Ecology Final: Ch 15, 16, 17, 18

Strong Interactions: Focusing on Community Structure

Keystone species: Species that have significant influence on community structure disproportionate to their biomass. e.g. sea otter and kelp communities

Landscape Ecology

Landscape structure and elements -Metapopulations and patchiness Fragmentation -How much do you need? Edges and Corridors -Connection between habitat patches

The Global Carbon Cycle

Largest natural exchanges of CO2: Ocean/Atmosphere & Organisms/Atmosphere. These are roughly in balance. Current carbon cycle is not in balance. Why? Global Warming

Landscape: Community Example

An area containing several different communities. -Example: The climax boreal communities --Muskegs --Bruce Spruce --Subalpine --Alpine

Community

An assemblage of species

Mutualism

+/+ interaction: both participants receive benefits Happier, no fitness costs

Common effects of Fragmentation

-A new habitat is created around the edge of forest fragments --Intermediate disturbance hypothesis: creates new habitat -New, possibly exotic species may invade forest fragments --Exotic invasive species do well in edges (rapidly changed areas); woodpeckers are edge species; hawks like fields to find mice; phenotypic plasticity -The disturbance regime in forest fragments is different compared with continuous forest. -Animals and soil organisms necessary for pollination, seed dispersal or nutrient cycling of particular plants may vanish from forest fragments. -Decreasing area of forest fragments brings forth increasing risk of extinction of local populations within them. (is there a corridor for species to find a new forest)

Climax

-The ultimate stable association of plants and animals -All something that cannot be out competed by something else -Equilibrium -Often referred to as 'primary' or 'mature' communities (Oak trees have allelopathic properties to make soil uninhabitable for other species) The climax for a site is dependent on the topography, climate, disturbance, etc. characteristic of that site. -all biomes do not have the same climax community (creosote flats)

Causes of Structure in Landscapes

1. Activities of Organisms -Humans: 6 Ohio landscapes & Ohio valley --remnant patches: original landscape --introduced patches: human altered Precolonial North America: Beavers landscape engineers 2. Fire and other natural disturbances --Example: Praire and Big Woods edge in midwest --Example: Chaparral and live oak interdigitation in California 3. Geological and Geomorphological Processes Eg mountain landscapes patterns differ from pains landscape patterns -Can be very subtle: -Difference in aspect (e.g. southern v. northern exposure) -Difference in slope 4. Climate Affects the biome (large-scale community) Interacts with geology --Mountainous areas have different climates due to changes in altitude and aspect --Geology determines land forms such as rivers --But how often river floods and creates patterns of floodplain communities depends on climate

Some generalizations about food webs

1. Cycles are rare in food webs (esp. if time lag) -Complexity of interactions dampens individual interactions, creating stabilized relationships 2. Average proportion of predators (or consumers generally) increases with regard to basal species as the diversity of the community increases -Diverse communities tend to be top heavy (top level predators) (Community with a lot of different species can support more predators) 3. Contrary to intuition, food-chain lengths do not differ greatly among ecosystems with different primary productivities. 4. There are only slight differences in chain lengths where consumers are vertebrates, compared with where they are all invertebrates (coral reef lots of chain links) 5. Chain length is smaller on smaller islands. In general, smaller areas support fewer tertiary predators. 6. Chains are shorter in areas with frequent natural or experimental disturbances. (ASU west highly disturbed) 7. Chains are shorter in two-dimensional habitats such as grasslands than three-dimensional habitats such as forests or reefs. (Chad likes this)

Major hypotheses (arrayed equilibrium BU to non-equilibrium TD)

1. Microenvironmental niches (bottom up - most stable) 2. Intermediate disturbance 3. Lottery (top down)

Each landscape has a landscape structure or matrix defined by:

1. Patch size 2. Patch shape 3. Patch composition 4. Patch number 5. Patch position

Three ways to study food webs:

1. Source webs (top down) focus on 18, 17, 6 -All of the species that eat species A, all of the species that eat those, etc... 2. Sink webs (bottom up), focus on 3 (i.e. wolves), 10,12 -All of the species that are eaten by species A, all of the species that they eat, etc. 3. Community Webs

Example: Psychotria on Barro Colorado Island (S. Joseph Wright)

18 species coexist on island in Panama Canal Each is found predictably within a particular microhabitat Very little overlap Specific niches - pure bottom up - great example Also, Darwin's finches, adaptive radiation based on seed size and bill morphology

Tree diversity

50 ha plot in Yasuni National Park, Peru, had more than 1300 species of tree. Why this variation in diversity? North America north of Mexico has a few more than 700 species of tree.

