Ant coexistence in a spatially heterogeneous region in central Florida

In this dissertation I examine how spatial and environmental context alter the processes promoting coexistence among ant species spanning a spatially heterogeneous region in Florida. At the regional scale, ants partition between shrub and forest habitats. This observed spatial partitioning likely results from a process of environmental filtering; I provide initial evidence for links between the physiological and morphological traits of ants and their distributions along environmental gradients. Thus trait variation among ants interacts with environmental heterogeneity to supplement ant coexistence at the regional scale. At the local scale, I analyzed evidence for species segregation along spatial, temporal, and dietary axes. No evidence was found for spatial partitioning of ant foraging ranges. However, ants exploit the comparatively pronounced thermal gradient in shrub habitat and the comparatively wide food resource base in forest habitat. A dominance-thermal tolerance trade-off promotes local coexistence in shrub habitat, by enforcing temporal partitioning, while comparatively strong trophic differentiation reduces food use overlap in forest habitat. Thus the processes determining ant species coexistence are contingent on both spatial scale and environmental context. However, niche-based processes, as described in this thesis, may not fully account for high biodiversity. Future work examining whether neutral processes act within the groups of ecologically similar species delimited in this dissertation may resolve whether niche and neutral processes interact to maintain high ant biodiversity.