Conservation Biology
Example of departure from nestedness - plants in U.S. remnant parries and forests
1) archipelagoes of small sites contain more species than single large sites of equal total area 2) no species excluded from small sites 3) rare species more often found in small sites
Patterson and nestedness
1) extinction is nonrandom 2) species composition of small habitat fragments converges In small patches 3) widespread generalists survive 4) local, rare ones don't Conclusion - we need larger reserves
Anthropogenic extinction causes
1) habitat destruction - agriculture - forestry - desertification (desert actually spreading) - salinization 2) introduced species 3) hunting 4) climate change
Species most vulnerable to local + regional extinction
1) naturally rare species - low densities or limited geographic distributions 2) wide-ranging species 3) non-mobile species 4) species with low fecundity (offspring) 5) species dependent on patchy or unpredictable resources 6) interior species (edge avoidance) 7) species vulnerable to human exploitation
Community theory and conservation
1) reserve design 2) species area relationship and island biogeography directly applicable 3) SLOSS debate
Habitat fragmentation: factors affecting diversity
1) time since isolation 2) degree of isolation - distance from unfragmented habitat - distance from other patches 3) crowding effects - mobile species move to remaining fragments
Oak masting
All over reproduce acorns one year - mice pop. increases, predator pop. increases... so not all acorns consumed - following years normal production
Human caused extinction
Anthropogenic extinction
As ecosystem gradually change, ____ extinction occurs
Background
Stochasicity
Chance events that change pop. size - fires, diseases, storms - may cause extinction
For a population of a certain size, what is the probability of extinction?
Depends on birth rate, death rate, and starting pop. size - probability of 1 = 100% extinction - the larger the pop. the smaller the probability of extinction
Example of probability of extinction
Do the math silly
Age structure
Ethiopia lots of young people so population growing - other graph less babies so pop. expected to shrink
Small disturbances cause ___ of local populations
Extirpation
Habitat island faunas tend to form nested subsets
Faunas on small patches tend to be nested of larger patches - if true, the SL > SS
Edge effects and reserve design: what shape is best?
Forest edges - modified immigration/emigration; reduced rescue effect Altered microclimate 1) daytime temp higher, nighttime temp lower 2) humidity reduced 3) problems worse at high latitudes (solar angle) 4) secondary growth can help 5) shade tolerant species lost
Departures from nestedness
If sites are non-nested OR if small sites contain more species... SLOSS debate is not settled
Another example of nested subset model
Large islands have more species
Large natural catastrophes have causes ___ ___
Mass extinctions
Population viability analysis
More than just population models - PVA models include: 1) available habitat area 2) predicted human population expansion 3) habitat quality 4) interconnected metapopulations * guide management decisions
Ultimate causes of extinction
Population extinction risk is affected by - population size - geographic range (small range more likely to go extinct) - age structure - sex structure - life history (how often reproduce) - stochasticity
Central aim of conservation
Prevent extinction
Yellowstone grizzlies: why did their population recover?
Reintroduction of 41 wolves in 1990s - wolves kill elk... can't defend its kill from a bear, or bear gets leftovers - pop. went from 35 to over 500 (deemed recovered)
SLOSS debate
Single Large or Several Small (nature reserves) - which hold more species - large or small sites? - answer is difficult: jaguar may not be able to move b/w patches but bobcats can
Pseudoextinction
Sp1 evolves to Sp2... Sp1 no longer exists
Natural extinction
Species evolve, flourish, and go extinct
Life history: California Condor
Victims of life history? - don't reproduce regularly - only have 1-2 babies per cycle - associated with parental care - K selection works best at high density
Why does extinction happen?
When species fail to adapt - species adapt slowly be evolution - humans change ecosystems rapidly - change outpaces adaptation
Edge effects
Wind speed increases transporting pests and disease Water flux modified - interception of water by plants changed - evapotranspiration modified
Yellowstone grizzlies: why did their population decrease?
Yellowstone closed off garbage dumps - perhaps started to starve, then recovered
SLOSS is ___ specific
context
Bigger islands generally have more species, but not always perfectly nested
ex. island that's 65 units has species island that's 118 units does not
