PARENT SESSION
Tuesday, August 8, 1:30-5:00 pm
COS 39 - Community ecology II: community dynamics and change
L-3, Lobby Level, Cook Convention Center
Presiders: K Beard and Y Wang

Relative abundance in forest Lepidopteran larval assemblages: trait-based mechanisms and macroecological patterns.

Lind, Eric^*,1, Barbosa, Pedro¹, ¹ University of Maryland, College Park, MD

ABSTRACT- Recent advances in theoretical ecology have attempted to explain long-observed patterns of species abundance in a given local site, specifically that species assemblages are characterized by high numbers of scarce and rare species, and a few abundant species. A key question for understanding the origin of these patterns is whether those species occurring consistently in low numbers are somehow inherently different from more abundant species in the assemblage, as predicted by niche assembly models. Using a phylogenetically informed approach, we examine life history traits predicted to influence relative abundance in an assemblage of temperate forest Lepidoptera, to determine which if any traits are associated with species abundance levels. Using a five-year survey of larval abundance, we examined traits predicted to impact population growth such as fecundity, larval growth rate, parasitism level, and dispersal (quantified by wing loading, a proxy measurement). Initial results indicate taxon-specific relationships between mean trait values and abundance in related species, but no consistent predictor of abundance in the assemblage. Neutral theoretical approaches to community assembly, while recognizing species differences, emphasize the importance of shared, stochastic processes such as dispersal limitation in structuring communities. We use two approaches to characterize the importance of dispersal to the observed abundance patterns. First, by comparing individual species abundances against a Poisson process, we delineate regular from random arrivals, and show the assemblage of herbivores to be strongly impacted by transient species. Second, using a likelihood-based curve-fitting approach, we fit the data to selected models of abundance distribution, and show the lepidopteran assemblage to be consistent with a zero-sum multinomial (ZSM) distribution as predicted by Hubbell's neutral theory, fitting as well or better than the other models. The best-fit ZSM parameters for the assemblage also indicate the local assemblage to be well connected to the metacommunity, with m values approaching unity. These results point to a strong role for dispersal as opposed to local population dynamics in assembling forest lepidopteran communities.

Key words: community dynamics, temperate forest, Lepidoptera