Community Webs

A more accurate account of trophic webs would take into account ALL pairwise interactions, including competition and mututalism. Can get a sense of the strength of the web by looking at COMMUNITY WEB CONNECTANCE

Landscape

A mosaic of ecosystems and their contained populations and communities. The study of relationships between spatial pattern and ecological process over a range of scales. Important point: scale can vary drastically!! Example: The Valley of the Sun -Glendale: Suburban -Buckeye: Desert/Suburban/Agriculture -Phoenix: Urban -Salt or Hassayampa River: Riparian -Usery Mountains: Desert Mountains

Insect diversity

A single tree: -Terry Erwin collected 1500-2500 species of insect FROM EACH INDIVIDUAL TREE in this tropical rainforest national park! 85% new to science. Why this variation in diversity? -About the same # of insect species as are known from Arizona

Mutualism Review

A wide array of interactions, many of them critical to the functioning of complex communities and ecosystems, are mutualistic. Models suggest that weakening of interaction stabilizes mutualism. However, we observe many highly dual obligate mutualisms. Suggests assumptions of the model are often too simple. Considering evolution suggests what may happen with instability. Comparative analysis allows testing of ecological predictions.

Why are edge effects problematic?

After all, provides a preferred habitat for some organisms. -Deer, Ruffed grouse Because animals from the adjoining communities also present, diversity can be very high HIREC - human induced rapid environmental change However... Most organisms from forest interiors cannot survive the low humidity, high light environment of edges. Many animals from forest interior will not remain in edge habitat. Edge functions as buffer zone for interior, but is not interior itself. Humidity, temperature, susceptibility to wind, etc. all very different. more clear cutting = more wind susceptible

Example: A return to ants and butterflies

About 1/2 of butterflies in the Lycaenidae associate with ants. About 1/2 of these are mutualistic with their ants. The other 1/2 are parasitic: they either eat the ant larvae, are fed by ants, or secrete sugar-water (fake gift).

Species interactions are complex

Accurate community web would include all pairwise interactions, the strength of those interactions, the indirect effects of those interactions, as well as the effects of density-dependent and density-independent population regulation mechanisms. Would have to solve numerous Lotka-Volterra equations simultaneously to adequately describe community food webs.

Single Large Reserve (*Test)

Advantages: 1. Low edge effect 2. Good for organisms with high area requirement 3. Easy to manage 4. Low local extinction Disadvantages 1. All eggs in one basket 2. Diseases can spread 3. Low environmental heterogeneity 4. Difficult to obtain

Several Small Reserves (*Test)

Advantages: 1. bet hedging 2. diseases unlikely to spread 3. high environmental heterogeneity 4. easier to obtain Disadvantages: 1. high edge effect 2. cannot support species with high area requirement 3. difficult to manage 4. high local extinction

Fragmentation

Anthrogenic (man-made) fragmentation often with 'harder' edges.

Observations

Ants tend caterpillars, provide shelter at night and actively attack parasitoid wasps. Ants gather secretions from specialized glands on caterpillars. Fitness gain: ants nibble gently on caterpillars - drink sweat - possibly leave formic acid behind

Food Webs and Diversity

Before we were looking at species diversity Now we are adding diversity of (1) trophic levels; (2) chains; and (3) links. Rather than ask how many species inhabit a community, we now want to know about the diversity of linkages - how much of the diversity feeds a particular species. Studies of food webs try to make generalizations connecting these different aspects of diversity

Case Study: Chalk grasslands of Southern England

Bunnies are main grazers - bunnies impose constant disturbance below. Set up experiment which excluded bunnies from enclosures and compared diversity Diversity decreased dramatically in excluded areas when bunnies go away Or, disturbance (presence of bunny) increases diversity!! Superior competitors no longer limited by bunnies are released to exclude much diversity that is present when bunnies impose disturbance. Bunnies have a qualitative effect disproportionate to their sheer numbers = keystone

Mutualism and ZGI: Dual obligate relationship

Combine: Even if the isoclines cross, there is instability, but possible coexistence. But, here the strength of the mutualism is less intense. EG: it takes fewer N1 to sustain N2 i.e. more of the graph shows N2 growing and vice versa for sp.2 Open circle, not stable equilibrium

What is the evidence for increased CO2 concentrations?

Ice cores Direct monitoring

Connectance equation

CONNECTANCE = actual # of interspecific interactions/potential # of interspecific interactions This relates to community structure: The higher the value of connectance, the more influence one species has on the community structure. Also, there is more structure anymore opportunity for coevolution (in predator-prey relations, mutualisms, or niche partitioning) The lower the value, the less predictable, less sustainable

Secondary Succession

Changes at a site that previously had a community and then suffered a major perturbation which reset the stage of the community to an earlier point in the succession process but did not reset it to the primary succession stage. -Disturbance not as dramatic -Response not as dramatic -Fires

Succession

Changes in a community at a site following either habitat disturbance or colonization of a new substrate. Plants and soil over time.

