Habitat selection by two competing species in a two-habitat environment.

We present a theoretical study of habitat selection strategies for two species that compete in an environment consisting of two different habitats. Our fitness functions are derived from the Lotka-Volterra competition equations, and we assume that individuals settle in the habitat in which their fitness is maximized. We derive an ideal free distribution across the habitats for both species. Our model provides analytical and graphical descriptions of individual habitat selection behavior, isolegs (the boundary lines separating regions where qualitatively different habitat preferences are predicted), and spatial population distributions. Our analysis reveals complex isolegs, several novel patterns of habitat distribution, and even situations where spatial strategies, as well as the relative abundances of coexisting species, exhibit only local stability. Hence, distributions of competing species may be determined not solely by their respective densities but also by the order of colonization. This happens, however, only for extreme levels of interspecific competition. In the situation where one competitor species is dominant over the other, our model predicts isolegs that qualitatively agree with observed behavioral patterns. However, our model predicts a greater variety of possible situations than has been previously described. Finally, we analyze the influence of habitat selection behavior on species isoclines and verify that increasing interspecific competition leads to habitat segregation.