river bottoms
Round Goby
Single large or several small reserves? debate Single large -preserves intact communities and maintains viable populations (esp those at low densities, large species) -many cons: applicability, how large is enough, disturbances, economic constraints Several small -lower S due to smaller fragmented area, bu overall may increase S at the larger area. Potentially encompasses higher landscape heterogeneity -many cons: scale, fragmentation, habitat loss, edge effects, connectivity, loss of interior species, invasive sp etc
SLOSS
-millons of individuals occurred in steppe grassland semi arid desert of russa and central asia -illegal hunting of horns, meat -resulted in highly skewed sex ratio = reproduction collapse
Saiga antelope example
-WTF -see written notes
Schematic representation of metapop theory
-stowed away on cargo ships from atlantic ocean -present in all 5 great lakes -bloodsucking: can kill more than 18kg of fish (12-20month adult life cycle)
Sea lamprey
-environment more friendly to be colonized -previously vegetated -ex) after flooding, agricultural clearing, fire, herbivory, windstorm
Secondary succession
-manipulated total abundance and relative abundance of two damselfly sp -compared per capita mortality and birth -related sp showed no separation in niche preferences along potential important niche axes -No patterns seen: no clumps of the same species together -same thing seen in the death figure -also no correlation seen in relative abundance of each sp figure (lecture 12, slide 38)
Siepielski 2010
-lynx breed and reproduce until hare runs out -hare flux still occurs with hardly any linx -Lynx pop controlled by hares veg supply -lynx must turn to other prey when hares die off, but are picky -hare pops recover with recovery of veg + lack of predators -lynx pop grows in response. New cycle!
Snowshoe hare and lynx Population cycles
-employment and community stability, recreation, aesthetic/spiritual values, public perception
Social effects
forgot until now
Sooo go back and check full slides until beginning of food webs
-species richness increases with area, like it increases with sampling effort -the rate of increment in S is also a measure of beta diveristy -the more area you cover, the larger amount of sp you get -see written notes
Sp diversity in space
-can change competitive outcomes -1 sp dominated one end of gradient, other dominates the other end, coexistence occurs in between
Spatial heterogeneity: Gradients (clines)
- A group of morphologically similar creatures, which can: ○ Interbreed to produce fertile offspring ○ Are 'reproductively isolated' But how about... - Subspecies, asexual/vegetation reproduction, hybridization, parthenogenesis (w/o male), autogamy? - Horizontal gene transfer, binary fission? - Extinct 'species'? Morphological (typological) species concept - Differs in characters, traits - Ex. Huge difference in male/female spider genitals Phylogenetic species concept - Differences in lineages (evolutionary monophyly) - Parent species goes extinct and give rise to two separate species Genetic species concept - Differences in DNA (barcoding) Ecological species concept - Differences in niche space
Species Concept
-number of species contained (richness) combined with abundance of individuals within each species (eveness)
Species Diversity
-fecundity: ability to produce abundant, healthy offspring -areas with high patch density: more fecund sp will do better -areas of low patch density: better disperser will do better
Species coexistence in real world: Dispersal/fecundity trade off
-species increase with area -species decrease with isolation
Species diversity in space: Fundamental principles in theory of island biogeography
-Measure of how equally abundant species are or how individuals are distributed among species -most divers = resources partitioned evenly among the species
Species eveness
-common species tend to remain common -rare species tend to remain rare
Species stability on ecological and evolutionary time scales
-majority of species have small geographic ranges -relative narrow range of environmental conditions -except steep environmental gradients such as mountains, lakes
Species: General geographic ranges
-fragmentation consistently suppressed capture rates of only common insectivorous bird sp -uncommon bird sp stable -common sp are better competitors, therefore uncommon sp already forced to live in patches. Patch creation does not effect them
Stouffer and Bierregaard Results: Common vs uncommon sp
-fragmentation significantly reduced bird sp richness -island size effect: greatest negative effects in small 1 ha patches -matrix-dependent effect: island effect differed depending on type of surrounding vegetation -matrix = inter-habitat space -better habitat had less impact, larger habitat had less impact
Stouffer and Bierregaard Results: Patch size, tree sp
-environment less suitable for early sp, more suitable for late successional sp -early successional sp die out -eventually resident sp are only ones that do not change environment in a way to favor others
Succession: Facilitation model
-environment less suitable for establishment by sp -resident sp inhibit establishment of all other sp -persist until disturbance
Succession: Inhibition model
-communities not super organisms, nor laws unto themselves -Clementsian pattern of repeatable associations does hold in some cases -succession: no longer believed to be a linear or predictable process -unlikely that single theory applies
Succession: Modern view
-environment less suitable for early sp -neither less nor more favourable for later successional sp -eventually resident sp are ones able to tolerate environmental change by earlier sp, no other sp can tolerate conditions
Succession: Tolerance Model
Early successional sp -high growth rate -small size -high degree of dispersal -high rates of pop growth Late successional sp -low rate of disperal -slower growth rate -larger -live longer
Succession: rocky intertidal
-generally beneficial -intimate, persistant interaction btw sp -living together of two or more organisms of different sp
Symbiosis
-genetic divergence within the same geographical area -initial step in speciation = genetic polymorphism -Evolution of reproductive isolation occurs within the population
Sympatric
-population fluctuations -gyre falcons, sheep, plankton
Temporal dynamics of populations
-annual changes in abiotic conditions drive phenologies of factors affecting plankton -competitors are separated over time according to differences in competitive ability and sensitivity to predators -differences nin sp phenologies minimizes competition, enhancing coexistence and diversty
Temporal heterogeneity of ecological factors and competitors
-timing of the appearance and activity of species
Temporal structure
-not static, change over time -variable interaction btw long lived predators, short-lived phenologically separated prey -ignoring temporal variation: overestimates number of taxa that interact at a certain time, level of connectance at a given time
Temporal variation in food webs
-affects age structure of pops -variation in pop size over time often leaves its mark on age structure -age structure influences rate of pop growth -age distribution of forest trees show effects of disturbances on seedling establishment
Temporal variation: pop age structure
-Mobile species exhibit aggressive behaviour to protect habitat
Territorial Competition
-2 dominant exotic grasses with 50-80% total cover -treatments: biomass reduction (mowing), complete removal (weeding) -measured native sp richness + abundance for 3 years
Testing driver vs passenger: exotic grasses
-rapid + persistent decrease in total production -gradual shift in dominance from perennial grasses to perennial forbs (mostly by natives still present) -1/2 sp = no change or decreased significantly in cover following exotic dominant removal -recruitment limitation of native sp more widespread explanation than was competitive exclusion -driver passenger model mostly supported
Testing driver vs passenger: results
-Measures total number of resources in an environment -Resources found in environment or in living organisms -Characteristic of an environment, can be measured
The Resource Supply Point (S)
-Realistic compared to LV model -Logistic prey growth in absence of predators (add K for prey) -Predator capture rate determined by handling time and satiation (Functional Response type 2)
The Rosenzweig-Macarthur Model
-more diverse assemblages = greater probablity of containing sp that are adapted to changed conditions
The insurance hypothesis
dP/dt=Change in number of predator P=Predator pop size e=conversion of prey into predator a=attack rate per predator s=starvation induced death rate V=prey pop size
The lotka-volterra predator-prey model: Predator (P) response
dV/dt=Change in number of prey V=Prey pop size b=per capita birth rate P=predator population size a=attack rate per predator
The lotka-volterra predator-prey model: Prey (V) response
-Similar sp can coexist because highly dispersive but weak competitors can colonize and persist in sites not occupied by slower, superior competitors!