Shape parameter S measures how much edge there is vs. minimum

Circle has minimum ratio of perimeter:area -Another way of saying circle has more interior than oval S=P/2*sqrt pi*A S = patch shape parameter P = perimeter A = patch area -Circular shape has S = 1 -Oblong shape has S > 1

Species abundance and diverts and other definitions

Community: association of interacting species inhabiting some defined area Species abundance: the # of individuals present of any given species = # of individuals/m^2 Species diversity: the # of different species present Species richness: # of species in the community - chad this same as species diversity Species evenness: relative abundance of species present - 300 quail, 3000 doves, 1 mockingbird (uneven) Population abundance - one species Density - # of individuals/m^2

Theoretical Treatment of Mutualism: Lotka Volterra

Competition: dN1/dt = rN1((K1-N1-a12N2)/K1) Can use this for the basis of mutualism model. In competition -a12 implies an antagonistic relationship. In mutualism, can use +a12 to imply a mutualistic relationship. Mutualism: dN1/dt = rN1((K1-N1+a12N2)/K1) +a12 becomes the MUTUALISM COEFFICIENT. Need this equation for both species. Mutualism: dN2/dt = rN2((K2-N2+a21N1)/K2)

Review and Introduction to Ecosystem Terminology

Consumers: heterotrophic organisms Require OM and energy from the biotic environment. -Biotic: materials that are, or were once living

Food Chain Link

Consumption of one individual by another

Community Food webs

Diagram of all TROPHIC relationships among the species of a community Note: ignores competitive interactions within trophic levels, e.g. intra-guild predation, cannibalism

NPP

Determines how productive an ecosystem can be. Depends on temperatures, N, P, or H2O. Terrestrial ecosystems: -highly correlated with leaf area index: --Forests: 49% --Grasslands: 9% --Wetlands: 3 % --Agriculture: 6% Note that NPP does not equal species diversity Why not? Recall the realized niche

What is disturbance?

Discrete, punctuated, killing, displacement, or damaging of one or more individuals that directly or indirectly creates an opportunity for new individuals to be established. (Intro of new species, putting out bird food) -A broader definition is helpful. climate change, fire, predation, invasive species, and many other human inventions (e.g. bird feeders) -If you view disturbance broadly (e.g. predation) you can view eq. hyp. as BU and diesq. hyp. as TD -Which determines species diversity in a community - BU or TD forces?

Recently this has been modified: The Biased Lottery

Disequilibrium component: you have to be lucky enough to get there. Equilibrium component: you still have to be able to compete with all of the other seedlings that also go lucky enough to get there. Have to be good to be lucky (skills to deal with drought, parasites, grazers)

Is biodiversity explained by productivity, and niche space alone (BU)?

Disturbance = continuous change Overlay disturbance on theory of niche overlap and competitive exclusion (i.e. microenviron niche hyp) Can disturbance prevent exclusion by allowing considerable niche overlap? Can disturbance maintain diversity at a higher level than competition alone? Disturbance, Predation (biotic), Cannibalism - con specific, Interference comp, Exploitive comp, PP

Strong Interactions: Focusing on Energy Flow

Dominant Species species that have significant influence on community structure by virtue of high biomass (i.e. creosote in desert flat) e.g. Blue spruce in taiga biome

A food web of the insects in the pitcher plant Nepenthes albomarginata

Each line represents a trophic linkage; predators are higher in the figure than prey Need these connections to sustain biodiversity Biodiversity, Sustainability, Niches/Ecosystems, Take the load off each other Now we are looking not just at species diversity, but the diversity of interactions

Landscape Structure

Each of these communities forms a -patch: a relatively homogenous area that differs from its surroundings -Also called landscape elements

Biodiversity and Ecosystem Stability

Ecosystem stability (whether the community is at equilibrium or disequilibrium) may play an important role for determining species richness within a given area. There is evidence for varying levels of the equilibrium and non-equilibrium hypotheses. But a combination of these is probably most prominent.

What are ecosystems?

Ecosystems are energy transforming systems. Ecosystems are nutrient recycling systems. These are controlled by physical, biological and chemical processes.

Energy Flow Through Ecosystems

Energy flows through a system only once. Producers absorb solar energy, convert it to chemical bonds. Energy content passes up food chain; eventually lost as heat, -therefore, requiring continual input. Original inorganic materials are recycled, generally no new input required Need continual input from sun

First Law of Thermodynamics

Energy is neither created nor destroyed, it is only transferred -in any process, the total energy of a closed system remains constant -You can't get something from nothing

How do we explain this variation in diversity?

