Dimensions of ant diversity on a small tropical island

Recent appreciation of the multidimensional nature of biodiversity has prompted biologists to examine the taxonomic, functional, and phylogenetic attributes of natural communities. Simultaneous consideration of such multiple diversity dimensions provides valuable insights into various community assembly processes. We studied the alpha and beta components of ant diversity on a simple island landscape dominated by adjacent but abiotically distinct evergreen (humid & dense canopy) and littoral (dry & sparse canopy) forest habitats. We sought to (i) describe and examine interrelationships of ant diversity dimensions, and (ii) identify potential processes structuring ant communities by comparing the diversity patterns of observed and randomly generated communities. We found that the drier littoral habitat had lower ant species richness and non-random community composition, but had similar functional diversity as evergreen forests. This result is in contrast with previous studies comparing intact and human-altered habitats that reported severe loss of ant functional diversity with reduced richness. In our study, the functional similarity between habitats was maintained because communities in littoral forests were functionally overdispersed than expected by chance. We suggest that competition and/or thermal tolerance of ants may drive overdispersion of littoral ant communities. At the small spatial scale of our island, phylogenetic diversity was a poor predictor of habitat differences despite significant phylogenetic signal in functional traits and non-random functional diversity patterns. Our work highlights the need for a broad range of studies comparing multidimensional diversity in adjacent habitats that would provide a baseline for interpreting community-level changes due to anthropogenic pressures.