The spatial competition hypothesis
-mountain tops, fragmented remnants, lakes in a land matrix and patchy habitats can all be seen as islands -conservation and management -design of nature reserves, protected areas -understanding about the effects of habitat loss and habitat fragmentation -understanding about patterns of diversity at different spatial scales -many limitations
Theory of island biogeography: Applications
-Diversity reflects a balance between processes that add vs remove species to/from pool -removal of species: extinction (evolutionary, long term), emmigration (ecological, short term) -Addition of species: speciation (evolutionary, long term), immigration (ecological, short term)
Theory of island biogeography: Equilibrium Theory
-a function of immigration rates on a regional scale vs extinction rate on a local scale -populations are in constant turnover -richness is constant but not IDs -see written notes for more
Theory of island biogeography: number of species
-Species with larger geographic range persist longer 3 types of risk spreading -metapopulations (broad range of pop size): reviving of local pops (rescue effect) -temporal (broad range of pop size) -within generation (smaller pop)
Theory of risk
-Biological legacies -left behind after a disturbance -important for determining successional pathways -Organisms: whole organisms, propagules -Organic matter: dissolved and particulate -Structures: snages, logs, coarse woody debris, large soil aggregates, termite mounds -Patterns: root mounds/channels, burrows
Things left behind after a disturbance from individuals
Harbour porpoise, european bison, american burying beetle, atlantic cod, big-leaved mohogany, white-rumped vulture
Threatened common species examples
Habitat loss, fragmentation, invasive species, over exploitation, climate change, overpopulation, pollution etc
Threats to biodiversity
-one sp enables establishment of another -important in primary succession, less so in secondary -may operate through: enhanced invasion ability, amelioration of environmental stress, increasing the availability of resources (N-fixers)
Three Pathways Model: Facilitation
-ability of a sp to tolerate low resource levels -sp can alter environment but have little or no effect on subsequent sp
Three Pathways Model: Tolerance
-plant strategies determine their roles in succession -almost always occur together but differ in relative importance -facilitation, inhibition, tolerance
Three pathways model
-one sp hinders establishment of another ex) rapid growth of one sp displaces another, allelopathy -effects may be short or long lasting
Three pathways model: inhibition
-trade-off btw rate of colonization and ability to compete for use of N (R*, limiting resource) -Species that are better competitors (lower R*) are slower to colonize -some sp establish well: large numbers in very little time -but as time goes on, they are displaced by better competitors, whose numbers significantly increase as time goes on
Tilman grass competition in abandoned agricultural fields
-Competition important everywhere -species differ in ability to acquire different resources -Trade offs: Good competitor for one resource, probably not as good for another
Tilman summary
-Most cited ecologist of the last 20 years or so -Resource-Ratio Hypothesis
Tilman's Model of Competition for Resources
-Needs to be a resource level in the environment at which the growth rate of both species is equal to 0 -Can only happen if ZNGIs intersect
Tilman's Model: 2 Resources, 2 species. When is coexistence possible? (see written notes for diagrams)
-Show change in resource availability caused by consumption -Total consumption depends on: consumption of individual and number of individuals -Characteristics of species and have to be measured
Tilman's Model: Consumption Vectors (see notes for diagrams)
-Measure rate of supply of resources in the environment -Depend upon: current resource levels, resource supply point (s)
Tilman's Model: Supply Vectors (see notes for diagrams)
-phenology -seasonal succession: timing of biological reactions, may influence priority effects -timin of sp arrivals affect prey availability, predator prey interactions, inter-specific competitive interactions
Timin of biological reactions, activities
-higher trophic levels control abundance of those trophic levels below them and/or overall ecosystem structure (trophic cascades) -nutrient supply and primary production determine ecosystem structure
Top down vs bottom up
-plants = fundamental control of higher trophic levels via primary productivity, structure, chemical components -feedback loops mediate relative importance of bottom-up control of trophic levels
Top-bottom vs bottom up effects in food webs**
-reproduction (number of offspring, number of eggs laid, number of eggs hatched, hatchlings making it to fledglings) decreased when exposed to predator playback
Trait mediated predator prey interactions: Songbird experiment
-predation risk -individuals may not be killed by predator, but almost all experience chronic effects of predation risk -Reduction in: growth, maturation rate, survivorship, fecundity, population density
Trait mediated predator-prey interactions
-non-consumptive dynamics often linking a community of species
Trait-Mediated Interaction
-Dispersal of prpagules (seeds), gametes (pollination), whole individuals (hitch a ride) -animal moves pollen btw flowers, seeds to new location, recieves nutritional reward
Transport Mutualism
-massive radiation of angiosperms during cretaceous: due to evolution of mutualistic association of plants w pollinators -evolutionary trend: towards increased specialization on one or a few pollinator species -facultative to obligative: lead to pollination syndromes
Travel Mutualisms: Pollination/dispersal evolution
-change in abundance that propagates beyond the 2 trophic levels -keystone cascades often associated
Trophic Cascade
-Positive trophic cascade effects of wolves on vegetation also involve non-predation species interactions
Trophic Cascade/Biomanipulation: Banff National Park Example
-Manipulation of productivity and food chain length -decomposing litter in 3 holes supports mosquito, dragonfly larvae and tadpoles -higher productivity=increased # sp., # trophic links and food chain length
Trophic Efficiency Hypothesis: Jenkins
-predatory fish enhance fecundity of shoreline plants via affecting a mutualistic interaction -fish release pollinators from predation by dragonflies -visitation and cross-pollination increases -landscape-level processes drive local interactions
Trophic cascade across ecosystems: Knight et al 2006
-wolves: positive trophic cascade effects on vegetation -also involve non-predation species interactions -wolves cut down elk numbers, allowing aspen and willow to flourish -this also had a positive effect on other animals such as beavers and birds -strong direct effects on elk produced strong indirect effects on plant growth, and other animal densities
Trophic cascade and terrestrial biomanipulation: Banff national park
-fluxes of organisms across ecosystem boundaries effect community dynamics -interactions affecting local predators in a system also influence interactions in other systems
Trophic cascades across ecosystems
-strong direct interactions lead to strong indirect links from top to bottom of the food web -thus, trophic cascades can short-circuit a food web
Trophic cascades: interactions
Within a trophic level, energy taken can be: -passed on to next trophic level -stored in detritus, passed on to decomposers -converted to heat by inefficient chem rxns, radiated by warm bodies, friction
Trophic energy transfer
-discrete group of organisms: share common diet, positition in ecological network -fails to acknowledge confounding influence of consuming multiple food items (omnivory)
Trophic levels
-sequence of plant, animal and microbial communities in an area over time -Process of change by which biotic communities are replaced and by which the physical environment is altered over time
Two ways of thinking about succession
-Batesian Mimicry: Looks like toxic model but is not toxic -Mullerian Mimicry: Looks like toxic model and is toxic
Types of mimicry
-levins model -all pops are similar in size, type -all may go extinct -all have colonization potential to re-establish -see written notes for picture
Types of spatial structure: Classic metapopulations
-large mainland patch with low risk of extinction -surrounding pops supported by immigrants from mainland -surrounding pops with higher risk of extinction
Types of spatial structure: Mainland-island (source-sink)
-extinction not balanced by recolonization (extinction > colonization) -no dispersal btw patches -isolation, vulnerable -eventually can lead to regional sp extinction
Types of spatial structure: Non-equilibrium
-individuals within single interbreeding pop clumped in space -clumps do not exist as separate pops -high dispersal btw patches -no extinction
Types of spatial structure: Patch dynamics
-Xenarch: dry -Mesarch: between water and sand -Hydrarch: water -oligotrophic: nutrient poor -mesotrophic: moderately fertile -Eutrophic: nutrient rich
Types of succession
-Strength -Associate with other predators -Blend with surroundings -Use of venoms, poisons -Trapping devices
Ways predator can increase efficiency?
