Love those SDP2 projects!

ObjectivesConservation approaches: populations/species entire habitats Conservation biology relates to landscape ecologyHabitat destruction/fragmentation causes much extinctionPlans for preserves Size, number, shape, step stones, corridors Preserve community structure

Conservation Planning: Approach 2Preserve habitats/areas, especially biodiversity hotspots high species number high endemism

Endemic species: restricted to small geographic area; especially prominent on islands

Little spatial relation between species richness, threatened species, and endemic speciesSpecies richness Threatened speciesEndemic species

Habitat changes caused by human land use limit conservation strategies.

Deterministic causes of extinctions:the evil quartet1 habitat destruction and fragmentation (67% of cases)2 introduced species3 overkill (overexploit)4 chains of extinction

Habitat reduction and fragmentationlead to endangered species

Species introductions (e.g. this predatory snail) can eliminate native species.

Decline in marine organisms and increase in eutrophication due tohuman cultural development

Overexploitation changes species composition of this marine community.

Whalers shifted to new, less profitable species as populations of heavily hunted species declined.

Smaller fragments support fewer animals.

Figure 1

Habitat reduction and eliminationSome habitats are eliminated altogether.Fragmentation causes other problems: reduced total area reduced habitat heterogeneity reduced connectivity greater inter-fragment distance unable to migrate with changing climate reduced interior/edge ratio

Principles for design of nature preserves:If create preserve from large expanse of uniform habitat:larger is better than smaller SLOSS: single large or several small?one large area is better than several small that sum to same sizeadd corridors or stepping stonescircular is better than elongate with more edge

*** What is the pattern? What explains it? Figure 2

Which sizeof area isneeded?Will a park beSufficient?

Why are larger areas better? support more species by reducing likelihood of stochastic extinction promote genetic diversity buffer populations against disturbance avoid edge effects offer freedom to migrate

***Summarize two major results.Corridors enhance migration between patches and maintain population cohesion.Figure 3

***What are advantages of corridors?Increase immigration increase species richness provide a rescue effect prevent inbreeding; add genetic diversityIncrease foraging area for widespread speciesProvide cover for escape from predator when movingAlternative refuges from large disturbancesMix of habitats for species requiring them

Are there disadvantages?

If creating preserve out of diverse habitat:Several small in different habitats better than one large in uniform habitatPlan for migration ---> use corridors stepping stones to link habitats bridge roads and pipelines that impede movement

Consider community structure

Top-down control of trophic abundances Cascade effects: indirect effects extended through multiple levels Can have chain of extinctions if highly dependent Keystone organisms must be preserved Non-redundant species, key species that maintain stability/diversity

***What are conservation implications of the two contrasting models? Rivet/redundancy

Would focus be on community dynamics or single-species dynamics?In which model are keystone species important?

How does species (and functional diversity affect community response to disturbance?

Community PrinciplesAn increase in the structural diversity of vegetation increases species diversity.Disturbance may be necessary to maintain all diversity.When disturbed, greater diversity leads to greater stability.Full restoration of native plant communities sustains diverse animal populations. A high diversity of plant species assures a year- round food supply for the greatest diversity of wildlife.Species survival depends on maintaining minimum population levels (>500).

Sample exam ?You are asked to design a national park system for a tropical country.1) How will the concept of hot spots of diversity influence your choice of areas to conserve?You have defined your locations. What are 4 principles that you will consider in the next phase: their spatial design?What specific attributes of parks are needed to accommodate specific flora or fauna?What general criteria related to preserve size must be met to ensure long-term survival of species? (assume habitat requirements are met)

Population models assume: large size (> minimum viable population size); no variation in average birth and death rates.

In reality, randomness affects populations, especially small ones: Catastrophe Variation in environment Stochastic (random sampling) processes

Chance events may cause small populations to go extinct.

Probability of extinction increases over time; increases with smaller initial population size.Small populations are more likely to go extinctdue to random fluctuation in population size.Figure 4

***Summarize the two main results. Provide a reason for each result. What traits enable a population to rescue asmall population from extinction? Figure 5

Rescue effect:Immigration from a large subpopulation can keep a declining subpopulation from inbreeding and going extinct.