Equilibrium: point of view that the species and species number in a community (after time) stabilize through interaction ecology (comp, exploit, mutualism...) and coevolution. (good null hypothesis) (bottom up) -emphasize resource availability, niche overlap and interactions -relatively static -leads to stability Disequilibrium: point of view that disturbance and succession cause communities to constantly change in species and species number, never settling to a stable equilibrium (top down) -emphasize constant dynamic change in environment (predation, hurricane) -how we maintain diversity, more realistic

Example: La Selva Biological Station and Braulio Carrillo National Park, Costa Rica

Established in 1954, La Selva Biological Station one of the premier research locations to study tropical ecology. Since that time agricultural communities have been built up all around it. As a result, La Selva was in danger of becoming a premier place to study edge effects in tropical ecosystems. Braulio National Park (46,000 ha of tropical forest) short distance to the south. Large enough to support the most sensitive rainforest interior mammals and birds. Solution, OTS (organization of tropical systems) and Costa Rican government protected a corridor connecting the two, has allowed most sensitive species to persist in La Selva

Primary Succession

Establishment and subsequent changes in a community from newly formed habitats without plants (soils). Before any plant life has established itself. -start from scratch -involves considerable modification of the environment by early colonists (pioneer or 'r-selected' species) -Specialists that thrive in highly disturbed areas. -Volcano (lava flow) -Retreat of glaciers (melted and expose substrates with no plants)

Second Law of Thermodynamics

Every energy transfer or transformation increases the disorder (entropy) of the universe. -In any energy conversion some energy is transferred to the surroundings as heat. -For example, disorder is added to the cheetah's surroundings in the form of heat and the small molecules that are the by-products.

Or maybe not ...

Evolution of parasitism a common result of mutualism. Suggests that mutualism may be unstable. The result of reciprocal exploitation, not altruism. Suggests that mutualism may often be a tug-of-war of interactors

The Lottery Hypothesis Example

Example: rainforest gaps Regeneration occurs mostly in gaps after tree fall If you are lucky enough to have had a seed dispersed to this area, you get established.

Case Study: Experimental manipulation of tidal communities

Exclusion of Pisaster (starfish) results in dominance of Mytilus and loss of biodiversity. Keystone predator adds to biodiversity!! There is often a tradeoff between competitive ability and defensive capabilities. -In other words, its hard for any 1 species to be good at both competing for resources (bottom up route to pop growth) and surviving predation/disturbance (top down route to pop growth) -Therefore an intermediate level of TD control can promote diversity

Trophic Levels

First level: autotrophs. - Primary Producers. (Convert inorganic material and energy into organic matter) Second level: herbivorous heterotrophs. - Primary Consumers. Third level: carnivorous heterotrophs. Prey on herbivores. Secondary consumers. Fourth Level: carnivorous heterotrophs. Prey on carnivores. Tertiary consumers. ie Frog, bat, moth, plant Notice how levels can affect each other directly and indirectly Remember, categories are difficult in reality! Organisms can be at multiple levels (e.g. omnivores) What are praying mantids? -Generalist predators that take: herbivores making them (2 consumers) and carnivores making them (3 consumers) Do quaternary consumers exist? Only rarely (possibly humans) - predators of predators that are predators These are concepts to help us understand how energy flows through an ecosystem. Will be better-represented by food webs. Arrow points in direction of E flow

Food Web Terms

Food chain: a single path UP the food web Tertiary Consumer - predator of the predator <--Secondary Consumer - Coyote <--Primary Consumer - Bunny <--Producers or Decomposers - grass Arrows go up Represents energy transfer - up through the web

Food Web Participants

Food web driven by trapped insects and their decomposers

Is this a mutualism?

For it to be a mutualism, there must be benefits to both the ants and the butterflies (+/+) If there is no benefit to one, it is a commensalism (+/0) If there is a cost to one , it is a parasitism (+/-)

Edge Effects

Forest interior and exterior environments are VERY different physically. Edge effects can extend 50 m - 200 m into a fragment. Therefore, with 10 ha parcels, there is no forest interior. Edge effects effectively decrease the actual size of the fragment.

Fragmentation

Fragmentation is a major result of land conversion. Refers to the process of taking continuous habitat and subdividing it into patches isolated from each other by roads or another habitat type. -Roads are unique corridors -Lots of patches out there, fragmented by humans, fire, earthquakes; beavers can fragment water habitat

Landscape: Population Example

Glanville fritillary butterfly exists as patchy METAPOPULATION

Ecological Efficiency

Gross production efficiency: the percentage of energy consumed by an organism which is available to the next trophic level.