-strength -aggregation -crypsis -venoms/poisons -armor -mimicry -behavioural strategies
Ways prey can increase predation avoidance
-Broad environmental tolerance -local adaptation
What allows invaders to invade?
-species abundance distributions -species area richness relationships -beta-diversity -ETC -Neutral theory just does as good a job as niche theory in many tests
What can neutral theory predict?
-predict which species or trails should be abundant -Predicting under what environmental conditions some species increase which others decrease -Does not include spacial structuring of regional pool -not al species are as likely to invade a given woodland -NEUTRAL THEORY MOST RELEVENT WHEN LOOKING AT SOMETHING SPECIFIC (TYPE OF WOODLAND AND/OR WOODLAND FEATURES
What can't neutral theory do?
Competitive effect of other species will suppress performance below the true R*, resulting in it being overestimated -R* will be higher because effect of competition will cause organism to grow at a higher resource availability than it actually needs, because it is stressed from competition
What happens if you grow population with inter-specific competitors and measure R*?
-Random speciation and extinction -Community changes driven by stochastic rather than deterministic processes -Ecological drift (random changes in species abundances) result in unique communities over time.
What influences biodiversity in Neutral Theory?
Non abundant species with greater than expected impact on ecosystem functions via a chain of interactions. -disproportionate effect on its environment relative to biomass -removing a keystone sp usually leads to trophic cascade
What is a keystone species?
-area where the organism inhabits -role or function of an organism in an ecosystem -interactions of a sp with all biotic and abiotic factors -how an organism lives and its position in its habitat
What is a niche?
It is a measure of the variety of organisms present in different ecosystems. This can refer to genetic variation, ecosystem variation, or species variation (number of species) within an area, biome, or planet.
What is biodiversity? Final start study
-produces a distribution of expectations within which most communities fall, rather than generating a community identical to that in any one place -we want generality, because it is applicable
What is good about the neutral model?
-Two species competing for same resource cannot exist indefinitely
What is the competitive exclusion principle?
-R strategist: high reproduction rates, high growth rates -Fewer natural predators: islands in particular -adaptable -really good competitors
What makes a non-native an invasive?
-high resistance to environmental change -returns to previous state after a disturbance (resiliance).
What makes food webs stable?
Oceans, mountains, deserts, large lakes -but not all barriers hold all species
What prevents species from dispersing globally?
Selection (predation also part of selection)
What process does competition belong to?
-Climax community -typical sequence: herbs, shrubs, deciduous trees, coniferous trees (climax)
When ultimate association of sp is achieved
-extreme environments -Neighborhood habitat amelioration: mutualisms take edge off hash conditions in unproductive systems -Associational defense: inedible mutualist can protect against intense predation in highly productive systems -interspecific competition precludes mutualisms in moderately productive systems
Where are mutualisms most common?
-island biogeography (another neutral model) -only sizes and distances of islands is important: no differences among sp -logical consequence: random collection of sp
Which earlier neutral concepts did Hubbell build on?
-Pollination, predation, competition
Which interactions determine species diversity?
-see written notes
Whittakers species turnover
-property at a "lower" hierarchical level of organization is responsible for patterns at higher levels -contributes to ecosystem function, structure and integrity
Why do we need biodiversity? Functional value
-cultural, social, awsthetic and ethical value -Religious and social value of individual species or believe that communities are valuable because they exist
Why do we need biodiversity? Intrinsic value
-potential -undiscovered species will provide benefits to future generations -drugs from microorganisms + plants -unknown roles of species to the maintenance of ecological stability
Why do we need biodiversity? Seredipitic value
-Subsistence/commercial benefits of individual sp, communities, ecosystems, genetic diversity -ecosystem services: four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and crop pollination; and cultural, such as spiritual and recreational benefits -great benefit to human civilization and quality of life
Why do we need biodiversity? Utilitarian value
-predicting the future -restoration -management
Why do we need to understand how communities change over time?
-evolutionary escape from mutualistic costs -but cheating has not replaced all mutualisms -this is because mutualism is already mutual exploitation!
Why has cheating not replaced all mutualisms?
-powerful evolutionary force -by forming a relationship, capabilities of both partners added together -faster than "slow" evolution of new capabilities
Why have mutualisms become widespread/occured for long time?
-knowing sources of mortality (starvation, disease, predation) helps understanding of community structure -Pop dynamics not understood without considering natural enemies
Why study predation?
-Control: pests, weeds, disease, invasive species -Management: fisheries, game, conservation
Why understand how much natural mortality occurs?
-choice of focal species to investigate spatial patterns with larger range -greater contribution of widespread species matches relative strength of intraspecific patterns
Widespread species used to investigate spatial patterns
-absence altered age-class distribution: overbrowsing -heavy bark damage from elk on lower meters of each tree -long term lack of recruitment (tall saplings, small diameter trees missing) -ongoing aspen recruitment occurs when elk are prevented from overbrowsing
Wolves in yellowstone: effect on aspen
-feed on phytoplankton that nourish filter feeders which supports diets of larger fish -outcompetes other species and affects the local food chain -impact of bottom trophic levels to the top
Zebra mussels
-competition -eliminated native unionid mussels from lake st clair
Zebra mussles
When population growth = 0 -Predator (P) isocline: Prey (V*) population in which predator population does not change/growth rate = 0 (dP/dt=0) -Prey (V) isocline: Predator (P*) pop in which prey pop does not change/ growth rate=0 (dV/dt=0)
Zero Growth Isoclines (go to written notes about different predator/prey LV models)
-Depends on -Resource level: supply rate and consumption rate of the resource -Population growth rate: reproduction and mortality rate of the species
Zero Net Pop Growth (competition for limiting resources)
-constant resource availability implies constant community size -therefore gains in the abundance of species must be balanced by losses in the abundance
Zero sum assumption
Fugitive Species
-competitively inferior -coexist by being better dispersers -can colonize open patches
Heterotrophs
-consumers -feed on producers to live -scavengers, detritivores, herbivores, carnivores, omnivores, decomposers
Invasive Species
-does not naturally occur in a specific area and whose introduction does or is likely to cause economic or environmental harm -can reproduce, is viable and is a threat -outcompetes native species when introduced outside of its natural environment
Ecological Resilience
-elasticity or the rate at which a system returns to a reference state following a perturbation -low resilience: system may never recover to their original state and are readily converted to new state
Guild
-group of species that use a similar resource in a similar way
Dominant species
-more numerous than its competitors in an ecological community -makes up more of the biomass
Exotic Species
-non-indigenous organism that has been introduced either accidentally or deliberately to a new location -no viable population, do not reproduce here
Indicator species
-not a keystone sp -indicative of ecosystem health, biodiversity or other properties of interest -butterflies, bats, ampphibians -defineds a trait or characteristic of the environment -may delineate an ecoregion or indicate an environmental condition such as disease outbreak, pollution, species competition or climate change
Flagship species
-not a keystone speces -representitive poster species of an area -not a whole lot of science behind it -pandas, elephant, orangutans etc
Foundation species
-not a keystone species -a dominant primary producer in an ecosystem in both terms of abundance and influence ex) kelp forests, coral reefs, trees etc
Umbrella species
-not a keystone species -protecting it protects a lot of other species too -selected for making conservation related decisions, typically because protecting these species indirectly protects many other species
-GENERALITY -depends on the focal taxonomic group (ex) bermans rule applies well for mammals, but not so much for other animals)
-pattern displayed by more than 50% of species studied
Autotrophs
-producers -use E in sunlight: convert H2O and CO2 into glucose -Chemoautotophs: get E from inorganic compounds, live where there is no sunlight
WHAT IS ecology?
