ECOLOGICAL NICHES
The abundance of potential ecological niches affects species richness. A more complex community provides more potential ecological niches than a simple community. Natural selection favors those individuals of a species that avoid or reduce competition for resources. Each species' niche differs from the others because resource partitioning reduces competition among coexisting species. In tropical forests, fruit-eating birds, primates, and bats coexist in the same habitat. Several hundred bird, primate, and bat species eat primarily fruit but the different species specialize on a wide variety of fruits to reduce competition. Similarly, resource partitioning can take place, with different bird species foraging in separate areas of a single kind of tree.

Increasing structural complexity of the habitat also amplifies species richness. Complex vegetation (such as a forest) provides more kinds of foods and hiding places than a less structurally complex community (such as a desert).