Trade-Offs, Food Web Structure, and the Coexistence of Habitat Specialists and Generalists

Species differ greatly in the breadth of their environmental distributions. Within the same collection of habitats, some species occur in many habitats, while others are only able to exist in one of a few. Trade-offs in the abilities of species to perform in various ecological interactions are important both to facilitating species coexistence within a habitat and to limiting the distributions of species among habitats. In this article I use a food web model to explore how in the same collection of habitats some species may be limited by trade-offs to occupying only one habitat, while other species may face no trade-off between habitats and therefore be able to generalize in their habitat use. Food web interactions define the available niches within a habitat. Changes in food web structure cause some niches to be lost and replaced by other niches as one moves between habitats. Species occupying these niches will have more limited habitat distributions. However, other niches may be available in the food web structures of multiple habitats, and species occupying these niches will have broad habitat distributions. Understanding the structure of trade-offs within and between communities is fundamental to predicting the types of species with broad or narrow habitat distributions.