-study of the processes influencing the distribution and abundance of organisms, interactions among organisms, and the transformation + flux of energy and matter
Microbial loop
-sustains many marine food webs -occurs in terrestrial food webs in soil, different players -basic loop that sustains all food webs in marine systems -dissolved organic matter used by bacteria, eventually brought up to higher players
-consumption vectors -Resource supply point
2sp, 2 R (intersecting): Outcome depends on?
-intraspecific, interspecific, assemblage -common species provide spatial and temporal continuity and often exhibit some of the classical patterns in different parts of the world
3 general spatial sets
-Speciation -Dispersal -Drift -Selection
4 kinds of processes can change the distribution, diversity and abundances of species in a community?
1. Consumptive 2. Preemtive 3. Overgrowth 4. Chemical 5. Territorial 6. Encounter
6 proposed mechanisms of competition? (TOPECC) ** See exam answers!
People think about charismatic species when they think of biodiversity But this species-scape gives the proportions of species Most as insects, mollusks, fungi (woooooot), and arachnids
A species-scape
Rarefaction
A way to compare species richness values among sites by standardizing sampling effort
-structure of a habitat or landscape influences relevant ecological processes -Abiotic spatial heterogeneity: habitat quality, resource availability, predation risk dispersal barriers
Abiotic spatial heterogeneity
-choose a strategy at random from a fixed distribution -probability for the individual to use a specific strategy evolves to match the probability for that kind of weather -determine whether to behave according to, for example, a dry year or a wet year specialist
Adaptive Coin flipping
-Verhulsts pop growth model (rN(1-N/K), where carrying capacity (K) is now being considered -dV/dt = bV(1-V/K)-PaV -Birth rate, which is a function of intraspecific competition (prey density) and environmental limitations (carrying capacity) and death rate, which is a function of predator density -Oscillations dampened over time, equilibrium switches from neutral to stable equilibrium -Logistic prey growth in absence of predators
Adding density dependence to LV model
-fire -floods -drought -large herbivores -volcanoes -avalanche -human activity
Agents of disturbance: Examples
-extremity size depends on latitude -animals living in cold climates tend to have shorter appendages -ex) rabbits in the arctic have teeny ears compared to those in warmer climates
Allens rule
-changing the environment by transforming the living or nonliving -one physical state to another by mechanical or other means -beavers
Allogenic engineers
-barrier formation creates physical separation -evolution of reproductive isolation occurs because of physical isolation
Allopatric Speciation
-Interspecific competition -Two (or more) species that share a higher trophic layer
Apparent Competition
-Two or more species share a higher trophic player
Apparent Competition
-common species are in widespread decline but little attention is paid to them -heart of the biodiversity crisis -vulnerable: land-use change (habitat loss), large scale overexploitation, invasive species (attack common species right away) -COMMON SPECIES LIE AT THE HEART OF THE MOST MARKED CASCADE OF POP DECLINE -because involved in engineering environments and biotic interactions, their decline has several impacts
Applied dimension of commonness
-examined how destruction of tropical rainforests into small islands effected communities -Whole system experiement: replicate intact forest islands monitored for bird sp before and after deforestation -BACI design: before-after comparison of impact
Applying island theory to other ecosystems: stouffer and bierregaard 1995
-invaded communities interact -native sp limited/excluded by COMPETITION from exotic dominants -better use of resources (R*) than native sp -enemy release: escape from native predators -less predators in new range
Are invasives drivers of ecological change?: Driver model
-invaded communities primarily structured by non-interactive factors (environmental change, habitat disturbance) -less constraining on invasives -leads to dominance compared with natives -invasives are opportunistic -habitat modification drives native sp loss -indirect effects
Are invasives drivers of ecological change?: Passenger model
-grow up to 1.3 m long, 50 kgs -multiplying rapidly though Mississippi, Iowa and illinois river systems -10 km downstream from Lake Michigan
Asian Carp
-attacks hardwood trees -brought to NA in packaging materials used in shipping
Asian long-horned beetle
-increase in range size with latitude -wolf in southern region will have smaller range size than one in the north
Assemblage Ecogeography Rules: Rapoports Rules
-switch from pelagic to benthic/direct dominant mode of development of marine invertebrates -benthic marine invertebrates at low latitudes tend to produce large numbers of eggs developing to pelagic and widely-dispersing larvae, whereas at high latitudes such organisms tend to produce fewer and larger lecithotrophic (yolk-feeding) eggs and larger offspring, often by viviparity or ovoviviparity, which are often brooded.
Assemblage Ecogeography Rules: Thorsons rule
-patterns in the structure of assemblage occuring in different places -often based on species richness -number of different functional or behaviour groups -Frequency distribution of traits (body size, geographical range)
Assemblage Patterns
-areas closer together are likely to experience similar environmental conditions -areas closer together are likely to share more species -widely distributed species contribute most to assemblage and spatial turnover (if you are widely distributes, you are less likely to be connected = higher turnover)
Assemblage Patterns and spatial turnover
-total abundance -total biomass -total energy use
Assemblage Patterns: Size and Abundance
-prey exponential growth in absence of predators -No density-dependence -Functional response is non-linear and asymptotic
Assuming Type 2 Functional Response and no density dependence
-Exponential growth of prey -Negative exponential death of predator -No density dependent factors
Assumptions of LV Model
-Density independent -Prey and predators respond instantaneously to changes in each others abundance (no time lags) -No resource limitation exists -Only predation limits prey -Predators only limited by prey abundance -Absence of competition (inter/intra) -Unlimited exponential prey growth when no predators are present -Predators die at exponential rate, only offset by conversion rate
Assumptions of Lotka-Volterra Predator-Prey Models
-introduced for hunting purposes -now causeing huge erosion problems
Australia: Rabbits
-changing the environment through their own structures -living or dead structures -ex) trees, common species
Autogenic engineers
-body size depends on latitude -increase of size of a species in cold temperatures compared to warm temperatures, where species tend to be smaller
Bergmans rule
Inidividuals living in unpredictable/variable environments try to maximize long term fitness by using generealist tactics. Since the environment is constantly changing, they cannot rely on specialist techniques. Looking for long term fitness as opposed to year-year fitness.
