Population Ecology

Question 1

7. How is population regulation measured? What are the factors that appear to be most important in regulating wild populations? You may restrict your answer to a particular taxonomic group. Is density-dependent population regulation a “law” of ecology?

Question 2

8. Why are small populations more likely to go extinct?

Answer 2

• Genetic drift
• Environmental stochastic events
• Inbreeding depression; deleterious alleles rising to fixation
• Genetic hetero- and homozygosity
• Gene flow (lack of)

Bonus:
- Genetic rescue, evolutionary rescue
- Minimum Viable Population size
- Effective versus census population size
- Allee effect (positive density dependence)

Question 3

9. Define the term metapopulation. (a) What are the factors that characterize metapopulations, and what conditions need to be satisfied in order for metapopulations to persist? (b) Describe what data you would collect to test whether populations in a fragmented habitat were behaving as a metapopulation.

Answer 3

• Define metapopulation: gene flow between local populations, a “population of populations”
• Factors and conditions of metapopulations: balance between local colonizations and extinctions, suitable habitat patches (even unoccupied ones), replacement condition (colonizations must be greater than extinctions), large and well-connected networks of populations, habitat patches close enough for migration to occur
• Testing for metapopulations: Genetic samples, Track migration events, Survey landscape to identify habitat patches, Spatial data to determine connectivity of patches, Incidence function model (IFM) to model metapopulation dynamics
• Could include examples: Fritillary butterflies are a classic

Question 4

10. How is propagule pressure related to the success and impact of invasive species or species with extremely broad geographic ranges? Discuss both evolutionary and ecological hypotheses that can explain the link between propagule pressure and invasion.

Question 5

11. What factors limit the geographic range of species? Are the borders constant? Do you expect the same factors to operate along the different margins of a species’ distribution?

Answer 5

• gene flow preventing local adaptation
• trade-offs
• lack of resources
• barriers, both physical and biological
• borders fluctuate

Question 6

12. What are the Lotka-Volterra equations and how have they been used to advance ecological theory? When do they work well as predictive models and when do they help provide insight into mechanisms of population changes?