Can produce positive density-dependence: survival of subpopulations increases with more subpopulations.

Mainland-island model:Source provides emigrants to sink.sourcesinksFigure 6

Spatial PrinciplesLarge areas sustain more species than small areas.Many small patches in an area will help sustain regional diversity.Patch shape is as important as size.Fragmentation of habitats, communities, and ecosystems reduces diversity.Isolated patches sustain fewer species than closely associated patches.Species diversity in patches connected by corridors > than for disconnected patches.A heterogeneous mosaic of community types sustains more species, including rare species.Ecotones support a variety of species from both communities & species specific to the ecotone.

*******Currently 7% of land area preserved; goal = 12%Hotspots occupy 1.4% of total land area but hold 44% of plant sp and 35% of terrestrial vertebrates. Within hotspot 88% of natural vegetation has already disappeared. Tend to have above-average human densisites and high pop growth rates.****Birds****Chains of extinction: Secondary extinction following a primary extinction.Other species depend on first species - doomed too, especially if obligate specialist relatinship.Large predators go when prey go etinct e.g in New Zealand, forest eagle goes when prey (moas) went extinct eg. Black-footed ferret declined when prairie dogs declined.**Golden lion tamarin**********K19.8 Squirrels nesting in woodlots Drey = nest**Ktable 19.3 Habitat change - and consequences for population dynamics****K19.7 # of shrew species on islands of different size (natural emigration and extinction)******K 19.10 variegated fritillary = butterfly movement with and without corridorsCosts to corridors:disease transmission, conduct fires, expose to more predation risk**Ktable 19.4 Disadvantages too: Faciliate spread of epidemic diseases, pests, exotic species, weedsDisrupt local adaptations and cause outbreeding depressionFacilitate spread of fire; encounter predator**********Community Principle OneFull restoration of native plant communities sustains diverse wildlife populationsa. physical conditions of a particular site determine what community of plants will survive for the long term without special careb. when confronted with a previously farmed or otherwise disturbed area, it may be difficult to determine the vegetation history of the sitec. soil series on a site is one of the best clues to the original vegetationd. restoring the fullest possible complement of the plant species that would most likely have occupied an area originally, while retaining the characteristics of the site needed to maintain its human uses, results in an increase in native animalsSummary: Full restoration of native plant communities sustains diverse wildlife populationsThe more fully restored natural community has a higher diversity. This means introducing as many components of the natural community as possible.

****Chance exerts more influence on small pop: Coin = individual; if get tails = death.Pop of 5 vs. 10 coins; pop of 5 has greater chance of extinction (1 in 32 series of 5 tosses getting all tails) than pop of 10 (1 in 1024 of getting all 10 tosses as tails).Whether an individual dies or raises young in given time depends largely on chance.Even with 10 individuals, there is a finite probability that all individual will die; 10 tails of 10 flips.**Extinction due to random fluctuations in population size.B = d = 0.5 gives this pattern. Pop = initial pop size.Start at pop size 10, and go vertical; with increasing time--> > prob extinctionStart at 1000 at 0 prob extinc. And move to left; larger pop have no prob of extinction over short periods.Start at green t = 100 intervals, probab of extinc decreases as greater initial pop size

**Patches of dry, nutrient-poor grassland along German rivers. Each colored dot = 1 species.1956: 143 patches and abundances of plant species recorded. Surveyed again in 1988.Each color = 1 species. 1 dot = Average in 1956 of subpopulations for a given species that went extinct or average in 1956 of subpopulations for a given species that survived.Larger populations were less likely to go extinct.Depending on sp, between 30% and 85% of subpop in 56 were absent in 88. Between 2% and 44% of patches empty in 56 were colonized by 88.Small pop vulnerable to random env. disasters: or low gen variation Closer rescuing pop, greater likelihood of immigration to sink.Pop traits: large pop size; close to small pop, connected by corridor; has genetic variation; BR>DR so immigrants.

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**Serpentine soil grasslands in CA. Habitat patches function as potential pop sites for checkerspot butterflyLarge pop at Morgan Hall probably serves as a continual source of colonists for other small patches.Examples of simple island-mainland model**