Bet-hedging (Temporal)
Neotropical, nearctic, palearctic, ethipian, oriental, australasian
Biodiversity realms
-best apply to largely inedible plant systems: forests, nutrient polluted lakes -inverted: reflect highly productive ecosystems containing very edible primary producers (ex: peruvian upwelling)
Biomass Pyramids
-territoral behaviour, local interactions, competition for space/nutrients/light, predation, disease transmission, local dispersal
Biotic spatial heterogeneity
-based on detritus -begins with dead material -energy re-used through nutrient recycling ->90% energy moves through -connected to green/grazing food webs
Brown Food Webs
-generalist species, are both locally common and widely distributed -specialists are constrained to have narrow distribution and tend to be locally uncommon -generalists more tolerant to environmental conditions
Browns hypothesis
-increases in mesopredators, decline of mesopredator prey -aka increase in herbivores, decline of plant pops
Cascading effects of loss of top predators
-Connectedness web: shows feeding relationships among organisms -Energy flow web: connections quantified as energy fluxes -Interaction webs: include type of relationship (+/-), and often interaction strength, based on experimentation (sp removal), most food webs with many weak links and few strong links
Categories of food webs
-Source: single prey based web -Sink: single predator based web -Community: complete representation of all predator-prey interactions defining a community
Categories of food webs
-Distribution of individuals: stochastic process and ecological traits (interaction with environmental conditions) -complex interplays between the traits of species, environment and the spatial and historical dynamic of both
Cause of commonness
-Eltonian pyramid of numbers: allometric pyramid -inverse relationships btw trophic level, average body size, pop density, diversity -better descriptor of aquatic than terrestrial food chains
Charles Elton: Food chain pyramids
-unstable: could also be considered competition/parasitism -organism that receives a benefit at the expense of another organism -mutualistic relationships btw two organisms, other sp try to exploit it for own benefit -cheaters common: natural selection favours cheating
Cheater species
-early cheaters exploit mutualism, plant finds a way to stabilize relationship -another wave of late cheaters, plant must once again respond
Cheaters: Feedback loop in Yucca moths
Antibiosis: chemical interactions btw organisms -antibiotics in competing fungi -insects with chem interference (ants) -plants with chem unpalatable to prey Allelopathy antibiosis: btw plants -root exudates which adversly affect growth and survival of surrounding plants -an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms.
Chemical competition
-Bergmanns rule -allens rule -glogers rule -jordans rule -fosters rule -renschs rule
Classical examples of ecogeographical rules
-spatial patterns in traits in individual species: covariation with positional and environmental variables -Impacts: morphology, physiology, life-history, population dynamics and genetic variation
Classical patterns: interspecific and intraspecific
-fundamental unit of organization exists in nature -community exists as integrated unit or superorganism -associations of plants and animals = distinct entities
Clemens and Tensley: Community School
-climate warming = ~2C over past 40 yrs -earlier spring conditions -fast growing phytoplankton (diatoms) closely track earlier spring conditions, (nutrient availability) -larger, slow growing zooplankton like daphnia unresponsive to early spring conditions -reduced energy transfer to higher trophic levels rsults -negative causal relationship btw duration of mismatch and zooplankton production
Climate-induced phenology: trophic mismatch
-communities ordered along a continuum index -continuum index: scale of environmental gradient based on changes in physical characteristics or community composition along gradient -climax vegetation actually represents continuum of forest types
Climax communities: Continuum of vegetation types
-support more species because of higher immigration rates -for islands of a given size, closer islands will have more species at equilibrium than farther ones
Closer Islands
-Sp. 1 can increase from low densities in the presence of sp. 2 if the intraspecific competition coefficient (experienced by. sp. 2 from sp. 2) is greater than the interspecific competition coefficient (experienced by sp. 1 from sp. 2) -vise versa for sp. 2 increasing from low denisty -Coexistence: each sp. must have a greater negative effect on its own growth rate than of its competitor: intraspecific>interspecific
Coexistence and Competition coefficients (See written notes)
-unidirectional positive interaction btw 2 sp -normally density-dependant interaction strength -species co-existance -association btw 2 organisms where one benefits, other not affected
Commensalism
-nest in live trees (with heartrot) = cavity nesters -sap leaking from drilled holes is food for other species too
Commensalism: Yellow-bellied sap sucker
-Account for a very high proportion of the total number of individuals in taxonomic assemblages and, to a lesser degree, of the total number of area or locality occurrences -contribute a disproportionally large number of individuals and biomass to assemblages -few species accounting for most biomass
Common Species
-indirect effect of predator on food web -Antagonistic effect of predationb benefits primary producers (predator eats herbivore, plant production increases)
Common predator-regulated trophic cascade
-extent to which common species shape assemblage remains unkown -species richness: dominant influence is a consequence of the shape of frequency distribution of species richness among sites, and species-occupancy tends to be markedly right skewed
Common species and Effects on Assemblage
-small proportion of individuals are typically covered, this will be insufficient to maintain common status -landscape matrix: try to protect a bunch of patches?
Common species conservation: protected areas?
-might not have the same biological characteristics -smaller, shorter generation time = greater propensity for boom/bust dynamic -may see changes in ecosystem service they provide (grassland is not a forest, jellyfish dominated oceans to not provide quality prey-fish)
Common species decline: replacement by others
-DECLINE IN COMMON SPECIES IS ACCOMPANIED BY DECLINE IN OVERALL ABUNDANCE ASSEMBLAGE -but because of large number of individuals, they receive less attention -relative small proportional reduction in their abundance can remove large numbers from assemblage and can impact large areas -commonness itself is rare
Common species declines: systematic patterns
-common species -show major decline in population in past 30 years -down by around 50%
Common species examples: house sparrow, starling
-abundant, widespread -common species are rare -majority of species occur in low abundance (rare), and are narrowly distributed
Common species vs regular species
-frequently regarded as being low risk of extinction because they exist in large numbers -conservation status often overlooked -BUT: they shape ecosystems, contribute to ecosystem functioning, can show rapid population declines -conservation should look more closely at how the trade-off btw species extinctions and the depletion of populations -need to have conservation focus on the role of the species identity rather than simply species richness
Common species: Conservation
-provide larger part of biologically generated physical structure of ecosystem -within taxonomic assemblages: 25% of most abundant species contribute at least 50% of biomass
Common species: Ecosystem structure
-common species shape their environments and are involved in large numbers of biotic interactions (herbivory, predation, parasitism) -exploited by larger numbers of species of natural enemies -common species face fewer individuals of their natural enemies
Common species: Food-web structure
-local abundance and regional occupancy are positively correlated with taxonomic assemblage -common in abundance = common in distribution -species can be locally abundant, but narrowly distributed (thickseed) or locally scarce but widely distributed (great white shark)
Commoness and distribution
-Deborak Rabinowitz -based on: 1. Geographic range: extensive vs restricted 2. Habitat tolerance: broad vs narrow 3. Local population size: large vs small -use this system to come up with 8 possible combos: 7 = rarity, 1 = abunance
Commonness and rarity: Classification
-Resistance: doesnt change much in response to environental disturbance -Resilience: returns to previous state after disturbance -more diverse food webs are more stable -sp influenced by many weak interactions have more stable interactions than species with few strong interaction
Communities are stable if?
