Chapter 6 Content FRQ The California Department of Fish and Game is developing a plan to connect mountain “habitat islands” that are separated by open areas of flat, arid land in the deserts of southeastern California. These mountain areas are habitats for desert bighorn sheep (Ovis Canadensis), which move extensively among the islands through habitat corridors. The habitat corridors provide opportunities for recolonization, seasonal migration, and maintenance of genetic variation among the metapopulation of desert bighorn sheep.

(a) Explain what is meant by a metapopulation and how it relates to the desert bighorn sheep. (1 point) A metapopulation is a group of separate, isolated populations that have individuals occasionally disperse between the habitat islands, allowing recolonization of islands that might go extinct.

(b) Identify two density-dependent factors and one density-independent factor that could affect the populations of desert bighorn sheep. (3 points) Density-independent factors: • Drought • Fires • Storms • Mudslides • Freezes Density-dependent factors: • Scarcity of food resources • Disease • Crowding • Increase in predators • Competition for mates

(c) Explain the consequences to the desert bighorn sheep population if the plan to connect the mountain habitat islands is not implemented. (2 points) If the plan to connect the mountain “islands” is not implemented, the following could occur: • Because the smaller isolated populations are more prone to extinction. They could not be recolonized without dispersal from neighboring islands. • Dispersal from neighboring islands could also bring additional genetic diversity which could help an isolated population persist.

(d) Explain how the theory of island biogeography applies to the mountainous areas of southeastern California. (4 points) • The larger the area of the mountain “island” with more different types of habitats, the greater is the number of species that will be present. • The larger the area of the mountain “island,” the larger are the populations of given species; larger populations are less prone to extinction. • The more connected the mountain “islands,” the greater the chance for dispersal or migration of species, resulting in higher rates of immigration of new species.