Practical Implications

Habitat fragmentation is an inevitable consequence of human development. How can we minimize its effects and thereby maximize conservation efforts? There are consequences for nature reserve design (needs government regulation)

Connectance

High connectance -> structuralist, bottom-up, equilibrium viewpoint of community structure. Low connectance -> individualistic, top-down, non-equilibrium viewpoint of community structure. 2 hypotheses for pop. growth in invasive species -enemy release (top down) -resource abundance (bottom up) (equilibrium is BU, non-equilibrium is TD)

Types of Mutualism: Ruminants and gut flora/Termites and gut flora

Highly specialized. Long coevolutionary history. Obligate for both Cellulose breaks down wood for termites.

Types of Mutualism: Pollination

Huge variety of specialization. Both obligate and facultative relationships. 'Cheaters' very common. When would we expect cheaters? Getting all the benefits without paying the costs. Flower - produce less nectar - attractive but not beneficial. So perhaps mutualism descends into exploitation when costs are high. Cheater pollinator - only take resources Flower more likely to become cheater. Not surprising then that evolutionary explosion of insects coincided with exposition of flowering plants. Shared trait of pollinating between insects and birds - shared ancestry or convergent evolution.

Why is fragmentation relevant?

Human population growth and subsequent demands on agriculture, natural resource extraction, and infrastructure development are turning the world into fragmented habitats. Need to understand dynamics of fragments if we hope to understand them. -With particular emphasis on how corridors might connect disjoint patches

Primary production

If energy is conserved and some energy is lost to biological systems as heat, ecosystems must have some input of energy. Sunlight This is the fixation of energy by autotrophs in the process of photosynthesis. Usually units are kcal x m^-2 x yr^-1

How do we know where increased CO2 comes from?

Indirect evidence -Annual in atmospheric Co2 well within annual burning of fossil fuels -Dips in fossil fuel burning result in dips in CO2

Six Ohio Landscapes, with various forest patches on non forest background

Monroe, Somerset, Washington Concord, Hudson, Boston Monroe and Concord have small patch sizes. Washington and Boston have the largest patch sizes Boston's large patches have more core and less edge Jaguars need core, shade Edges - mockingbirds and pigeons

Microenvironmental niche hypthoesis

More productive environments have more possible niches. Can therefore have more species (Lots of different resources and niches - lots of species)

The types of mutualism

Mutualism as a listed keyword receives considerably less attention than predation or competition. Partly because of diversity of interactions that are often termed mutualism. Difficult to unite them under similar set of hypotheses. Also diversity of strength and length of relationships.

Review and Introduction to Ecosystems Terminology

Niche: The role of an organism in its community, factors limiting its life, and how it acquires food. Fundamental niche: the full range of environmental conditions (biological and physical) under which an organism can exist. Realized niche: Through pressure from, and interaction with, other organisms (e.g. superior competitors), species are usually forced to occupy a niche that is narrower than fundamental. Niches can be defined on a continuum: -Broad -ecosystems: eg 'consumer, primary producer' -community: eg keystone predator -population: eg meta-population source/sink -individual level: eg keystone individuals -Narrow

Given what you learned from interactions ecology and the stability/coexistence of species, what does an ecosystem need to support a great number of species?

Niches

Does selection act to maximize ecological efficiency?

No reason to believe this - organisms are wasteful - humans waste energy Selection acts on individuals

Types of Mutualism: Legumes and Nitrogen-fixing bacteria

Nodulation specialized morphologically, but not species-specific. Allows legumes to live in Nitrogen-poor environments. Facultative.

Are observations enough?

Not a love fest - nature is full of selfish organisms Mutualism can be thought of as mutual exploitation (marriage) Each participant always wants to get more from the other (maximize benefits) while giving less (minimizing costs) Both get something - positive outcome Therefore, the evolution of parasitism from mutualism is quite common. Researchers must show experimentally that both participants benefit. Caterpillar gains avoidance of wasp eggs parasitizing

Mutualism and ZGI: Dual facultative relationship

Notice - isocline hits on different axis (K) N1 can exist in the absence of N2 - Carrying capacity - Adding mutualism increases the carrying capacity Combine in dual facultative relationship - Possible intermediate zone of coexistence

Obligate vs. Facultative Mutualism

Obligate: necessary for survival of the participant (ants) Facultative: non necessary for the survival of the participant (caterpillar) Individuals can survive without the interaction. But have better fitness if in the interaction. Can be dual obligate, dual facultative, or mixed (obligate for one, facultative for the other). Mixed for the ant caterpillar interaction

Theoretical Treatment of Mutualism: Lotka Volterra

Outcome depends on whether or not relationship is Facultative or Obligate. Facultative: Relationship IS NOT necessary for persistence of population. Obligate: Relationship IS necessary for persistence of population. This can be dual facultative, dual obligate, or mixed.