-initial of species subsequently affects development of a community: which sp arrives first is important -traits of initial sp can play large role in determining future community (divergence)
Communities: Priority Effects
-Study of patterns in diversity, abundance and composition of species in communities and the processes that underlie them
Community Ecology
High -more total elk killed,diminished elk density -large decrease of calf recruit ~50% -more aspen recruitment, less aspen browsing, less willow browsing, much higher willow production -increased songbird density, and abundance
Comparison in Banff: High wolf density vs low wolf density
-higher number of seeds = smaller seeds -disperal vs fecundity: further dispersal, but not as good competitors? -can only compare sp of similar ecology -trade off btw seed size and seed number
Competition-colonization trade off: seed size vs abundance
-If the competition coefficient (effect of competition on species 1 by species 2) does not equal the competition coefficient ( effect of competition on species 2 by species 1), then competitive asymmetry exists. -if the competition coefficient (alpha12 or alpha21) is greater than 1, then intraspecific competition is of greater importance than interspecific competition
Competitive Asymmetry
-extirpating of a less competitive species by a dominant competive species -two species competing for the same resource cannot coexist at constant population values, if other ecological factors remain constant
Competitive Exclusion
-Host provides a commodity to mutualist and to non mutualist (exploiter of host) -Competitive asymmetry affects allocation of commodity from host -Persistence of obligate mutualism: depends on strength of mutualistic trait of host and mutualist (stronger = better) -ratio of competitive effects btw mutualist and non mutualist affect stable coexistence of mutualism and exploiter -Model shows: EVOLUTION OF A MUTUALISM IN ABSENCE OF AN EXPLOITER MAKES IT VULNERABLE (future kimakeze invasion) -in presence of exploiter: mutualism evolves towards stable state
Competitors + Obligate mutualisms: Ferriere et al 2007
-Genetic diversity -species diversity -ecosystem diversity
Components of biodiversity
-play it safe -organism always uses exactly the same, low risk strategy
Conservative bethedging
-distinguish btw depletion and natural abundance fluctuations, especially when detecting small declines
Conserving common species: Key issues
-Resource is consumed by an individual so not available for others -Most common!
Consumptive Competition
-Density dependent interaction -unstable dynamic
Contramensalism
-priority effect persists as taxonomic dissimilarity across years at sp level -convergence of functional traits (declining dissimilarity) occurs during taxonomic divergence -evidence for biotic drivers of community assebly (inhibition + facilitation) -sp compostitin doesnt change much, but function traits become more similar
Contrasting priority effects on communities
Course grained -coloration changes in mouse sp due to owl predation -same sp, different locations, different generations? Fine grained -migrating arctic charr -experience different spatial environment in their lifetime
Course grained vs fine grained examples
-chatalamus upper limit set by desiccation, lower limit by balanus -remove balanus and cthalamus grows in lower tide -remove cthalamus and balanus does not invade -balanus upper limit set by dessication, lower limit by starfish predation: remove starfish and balanus invades lower tide
Cthalamus (small barnacles) + balanus (large barnacles)
-See written notes
Descriptive Competition Models: LV
-Primary factors: relate to climate and physical environment (temp, moisture, variability) -Secondary factors: build as processes interact in complex ways [diversity begets diversity], complexity is good for biodiversity
Determinants of biodiversity (primary and secondary factors?)
-animal dormancy -delay in development in response to regularly and recurring periods of adverse environmental conditions -escape from harsh coniditons -temporal -example of conservative bet hedging
Diapause (temporal)
-rock snot -native to north america, but has spread to many parts of the continent it hasnt been before
Didymo
-dont put all eggs in one basket -where an individual invests in several strategies at once, wiht low variation in total success as a result
Diversified bet-hedging
-Simpsons index: measures dominance, sensitive to abundant species -Shannons index: measures uncertainty, sensitve to rare species -Pielous index: measures equitability
Diversity indices
-requires variation across landscape of community (spatial or temporal) ?
Does R* promote multiple sp coexistence?
-dispersion -local pops often do not persist for very long -recuperative power of locality and dispersiveness: new colonies are being founded and old ones can be revived + leave harsh conditions (persistence)
Dynamic of Commonness: Metapopulations
-COMMON SP RATHER THAN RARE ARE PRINCIPAL DRIVERS OF SPATIAL VARIATION OF SP RICHNESS -(widely distributed + high dispersal rate) -rare species are more extinction prone: once locally extinct, take longer to re-immigrate than common sp
Dynamic of commoness: Spatial variability
-Bet-hedging: how individuals should optimize their fitness in a variable and unpredictable environment. An individual has to lower its variance in fitness between years in order to maximize its long term fitness (generalist vs specialist)
Dynamics of Commonness: Temporal
-energetic mutualism -nutritional mutualism -protective mutualism -transport mutualism
Dynamics of Mutualisms (4)
-different individuals of a genotype in a population experience different environments -not risk spreading in the sense discussed here: no trade off btw mean and variance in fitness for this sort of behaviour -ex) female insect spreads eggs among plants to avoid chance catastrophese that might destroy individual plants independently
Dynamics of commonness: Within generation risk spreading
1. Initial floristic competition (F. Egler) 2. Facilitation model, inhibition model, tolerance model (Connell and slayter) see written notes: Mechanisms of succession
Early pioneering sp hypothesis
-species multiply and fill the earth, but communities wont grow without limit -assume a fixed, infinite community size -number of individuals increases linearly with area -community assembled in a zero-sum game: total number of individuals unchanged because birth and death rates are balanced -species succeed only if some other species perish
Earth is neutral and crowded: neutral theory and community growth
-environmental patterns -latitude, longitude, depth -temperature, precipitation, salinity -common species widespread, therefore occur across environmental gradients
Ecogeographic patterns
-Common species: structure (breadth of spatial scale), pattern of species richness, patterns of spatial variation in environmental conditions, spatial turnover in species composition -stronger intraspecific patterns on widespread species, they experience greater environmental variation and local adaptations
Ecological Consequences of commonness: Macroecological patterns
-predictable change in species over time -new sets of species modifies environment to enable the establishment of other species -disturbances and predation mediate resource availability, affecting species interactions and coexistance
Ecological Succession
-Genes -Species -Population -Community -Ecosystem (environment + communities + energy flow + nutrient flow)
Ecological Units
-suppression/replacement of native sp -extirpation -loss of biodiversity
Ecological effects
-% of energy transferred to higher trophic level (5-15) -explains limited length of food chains -dependent upon strength of predator-prey interactions as effected by prey detectability, handling + assimilation efficiency
Ecological efficiency
Convergence -clements -proceed towards 1 climatic climax regardless of historical conditions -orderly linear progression -deterministic Divergence -Gleason -mosaic of habitats = mosaic of climax communities -stochastic forces = variation in sequence and timng of sp -even undergo identical environmental conditions, regional sp pool -historically contigent
Ecological succession: Historical theories
-Sere: sequence of change -seral stage: each stage in the sequence
Ecological succession: Sequence of change Vocabulary!
