Diversity in motion: the influence of dispersal and metacommunity spatial structure on invertebrate communities in Heliconia phytotelmata
A recent trend in community ecology is to investigate the influence of dispersal (a regional process) on the structure and formation of communities. Dispersal of individuals is important not only for colonization of habitats, but also for maintenance of diversity within communities, as dispersal can influence local species interactions. Herein, I examine the role of dispersal from two viewpoints using a metacommunity of aquatic invertebrates that inhabit inflorescences of Heliconia imbricata (Zingiberales: Heliconiaceae). First, I examined the response of local communities to changes in metacommunity spatial-structure, including an analysis of the effect on community development. In these detritus-based communities where positive interactions are dominant and dispersal limitation is common, spatial isolation decreased local species richness, altered invertebrate composition, and increased turnover. Additionally, spatial isolation and community development (succession) had an interactive effect on species richness and turnover, thus indicating that dispersal has important predictive impacts to succession not previously documented. These studies were conducted in secondary forest locations where prior land-use practices have affected forest regeneration and consequently the spatial structure H. imbricata. Hence, this has relevance to studies of habitat fragmentation, and demonstrates the usefulness of metacommunity ecology to conservation biology. Second, I examined whether dispersal by a single species can impact community formation (priority effects) leading to development of alternative community states. Using a combination of mark-recapture techniques and correlational as well as experimental studies, I tested the effect of a primary consumer, Cephaloleia puncticollis (Coleoptera: Hispinae), on local community structure and investigated consequences of dispersal by C. puncticollis on community-level diversity. Results showed that C. puncticollis larvae, but not adults, affect invertebrate community structure. At the landscape level, greater C. puncticollis abundance within patches increased invertebrate species richness and altered composition by increasing predators and detritivores, resulting in two community types. Overall, invertebrate communities within H. imbricata inflorescences are affected by the positive interactions of C. puncticollis, though effects are varied in space and correspond to dispersal of individuals. While many other factors contribute to patterns of diversity in this system, this study demonstrates the importance and combined effects of local and regional processes on ecological communities.