Department of Biology, University of Ottawa Ottawa, Ontario, Canada
Biotic interactions affect community level processes and structure. Through the study of metacommunities, which encompass networks of communities connected by dispersal, ecologists can advance our understanding of communities while incorporating landscape-scale processes. Investigating how multitrophic interactions, such as predatory and mutualistic interactions, structure metacommunities is an exciting frontier of knowledge. The exploration of this topic will not only further understanding of ecological dynamics but also provide tools for conservation and restoration. We investigated the impacts of predators and mutualists on a butterfly metacommunity, as well as the impacts of local and landscape characteristics across three trophic levels: butterfly predators, butterflies, and flowering plants. Using data for butterfly diversity/richness, flowering plant diversity/richness, and predation (on clay butterfly models) across 15 grassland sites, we asked 3 questions: 1) How do predation pressure, mutualist metacommunity structure, and local and landscape habitat characteristics affect butterfly metacommunity structure? 2) How do local and landscape habitat characteristics affect predation pressure? 3) How do local and regional habitat characteristics affect flowering plant metacommunity structure?
Butterfly diversity and richness increased with floral diversity and richness, and floral diversity and richness rose in larger sites. Unexpectedly, predation pressure, as measured experimentally, did not affect butterfly communities, nor did any local/landscape variable. Predator attack frequency showed marked variation, and attacks were more common in both larger and more isolated sites. While predation is clearly present in this system, predators may track landscape characteristics rather than characteristics of prey communities. This decoupling of predation pressure and butterfly community diversity suggests that conserving and restoring healthy predator populations will not harm butterfly communities, although caution is required in situations where at-risk butterfly species may be present.