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Chapter 10 Islands of Nature and the Role of Dispersal

Discussion Questions

1. How is destroying habitat patches in a metapopulation analogous to vaccinating individuals against an infectious disease to prevent an epidemic? The way to approach this question is to think of each individual in a population as a habitat patch for a disease pathogen. The effect of vaccination is to remove habitat patches for pathogens—because once an individual has been vaccinated, that individual is no longer available for the pathogen to colonize. Now, considering the metapopulation model explained in this chapter, recast the model in light of when vaccination might cause a disease to disappear from a population.
2. What might metapopulation theory contribute to a discussion about the construction of dams in rivers and the impacts of these dams on aquatic populations?
3. In view of political realities, do you think it is easier to set up a system of protected areas consisting of many small patches or one large patch? In your discussion, consider opportunities, management costs, vulnerabilities incurred with different scenarios, and compatibility with human economic activity and development.
4. A set of three subpopulations has the following allele frequencies (assume only two alleles exist for the gene of interest): p1 = 0.5; p2 = 0.2; p3 = 0.6. Calculate FST. What does this calculation tell you about the subpopulations?
5. Imagine a set of three subpopulations connected by some migration and with some turnover of patch occupancy. Assuming that pe= 0.2 and c = 0.6, construct a graph that shows the equilibrium fraction of patches that would be occupied in this metapopulation. What is f* for this metapopulation?
6. The population of speckled burrowing cats (an imaginary species) has dwindled for years. These cats are now extinct in the wild, but fortunately you were smart enough to collect a few individuals before it was too late. You have bred these cats in captivity for four generations and now have about 70 individuals. You intend to reintroduce 50 of them into the wild, but you have to choose between two plans: (A) release 10 individuals at five different sites with at least 30 miles between sites, or (B) release all 50 individuals at a single site. What are the major risks for each of these plans? What more would you want to know before making your decision?

Group Projects

• Propose a potential corridor project in your area. Specify the two protected areas that would be connected and the species you hope would use the corridor. Now produce a table of the critical data you would want to collect on the lands that the corridor might run through, and discuss how you would use these data to design the most cost-effective corridor possible.

• Use the Internet to read the latest debates and news about legislation to protect roadless areas (e.g., the U.S. Roadless Area Conservation Act of 2009). Now use the scientific literature to assess the biological data indicating that roads fragment populations. Choose one species to research in depth, and describe the hard evidence suggesting that roads do or do not significantly harm this species.

Useful Websites

• CorridorDesign, a website hosted by Northern Arizona University, offers downloadable GIS tools and information for designing wildlife corridors. http://www.corridordesign.org

• Golden Lion Tamarin Association (Associação Mico-Leão Dourado) provides information on fragmentation of the Brazilian Atlantic Forest and the on-going efforts to restore dispersal corridors for tamarins. http://www.micoleao.org.br

• ProtectedPlanet is the online interface for the World Database on Protected Areas, which is the most comprehensive global dataset on marine and terrestrial protected areas. The site includes a searchable visualization tool and links for downloading the entire protected areas database. http://www.protectedplanet.net/

Suggested Readings for In-class Discussion

• Delaney KS, Riley SPD, Fisher RN (2010) A rapid, strong, and convergent genetic response to urban habitat fragmentation in four divergent and widespread vertebrates. PLoS ONE 5: e127675: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0012767 (open access)

• Gibson L, Lynam AJ, Bradshaw CJ, He F, Bickford DP, et al. (2013) Near-complete extinction of native small mammal fauna 25 years after forest fragmentation. Science 341: 1508-1510.

• Lesbarrères D, Fahrig L (2012) Measures to reduce population fragmentation by roads: What has worked and how do we know? Trends Ecol Evol 27: 374-380.

• Wearn OR, Reuman DC, Ewers RM (2012) Extinction debt and windows of conservation opportunity in the Brazilian Amazon. Science 337: 228-232.