1. ESC 556 week 11 Conserving Populations

2. Various levels of conservation Species  populations  73% of 2290 plants in NA, < five populations  Informed action for conservation 1. Factors controlling population density 2. Identification of threats 3. Predict the effects of management actions

3. What is a population? Fixed geographic area Convenience to the investigator Scale Populations description  Density  BIDE  Structure

4. Monitoring Demographic Structure States of development  Plants: juveniles, seedlings, reproductive, senescent  Marsh gentian  Invasive (bare soils), regressive (high ground cover percentage) Individual counts

5. Census data Census data vs. survey data Spider orchid 80% decline in 50 years Endangered in Britain Chalk & limestone grassland Cattle vs. sheep grazing

6. What is rarity? Some species naturally rare Changes in population size Classifying types of rarity  Size of geographic range  Habitat specificity  Local population size Barn owl Ospreys

7. Causes of Rarity Anthropogenic effects Patterns in the ecology of rare species Poor dispersal abilities (sedentary species)  Plants, invertebrates  No migration to favorable habitats Deterministic vs. stochastic process External and Internal Influences

8. External Influences Habitat Change Other organisms Direct Human Influences Environmental Contaminants Environmental stochasticity

9. Habitat Change Complete destruction to conversion to less suitable 36% of all animal extinctions 100 species/day Climate Habitat management

10. Other organisms Introduced species Coconut moth and its parasitic fly in Fiji Thistles and herbivores Introduced diseases

11. Direct human Influences Commercial exploitation Persecution Recreational hunting Non-target species Disturbance

12. Environmental Contaminants DDT Bioaccumulation, biomagnification, biotransformation

13. Environmental stochasticity Local climate  Ectothermic species  Endoterms affected indirectly Natural catastrophes Effective independently of population size

14. Intrinsic Factors Demographic stochasticity Genetic stochasticity  Loss of heterozygosity  Inbreeding depression  Genetic Drift  Outbreeding depression  Minimum Viable Population  Effective Population Size

15. Demographic Stochasticity Excluding external influences  fecundity & mortality Large population  predictions possible Small number  chance effects Affect social functioning  Defence, migration, lekking Allele effect

16. Genetic Stochasticity Genetic uniformity a disadvantage Loss of Heterozygosity  Allele  h j = 1 – Σp ij 2  Recessive lethal alleles  Differences between groups of organisms  Results in inbreeding depression

17. Genetic Drift Chance loss of alleles H t+1 = H t (1-(1/2N)) Bottlenecks vs. Founder events

18. Genetic Drift

19. Outbreeding Depression Outcrossing between divergent populations Incompatibilities between local genes Mountain ibex - two subspecies

20. Minimum Viable Populations Critical minimum size MVA Survival probability over time Different between species & even populations Environmental stochasticity 50 – inbreeding depression 500 – genetic drift 50-100 individuals

21. Effective Population Size 50-500  Based on certain assumptions N e = 0.75N Grizzly bears (38 instead of 200) 0.4 – 0.05

22. Summary of Influences External events Catastrophic events Demographic stochasticity Importance of genetics  Ex situ conservation Extinction vortex  Heath hen < 50 inds.  2000 but fire, harsh winter, predation, inbreeding depression

23. Interaction of factors Large Blue 50% lost by conversion < sheep grazing + < rabbits  more vegetation Vegetation  ant (Myrmica sabuleti)  butterfly

24. Prediction Models Limitations  Sufficient data  Replication PVA  Probability of survival for a number of generations  The model Population survival time Evaluation of management options Monitoring the results Northern spotted owl, grizzly bear Keystone species Small population paradigm vs. declining population paradigm

25. Spatial perspective Fragmentation  Size and distance of patches (habitat islands)  Size – species diversity  Distance – recolonization probability Population decline  intrinsic effects Some +ve effects

26. Metapopulations Rate of recolonization vs. rate of extinction Metapopulation persistence  Number & size of populations  Dispersal rate  Smaller – more isolated populations  Temporally independent extinctions  Regionally acting environmental factors

27. Metapopulations Types of meta-populations

28. Ranges Population parameters vary  Center vs. edge Center: optimal conditions  Birth rate > death rate  Edge  equal rates  Outside  only through emigration (Source and sink)

29. Conservation Implications Small populations not always expendable: Source- sink situation Habitat destruction @ the core Range size & population density correlation

30. Corridors Connecting the patches – seminatural habitats e.g. disused train lines within agricultural landscapes Global change corridors Pros  Increase species richness  Encourage recolonization (Rescue effect)  Reduce genetic problems (e.g. inbreeding depression) Cons  Spread disasters  Outbreeding depression  Large & Expensive

31. Role of Reserves Central National Parks or smaller sites SLOSS Metapopulation considerations Design and Dispersal The shape – Edge effect Not the solution for many species Low percentage

32. Recovery Measures Extinction in the wild definite, then what? Captive breeding & Reinroductions Zoos All individuals  California condor, black-footed ferret 1000 individuals 2000 land vertebrate species in the next 200 years Small populations  Control of matings  maximize genetic diversity  Inoculations from outside Differentiation in captivity

33. Captive Breeding Gene Introgression  Przewalsky’s horse by domestic horse  European bison by cattle  Different subspecies Behavioural factors  Cultural transmission  Predator avoidance At introduction  Removal of the external factors  Numbers of individuals, how many sites, when  Probe releases

34. Translocations Transfer from one site to the other True introductions, reintroductions, augmentation Limited dispersal powers & fragmented habitats High population increase rate  Not good for mammals and birds High genetic diversity Best at historical core range Invertebrates

35. A Way Forward Not all species can be protected Charismatic species Which groups to concerve? Umbrella species Keystone species Hotspsots  Global & Local