-tradeoff btw rapid colonization rates and low mortality -faster colonizer and lowest mortality = invasive sp
Ecological tradeoffs in multi-species succession
-ecological traits shape abundance and distribution -rare and common sp cannot be readily distinguished by ecological charactersitics
Ecological traits and species differences
-ponds with active beavers show open water ~11 days earlier -access to food sources -protection from land predators -birds nest, lay eggs earlier = breeding advantage -Increases O2 levels = fish benefit
Ecosystem Engineer: Beaver
keystones, ecosystem engineers, foundation species etc
Ecosystem diversity: Key species
-succession, disturbance, colonization
Ecosystem diversity: Processes
-modifying -maintaining -creating habitat -autogenic and allogenic
Ecosystem structure: Significant ecosystem engineers
-rescue effect: if populations on islands eventually go extinct, then island populations can be sustained by recolonization. Thus closer islands receive more immigrants per unit time than islands farther from the mainland.
Effect of distance from mainland
-limits pop size -affects patterns of spatial dispersion -influences patterns of diversity -acts as selective force on traits -limits ability to compete for other resources (tradeoffs) -shrinks realized niche
Effects of competition?
-Pop size: larger areas support more individuals, population less likely to go extinct -Heterogeneity: larger areas contain more diverse environments -these two not mutually exclusive
Effects of island size: species-area relationship
-transport of firewood banned in certain parts of quebec + ontario to curb spread
Emerald ash borer
-when organisms interfere directly with each otehrs access to specific resources -time/E loss, theft of food, injury, death -Both exploitative and interference
Encounter Competition
-local population of species with different body size should have similar energy use, -decline in population density with increase of body size -amount of energy each species uses per unit area of its habitat is independent of body mass
Energetic Equivalence Hypothesis
-transfer of energy btw two species -trophic mutualisms -Carbon = energy Ex) miccorrhizal symbiosis -common throughout boreal region, obligate in pines -pants get improved nutrient uptake (P, N), water relations (nutritional) -Fungus get carbs from root (energetic)
Energetic mutualism
-fine-grained environment: individual experiences environmental heterogeneity within its lifetime = intra-generational -course grained environment: individual remains in single environment throughout lifetime, but varies between demes occupying different spatial locations or across generations (inter-generational)
Environmental Grain
-more heterogeneous an environment is = more niches available = more sp present
Environmental heterogeneity/niche breadth
-all individuals with an equal probability of colonizing open space -colonizer of a site vacated by death/disturbance is a random draw from sp present -probability of being equal to a species relative abundance
Equal colonization ability Assumption
Ecological Equivalence
Equality of fitness of individuals over different environmental conditions at various spatiotemporal scales
-one of the 100 worst alien invasive species in the world -preys on mussels, clams and other crabs -threatens shellfish stocks on atlantic coast
European Green Crab
-Hypothesized evolution: antagonism to commensalism to facultative mutualism to obligative mutualism to cheaters -consequence of underlying conflict of interest in mutualisms - Pellmyr et all 1996: sp derived from yucca moths reproduce without pollinating yucca plants
Evolution of cheater species
-under identical growing conditions, sp will produce more biomass in an area where it has been introduced vs in its native range -invasives exhibit lower herbivore defense rates in introduced range than in native range -sp is not as fit (in its native habitat) at the time of introduction vs when it becomes invasive
Evolution of increased competitive ability hypothesis: plants
-show selective abortion of flowers with heavy moth egg loads -eggs often oviposited by scarring of plant ovaries -evidence: significant negative effect of moth egg number on probability of flower retention -scars = flowers that didnt develop, plants response to cheator -selective fruit maturation with low-egg and high-pollen loads increases seed potential and selects against highly parasitic poor pollinators -maintains stability by checking growth of exploitative mutualist and selecting for high-quality pollination.
Evolutionary Stability of Mutualism: Pellmyr and Huth 1994
-Predatory mite more efficient in simple habitat (larger a) -Predatory mite less efficient in complex habitat -Complex habitat: time lags btw pop cycles of spider mites and predatory mites
Example: Varying predator effeciency (Mites)
Tropical grassland, temperate forest, boreal forest, korean pine forest, tropical rain forestm semi-desertic system
Examples of ecosystem diversity
-Contramensalism (predation, herbivory, parasitism, parasitoidism): species 1 benefits, species 2 is harmed -Ammensalism: species 1 neutral, species 2 harmed. antibiosis/allelopathy (penicillium vs bacteria) -Competition: both species are harmed
Exploitation
Predator -usually larger, lower reproductive rate Prey -generally entirely consumed -density-dependent interaction, ex) presence of predator can decrease prey density -unstable dynamic -many types of interactions
Exploitation: Contramensalism (predation)
-Interspecific competition -One species reduces (or use more efficiently) a resource than other species
Exploitative Competition
-One species reduces (or uses more efficiently) a resource more than other species
Exploitative Competition
-Commensalism: species 1 benefits, species 2 neutral. Normally density-depenedent interaction strength Mutualism -both species benefit
Facilitation
-any pairwise interaction which at least 1 species benefits -interaction: presence of 1 sp alters environment in a way that enhances growth/survival/reproduction of a second neighbouring sp
Facilitation
-modifies ecosytstem to benefit themselves, also benefits other species
Facilitation: Ecosystem Engineer
Commensalism, mutualism
Facilitation: What interactions included?
1. how readily it invades a newly formed or disturbed habitat 2. Its response to environment over course of succession
Factors determining species presence in a sere
-tidal cycle sets up a gradient along rocky shoreline: lower rocks covered by tide for longer than upper rocks
Factors that influence competition: Spatial heterogeneity (rocky shoreline)
-changes in a habitat over time may shift the competitive advantage from one competitor to another -seasonal changes in temp or precipitation patterns can favor different sp -changes in habitat due to successional stage can alter competitive relationships
Factors that influence competition: Temporal heterogeneity
-Inefficient predators: allow prey to survive, more living prey better supports more predators -Outside factors: higher s for predators, lower b for prey -Alternative food sources for predator -Refuges from predation at low prey densities: prevents prey pop from becoming too low -Rapid numeric response of predators to changes in prey pop
Factors that promote stability in predator-prey relationships
-commercial harvest -Money management
Financial effects
Trophic mismatch
Fitness of predator depends on temporal, spatial synchrony with the production of its prey -When there is no synchrony, this is called?
