Species should only persist in local communities if they have functional traits that are compatible with habitat-speciWc environmental conditions. Consequently, pronounced regional environmental gradients should produce environmental Wltering, or a trait-based spatial segregation of species. It is critical to quantify the links between species' functional traits and their environment in order to reveal the relative importance of this process to community assembly and promote understanding of the impacts of ongoing environmental changes. We investigated this relationship using epigaeic ants in an environmentally heterogeneous region of Florida. We found evidence for environmental Wltering as environmental conditions such as groundcover, surface temperature, vapor pressure deWcit, and plant diversity were strongly correlated with assemblage composition. Certain species traits appeared particularly important to persistence: (1) ants in environments with less groundcover have relatively longer legs but do not diVer in size, (2) ants in hotter environments exhibit greater thermal tolerances, and (3) ants in hotter and drier environments do not exhibit greater desiccation resistance. These Wndings show surface complexity and temperature may interact with morphology and physiology to impact the spatial distribution of ants and underscore the importance of climate change. Climate warming is predicted to alter assemblage composition, competitive dynamics, and consequently impact ecosystem processes. We suggest environmental Wlters acting at regional scales, as shown here, act in tandem with more frequently studied local-scale competitive interactions to delimit ant community assemblages.

1. Ecological trade-offs in ant (Hymenoptera: Formicidae) assemblages and their implications for coexistence boast a rich history in entomology. Yet investigations of trade-offs have largely been limited to homogeneous environments. We examined how environmental context modifies trade-off expression in an ant assemblage spanning a heterogeneous region in central Florida, U.S.A.2. We examined how trade-off expression is altered among two contrasting habitat types: open shrub and forest. We tested for the presence of the dominance-discovery trade-off and two dominance-thermal tolerance trade-offs by estimating behavioral dominance, discovery ability, and thermal tolerance (foraging thermal limit, lethal temperature, and maximal abundance temperature) for a wide range of interacting ant species.3. We found significantly linear dominance hierarchies in both shrub and forest habitats, showing dominant species out-compete subordinates for food resources. In thermally stressful shrub habitats, subordinates exhibit higher thermal tolerances, take greater thermal risks, and reach maximum forager abundances at higher temperatures than do dominant species. This suggests temperature mediated trade-offs control coexistence in shrub habitat. In thermally moderate forest habitat, we found limited evidence for trade-offs between competitive dominance and resource discovery or between dominance and thermal traits, implying other processes control coexistence. These results demonstrate that trade-offs controlling ant coexistence may be contingent on environmental context.