Experimental manipulation

Pierce (1987) removed and then excluded Iridomyrmex ants using Tanglefoot. Then tracked mortality in treatments with and without ants. Showed mortality much higher in treatments without ants. Here is the benefit to the caterpillars (Top Down Benefit). Larvae do survive without ants just not at a high rate What about costs to ants? Why do ants tend larvae? Facultative mutualism

A comparative approach to the evolution of mutualism

Pierce found that parasites were DERIVED from mutualists in all cases. Additionally, they were always at tips, suggesting that they go extinct after time. (Stunt speciation, terminal evolution, drive one species extinct) Mutualisms often become exploitations. Parasitism through convergent evolution.

Trophic Level

Position in the food chain, determined by the number of energy transfer steps to that level Tertiary consumer <-- Secondary consumer <-- Primary consumer <-- Producers/Decomposers

Intermediate Predators

Primary and Secondary consumers

Review and Introduction to Ecosystem Terminology

Producers: autotrophic photosynthetic organisms These produce organic material (OM) from inorganic chemicals and some source of energy. -Terrestrial: predominantly green plants -Aquatic: predominantly algae

Ecological Efficiency

Production efficiency is high for arthropods (10-25%), low (<5%) for vertebrates. Why? Costs of endothermy Production efficiency is higher for carnivores than herbivores. Why? Constraints on herbivory Net ecological or food chain efficiency: the proportion of productivity in one trophic level which is actually converted into productivity at the next trophic level

Food Webs

Putting some order into communities

Ecological Pyramids

Pyramid of biomass: There is less biomass as one moves up the food chain. -but don't hawks weigh more than caterpillars? There are a few exceptions to this. E.g. algae are outweighed by their herbivores in many aquatic systems.

Primary Succession Examples

Receding glaciers in Alaska. Soils are thin clay deposits. Glacier Bay glaciers have been retreating steadily over the last 150 years, you can examine stages of succession areas uncovered 150 years ago to areas uncovered 1 year ago.

Fragmentation as a natural process

Reflects inherent heterogeneity of natural ecosystems. Maintained by mosaics of environmental features and disturbances. Natural fragmentation often with 'softer' edges (ecotone transitions).

Strong Interactions and Food Web Structure

Removing weak feeding relationships produces a more understandable picture

Beginnings of succession

Requires a reset button Very predictable on what plants will come in and takeover - start is ragweed (R selected) Soil stabilizes - weed and shrubs

Net Primary Productivity

Respiration in which potential energy becomes kinetic energy and work (growth, maintenance, etc.) Some heat is always lost to the system. (2nd law)

Primary Succession: Examples

Sand dunes on Lake Michigan. -Can walk through the serial stages on a line perpendicular to the lake shore, going from young to older and older seral stages. A. sand dunes on shore: vegetation absent B. Perennial grasses: stabilize and add organics C. Annuals: further enrich soil and stabilize ground from erosion (more biodiversity) D. Shrubs E. Pines F. Forest: climax stage. First black oak and then beech and maple

The Intermediate Disturbance Hypothesis

Says that species diversity is highest as intermediate levels of disturbance or predation. Why? 1: Competitive dominants exclude other species (selection favors BU winners) 2: Disturbance or predation so common that only best disturbance and predation-resistant organisms exist (selection favors TD winners) -At intermediate levels nobody can dominate - combo of TD and BU forces maximize niche space by making equilibrium possible

Edge effects, nature reserve design, and corridors

Second result from Minimum Critical Ecosystem Size project: Isolation increases the effect of fragmentation. Example: smaller fragments left standing near to other smaller fragments lost less diversity than isolated smaller fragments. More resources to support populations. IE clusters of small patches can exist as metapopulations, but isolated sinks got no chance Because often resources and external pressures only allow the preservation of small fragments of habitat, is there anything that can be done? Corridors: habitats made largely of edge habitat that connect larger fragments Many animals that will not exist in edge habitat will use edge for dispersal.

Secondary Production

Secondary or consumer productivity: productivity by consumer organisms (heterotrophs). Energy budget of consumer (or population of consumers): E(production)=E(ingested)-E(respiration)-E(feces)-E(urine) E(production) > 0 if organism is to survive and reproduce (what is ingested is not all used)

Structure of Landscapes

Shape may also be important. Oblong patches will have longer perimeters or edges than circular patches. Edges = Ecotones -Some organisms live in ecotones, others need to live in patch interiors. -How do we quantify edginess?

Nepenthes: Pitcher Plants

Simplified communities Tree holes Plant containers

What are ecosystems?

