| The determinants of species richness and community structure are poorly understood, particularly in the remarkably diverse Neotropical fauna. Due to their abundance, trophic diversity, and importance to ecosystem functioning and as dominant members of this fauna, ants provide significant opportunities for analyzing diversity patterns. One group, the hyperdiverse and dimorphic ant genus Pheidole, consistently dominates tropical ant communities and is an ideal clade for the study of community organization and the role of social organization in ecological interaction. I investigated species richness, community structure and social organization in an Amazonian ant community, focusing on Pheidole and other litter-nesting ants. First, I examined the impact of natural disturbance - flooding - on litter-nesting ant diversity. Among a variety of environmental variables (litter depth, twig availability, canopy cover, plant density, percent soil nitrogen, carbon, and phosphorus), degree of flooding was most strongly related to ant density in flooded forest. Low-disturbance habitat was equally as species rich as terra firme after adjusting for density, while the composition of ant species varied significantly along a flooding gradient. Second, I studied the potential trade off between morphological specialization and behavioral flexibility among major workers in litter-nesting Pheidole by quantifying nursing, a caste-atypical task for majors, in natural colonies and in experimental monocaste subcolonies. Majors were significantly less efficacious than minors at caring for brood, suggesting that morphology may reduce flexibility in the genus. However, there was no correlation between degree of morphological specialization and brood growth or survival across species. Third, I investigated ecological and behavioral differentiation in a community of 59 Pheidole species. Species differed strongly in size, abundance, tolerance to flooding, nest site usage, foraging range, and resource dominance, but not in daily activity or resource discovery rate. A molecular phylogenetic analysis indicated ancient divergence for most species in the analysis. Ecologically induced differentiation appears to have been important in generating species with distinct suites of behavioral traits. Overall, my study represents the first investigation of the community structure and behavior of diverse tropical Pheidole. My results offer insight into the causes of hyperdiversity in Pheidole, a dominant faunal group in Neotropical ecosystems. |