-pop highs and lows do not coincide closely among 4 sp. -sensitive to diff environmental changes governed by different factors, maybe sensitive to different diseases -all in same habitat though
Fluctuations: Moth pops
-sensitivity to environmental change and response time of pop -Sheep: large, greater capacity for homeostasis, better to resist physical changes, long life, generation overlap -Algae, diatoms: short life, rapid turnover, high mortality, pop size depends on continued reproduction, which is sensitivity to food availability, predation, physical conditions. -phytoplankton pops intrinsically stable
Fluctuations: causes
interlocking pattern of independent food chains
Food Web
-provide quantitative framework to link community structure with fluxes of energy and material: link community-ecosystem ecology -reconcile biodiversity with ecosystem function
Food Webs
-Oil sands cause singificant changes in food web structure even when "reclaimed" -changes cause alteration in connectance, linkage, food web stability -strong effects still in 20 yr old sites
Food Webs and Disturbance: Oil sands wetlands
-measure of food web complexity -Max connectance = max possible links excluding cannibalism (Cmax = (S(S-1))/2) -Connectance: Number of links (L)/Cmax -S = Species -Highest level of connectance = 1
Food Webs: Connectance
-number of links per sp tends to be constant regardless of # of sp. -stable environments have more links per sp than unstable -webs in variable environments tend to be less connected -inverse relationship btw connectance and interaction strength (sp in more variable environments interact more strongly)
Food Webs: Connectance (# links per sp)
-various indices to measure strength -Not all species and interactions are equally important: higher frequency of weaker links -relevance: conservation
Food Webs: Interaction strength
-Undirected link: line connecting predator and prey, binary (all or none) interaction -Directed link: vector connecting two sp -arrows represent energy flow (most common) or top-down predatory effect
Food Webs: Linkage
-within chain omnivory: species feeding on consecutive trophic levels in a food chain -different chain omnivory: sp feeding on >1 trophic level spread across different component chains of a food web -ONTOGENETIC/Life-history omnivory: species shifts diet during its life history
Food Webs: Omnivory
Nodes -species/guild Links -show who eats who -arrows describe net effect of each sp on the other -omnivory, intraguild predation/cannibalism
Food Webs: Trophic levels, what consitutes a food web?
-primary consumers: eat autotrophs -secondary consumers -tertiary consumers -decomposers -1 to 1 interactions along a defined heirarchy, 1 organism at each trophic level
Food chains
-degree of clustering of linkages within a food web (sub webs)
Food webs: Compartmentation
-shortest path, minimum number of links connecting two species -if they are connected, they belong to same guild -IF THEY ARE NOT CONNECTED, THEY BELONG TO DIFFERENT GUILDS
Food webs: Distance
-arragement involving recycling of E and materials from top predator to basal sp
Food webs: Reciprocal feeding relationships**
-average feeding links (L) per species as function of connectance and number of sp. - L/S -Each upper node in a food web is defined by its # of prey items (linkages) -monophage, oligophage, polyphage (1, 2, >3)
Food webs: linkage density
but since the 2nd midterm is not cumulative, from here we will go on to lecture 6.
For the final, you will need to include lecture 5. Midterm 2 start study.
-smaller species become larger, and larger species become smaller on islands -uniformity of size on islands
Fosters Rule
-f(V)=aV (consumption rate= attack rate of predator x prey pop size) -Key assumption in early L-V model -Comsumption rate increases in direct proportion to prey abundance -Predator consumes constant fraction of prey regardless of prey density -Consumption rate per predator is linear -Not realistic at large prey densities -Best validated at low prey densities lacking refuge.
Functional Response Type 1
-Consumption rate per predator levels off -Works best with predators that forage for a single prey (specialists) -Limited by prey density at beginning, but then limited by predators handling time after round-off
Functional Response Type 2
-Slow consumption rate at low prey densities: Poor detection of prey -Consumption rate peaks at intermediate prey density = predator satiated -Functional response is non-linear sigmoidal predation response -Works best with predators that switch prey (generalists) or that adjust foraging effort ex) wasps switch prey, spider switch functional response when thatch is added
Functional Response Type 3
-Full range of abiotic and biotic conditions and resources for a species to survive and reproduce
Fundamental Niche
-members all belong to the same species but have a different genetic pool -ex) guppies
Genetic diversity
-exponential -short generation time -all required resources in excess -Pop increase unlimited -Curvilinear increase with time
Geometric Population Growth
ugh come back to this
Glacer bay: Mechanisms driving succession
-each sp with individual range -associations of plants or a community = by product of individual sp seeking out best habitat -asociations/communities change as conditions change
Gleason et al: Individualistic school
-animals living in the south are more heavily pigmented than animals in the north -pupulation of edothermic animals in warm and humid are more heavily pigmented
Glogers rule
aka grazing food webs -based on primary producers -begins with plants -E moves upwards through consumers -<1% energy moves through
Green food webs
-Competition is most intense in resource rich environments -strong competitors: good competitors for light AND nutrients -Resource poor environment (stressed): competition is less important because not all space is occupied -Plant strategies: competitor, stress tolerator, ruderal
Grime Summary
-Organisms have strategies: colonizing ability, growth rates, survival, ability to tolerate stress, ability to live in low nutrient environments
Grime's Model of Competition for Resources
-eats leaves of about 300 plants: widespread damage
Gypsy moth
-Larger prey need more handling time -lower w (max feeding rate) and asymptote is also lowered
Handling Time
-spatial and temporal -bottom up forces set trophic template for all food webs and interactions therein -heterogeneity at each trophic level buffers against strong cascading effects
Heterogeneity and top-down/bottom up factors
-Alternating top-down (cascading) effects of a top predator on a species at lower trophic levels within a food chain
Higher-Order Species Interactions: Indirect Effects
-if you eliminate one and replace it = no biodiversity loss -if you have loss of more than one native species, homoginization increases = biodiversity decreases -more species change due to introduction of non indigenous fishes than to loss of native fishes -this pattern may not be general, may vary from system to system
Homogenization of Flora and Fauna
-lower levels reproduce quicker -things on lower levels are very energetic, can sustain larger organisms
How are inverted biomass pyramids sustainable?
S(t +1) - St = speciation + dispersal - extinction (stochastic/drift or deterministic/selection)
How can a species pool change over time?
-adaptive trade-offs (no species is best at everything) -niche differences are a mechanism that maintains biodiversity by allowing species to coexist -interactions such as competition etc are viewed through the lens of niche theory
How do niches promote coexistance (niche theory)
-Competition: reduces species dominance -Predation: reduces competitive exclusion -Mutualisms: enhance ecosystem processes
How do species interactions promote biodiversity?
-Grow species in absence of competitors -experimental data -resource level where growth rate = 0
How do you determine R*?
Competitive exclusion results in resource partitioning. This creates niche differentiation of realized niche. This reduces competition and increases species diversity. Competing species more likely to coexist when they use resources in different ways.
How does niche differentiation occur and what are the results?
-species abundance distribution -fits to the empirical data on the species abundance distribution of Tropical Trees -however, other models can also succeed in predicting observed data (like niche differentiation focussed ones)
How to test neutral theory?-
Characteristics defined only at the community level -number of species -relative abundance of those species - type (some functional characteristic of ecological importance, like a guild) of species -number, types, strengths of interactions among species (ie structure of food web)
How would you measure the structure of a community?
-came up with neutral theory -worked in the tropical rainforest -evolution and maintenance of high sp diversity in tropical we forest is a puzzle: how do 300+ sp of tree occupy 300 diff niches? -hubbell took another approach than looking at niche specialization
Hubbel (2001)
