PARENT SESSION
Organized Oral Session 39: Consequences of dispersal and colonization: What happens when communities are opened?
Organizer(s): CG Guthrie and DA Yee
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 516 C, Level 5, Palais des congrès de Montréal

Succession in Heliconia phytotelmata: Spatial structure of the metacommunity impacts local versus regional processes in community development.

Guthrie, Carla^*,1, ¹ Integrative Biology, Austin, Tx, USA

ABSTRACT- For decades, ecologists have debated the importance of assembly rules for community development. In the early years, like much of community ecology, the debate focused on local processes, but more recently has included regional processes. Using a metacommunity framework, I investigated the hypothesis that the impact of local processes on community development varies depending on the rate of dispersal into the community. Differing land-use histories in the forests of Corcovado National Park, Costa Rica, have altered the spatial structure of tree fall gaps and consequently the degree of spatial isolation among gap-dependent communities. This change in forest structure provided a chance to examine the role of patch isolation (a proxy for dispersal) on successional dynamics. Using an aquatic invertebrate community that inhabits inflorescences of Heliconia imbricata, I examined changes in community structure for early, mid- and late successional stages of bract development. In 2003, invertebrate communities were collected from three forest areas with differing patch structures of H. imbricata. This corresponded to three levels of patch isolation; high (natural patch density), low isolation (high patch density) and no isolation (one mainland patch, ca. 25,400m²). Analysis of univariate community measures (abundance, species richness, diversity and evenness) and multivariate analyses showed that patch isolation significantly influenced invertebrate composition in early and mid-successional bracts. Late stage bracts were similar in composition and not affected by isolation. For each level of isolation, invertebrate compositional turnover was highest among young bract communities (70-61%) and lowest among late successional bracts (57-53%). Moreover, the rate of compositional turnover changed with the spatial structure of Heliconia patches. Turnover was highest among communities from isolated patches and lowest at the mainland site. These results suggest that the stochastic effects of colonization are important during early successional stages, more so for communities isolated in space. As succession proceeds, compositional changes follow a deterministic path and isolation becomes of minor importance to community structure.

Key words: invertebrate community, dispersal, Heliconia imbricata, spatial structure