Great Basin Naturalist


The distribution of 21 species of nonvolant mammals among nine islands in the Great Salt Lake was analyzed for biogeographic patterns. The number of species inhabiting an island is closely correlated with island area That the slope of the regression line describing this relationship (z or b) is relatively shallow compared to (1) totally isolated island systems or (2) island systems where an equilibrium between rates of colonization and extinction have been attained suggests that isolation plays little role in accounting for the variation in mammalian species diversity among islands. Stepwise multiple regression confirms this, while demonstrating that area alone accounts for 88 percent of the variation in species diversity among islands. However, endemic subspecies comprise a significant proportion of the insular mammalian fauna, suggesting that isolation for small mammals restricted to certain habitats may be substantial. A general scenario of the processes determining insular mammalian diversity and endemism is discussed for the Great Salt Lake, where the dynamic lake level creates a potential for different biogeographic processes over time.