Simply, ecological systems Interacting systems of living organisms and their physical environment Combination of biotic and abiotic Broad definition, essentially the same as our definition of 'ecology'. But ecosystems ecology describes a specific sub discipline of ecology.

The SLOSS debate (*Test)

Single Large OR Several Small Reserves? Example: If a government/individual/conservation organization could afford to conserve 10,000 hectares, is it better to conserve one 10,000 ha plot, or ten 1,000 ha plots? Like Costa Rica - single plot would be best

Landscape ecology

Spatial ecology

The Minimum Critical Ecosystem Size Project: RESULTS

Striking correlation between habitat size and community diversity. Even largest reserves are too small for some species (jaguars, ant pittas). Strongest result: very small ecosystems are VERY bad. -Species need each other, bad for biodiversity, don't have resources to sustain Why? Main reason: smaller fragments do not have the resources to support sustainable populations. Also, edge effects...

Limitations on NPP in different ecosystems

Terrestrial: Evapotranspiration -Temperature and rainfall -How does this relate to the different biomes? --What biomes are most productive? Freshwater ecosystems: Phosphorus Marine ecosystems: Nitrogen (eutrophication) -but recall that nutrient balance is critical -too much N and P can be devastating

Food Web Participants Top Predators

Tertiary consumers black widow

Example: The ocelot in south Texas

Texas wildlife department in the midst of a 20 year project to create corridor habitats between pockets of South Texas and scrubland. biologists used knowledge of ocelots tendency to wander through roadside scrub (as evidenced by the fact that 20% of all known ocelots in Texas were killed by vehicles in a 5-year period) to predict that protected corridors could save the south Texas populations. As a result of considering the landscape ecology of southern Texas and the biology of the ocelot, the population has increased and stabilized at about 120 individuals. Consider urban Phx coyote use of paseos

Why do we care so much about Carbon?

The Greenhouse Effect -This is why there is life on earth -Not only man made global warming machine Traps gases and makes atmosphere livable - traps everything Releases unnatural amounts of carbon CO2 - 0.03% - not most abundant but most produced by us

Example: Jalmenus butterflies and Iridomyrmex ants

The Imperial Blue butterfly from eastern Australia are tended by ants in the genus Iridomyrmex. Ants guard the caterpillars and escort them into and out of their nests at dust and dawn.

Suess Effect

The burning of fossil rules has a profound influence on C reservoirs. (Burn old dead carbon) These fuels, obtained from the Earth's crust, are so ancient that they contain no C-14 at all (5730 yr half life). When the fuels are burned, their C is released into the atmosphere as carbon dioxide. The annual release of this 'dead' carbon amounts to approximately 5,000,000,000,000,000 kg as compared to the 7.5 kg of C-14 produced annually by cosmic radiation in the upper atmosphere. There is a well-documented decrease in atmospheric C14 Less C14 is being incorporated into wood Implicates human behavior as reason for global climate change. Human consumption fossil fuel burning is leading to climate change.

Net Primary Productivity

The energy available to the ecosystem. NPP = GPP - Respiration

The Greenhouse Effect

The greenhouse effect maintains the temperature of the earth in a reasonable range. Increasing the amounts of greenhouse gasses in the atmosphere increases the amount of heat radiated back to the earth. Decreasing the amounts, decreases the amount of heat

Lotka Volterra Mutualism

The less intense the relationship, the more likely coexistence. This is difficult to match with reality - there are many instances of obligate, highly inter-dependent mutualizes. Violation of assumptions of model all too common. -Density-dependence in obligate relationships. -Evolutionary responses very important.

The Lottery Hypothesis

The most non-equilibrium (about chance) Community assemblage is based on contingency You get lucky to get the right circumstances for successful establishment -Kind of a null hypothesis (like hardy weinberg)

Trophic level

The order in which organisms 'receive' energy.

Sere (stages)

The organisms in a community at a given point in sequence. The final sere is the climax. Volcano -> no life -> minimal life -> trees

Gross Primary Productivity (GPP)

The total amount of energy fixed by all the autotrophs. Is all of this energy available to the ecosystem?

Pyramid of numbers

There are fewer individuals as one moves up the food chain. There are numerous exceptions to this.

The SLOSS debate

This is an ongoing question is reasonably complex. Minimum Critical Ecosystem size project set up in Brazil through cooperation with government, researchers, and timber companies. Conserve everything from 10 ha to 10,000 ha and examine effects on ecosystem and community dynamics

Pyramid of Energy

This is the most useful pyramid. There are NO exceptions. There is always more E available in lower trophic levels. Why? Thermodynamics: -1st law: energy is neither created nor destroyed, it is only transformed -2nd law: In any energy conversion some energy is transferred to the surroundings as heat.

