Fish Predation Alters Community Predictability in Small Ponds

by Biro, Elizabeth Gabor

Predation can have large but variable impacts on prey species diversity. Although the effects of predation are often deterministic, stochastic processes can often influence the outcome on community assembly regardless of predator presence. Top predators can alter several properties of the community, including the abundance and richness of species, as well as the traits of species that can persist with predators. These properties, in turn, may influence the pattern of community assembly and the predictability of community structure from site to site. In this study, we investigated whether the presence of fish predators influenced the site-to-site predictability (similarity in community structure) of invertebrate and amphibian communities in small ponds. First, we surveyed a series of ponds in natural areas that varied in their presence of fish predators and examined local and regional species richness, as well as site-to-site variation in community similarity (i.e., ?-diversity). Second, we established a mesocosm experiment in which we introduced fish to one-half of the arrays, and compared their community similarity. In both cases, the presence of fish reduced both local and regional species richness, but importantly, they also caused communities to become more similar in community composition. Thus, fish made communities more predictable from site to site. We conclude that the presence of top predators can alter the relative importance of stochastic versus deterministic processes in the assembly of communities. Key Words: Community assembly, predation, beta-diversity, local richness, regional richness, fish, Green sunfish, Lepomis cyanellus Biro, Elizabeth, 2007, UMSL, p. 5