Ecological differentiation among key plant mutualists from a cryptic ant guild

As key dispersers of herbaceous seeds, Aphaenogaster ants strongly influence the distribution of woodland plants in eastern North America. Ants within this genus are difficult to distinguish and often are identified by subgroup, but emerging research suggests they occupy species-specific ecological niches. As such, distinct climatic requirements among Aphaenogaster spp. might result in transient plant interactions with climate change. We examine whether there are ecological and distributional differences among Aphaenogaster species that coincide with current taxonomic differentiations. We use occurrence records for six Aphaenogaster spp. that occur in deciduous forests in eastern North America. We associate the geographic patterning of species occurrence with temperature and precipitation data, and we examine whether unique climatic niches characterize each species. We then predict habitat suitability throughout eastern North America using species distribution models. For verification, we test how well the predicted ranges fit observed occurrences using novel data sets for each species. We find that Aphaenogaster species within this cryptic genus demonstrate unique ecological and geographic signatures. Each species within the subgroup generally responds differently to temperature, and somewhat differently to precipitation and seasonal variance, suggesting unique ecological niches for each species. Our results indicate that each ant species may respond uniquely to changes in climate. Such shifts could disrupt current community associations and biotic interactions with ant-dispersed plants.