Low diversity community with lower ratio of predators:prey than high diversity community

This means that SPECIALIZATION increases as species diversity increases! (the more species you can get, the more specialization)

Consequences of Fragmentation

Total patch size decreases Physical continuity of patches decreases Edge: Interior ratio increases -Re: 'S' parameter increases Habitat isolation increases Habitat loss increases

Species contributing to 'High Connectance': Strong Interactions

Two potential ways to represent: 1. Abundance: food web including those species representing a high proportion of the biomass at each trophic level. Emphasis is on energy flow through food web. 2. Strength of Interaction: Food web including those interactions that have a dominant influence on community structure. Emphasis is on degree of influence of interaction on community structure

Experimental Manipulation: Exclusion Experiments

Unable to examine effects of caterpillar removal because ants abandon trees without caterpillars (obligate association from the ant's perspective: asymmetry!). Looked at ants going up tree (dotted line) vs those going down (solid line). Ants going down had food rewards from caterpillars. Gains in weight translate to an estimated 100 new worker ants per day per 62 caterpillars tended. Here is the benefit to ants (Bottom Up benefit) Obligate mutualism relationship Material benefits - licking nutrients from partner

Ecosystems and Energy Budgets

Understanding how energy flows through an ecosystem is essential in understanding the productivity (amt of energy), species diversity, and trophic level diversity there is in any given community.

Landscape Ecology

Understanding that ecosystems exist in a mosaic allows us to more accurately address questions concerning community structure and population structure. Combining knowledge of landscape ecology and species biology allows us to make informed decisions on conservation issues and nature reserve design.

Types of Mutualism: Protection

Usually more specialized. Often asymmetric - one is facultative, one is obligate

Types of Mutualism: Fruit Dispersal

Usually very generalized So facultative its often difficult to tell if its a mutualism. Ex: squirrels and nuts

Types of Mutualism: Cleaning

Very generalized. Prone to cheating. Facultative. Birds cleaning bugs out of bulls nose. Fish eats parasites out of other fish's eyes

Examples:

Warwickshire, UK: Industrial - Island of Industry Sumatra, Indonesia: good coffee Neotropical rainforests: lumber, hub of species diversity Phoenix is a disturbed ecosystem

Biodiversity

We use this framework to understand biodiversity and in particular how biodiversity varies across different environments. (communities) -Biodiversity - biggest buzzword -Indicator of health of ecosystem -Community is an assemblage of species Approximately 1.75 million species already described. Estimates range from 10-100 million species total. Species density (# of species per unit area) varies dramatically between different ecosystems.

Atmospheric CO2 and Temperature

What is the evidence for a correlation between atmospheric CO2 and temperature? -There is well documented historical connection between CO2 and temperature, as determined in ICE CORES. -CO2 : air trapped in bubbles in the ice. -Temperature: deuterium levels in water linearly correlated with temperature Temperature always changes as CO2 rises. Does not mean causatively related.

The mechanism

What is the mechanism to explain higher diversity when disturbance or predation is present? -Disturbance precluded equilibrium -Competitive exclusion prevented? --Note the recessive of a LV model that include K, a, and P -Culminated in the: ---Intermediate disturbance hypothesis

Mutualism and ZGI: Dual obligate relationship

When dN1/dt=0, there must be some number of species 2 (N2) in order for species 1 (N1) to survive. 1. Minimum number of species 2 for species 1 to exist (0 growth) 2. As more of species 1 are added, more and more of species 2 are needed to supply them. Same situation for species 2. 1. Minimum number of species 1 for species 2 to exist 2. As more of species 2 are added, more and more of species 1 are needed to supply them. Combine: both will fall to extinction Zone a = growth of N1, decline of N2 Zone b = decline of both Zone c = growth of N2, decline of N1 But realize! In such a strong obligate relationship, 1 can't exist without the other Intense species interaction (even a mutualism) leads to instability No place where there is 0 growth: Neediness

Shifting gears away from population ecology to community and ecosystem ecology

While we will now emphasize concepts like community and/or ecosystem diversity, realize that these conglomerations are still made up of populations of species. Natural selection continues to act on the individual phenotypes resulting in evolution of allele frequencies of those populations Ecosystems are just a bunch of communities

Concepts of photosynthesis, optimal foraging, predation

Why are these important as we think about ecosystems? Autotrophy and heterotrophy are how energy is transformed and flows through ecological systems. These are many of the strategies that organisms have evolved to deal with gaining and losing (optimizing) energy.

How wolves change rivers video

Wolves eat herbivores Vegetation left alone stabilizes near the river

Disturbances

fire, clear cuts

Succession

temporal dynamics of community structure