Interaction intensity as determinant of geographic range overlap between ant-following birds and army ants

Abstract

Biogeography has as a central theme, which is the study of geographic ranges of species that are determined by evolutionary history, abiotic factors, and biotic interactions. Understanding the influence of biotic interactions on geographic ranges is a topic that has been little explored, especially in a way that compares species that vary in intensity of interaction. Here, we assessed interaction intensity as a determinant of geographic range overlap between ant-following birds and army ants in Mexico and Central America. We hypothesized that the intensity of the interaction between army ants and ant-following birds, obligate or facultative, predicts the overlap of geographic ranges of interacting species, as well as the extension of geographic ranges. We generated species distribution models with MAXENT and estimated the percentage of overlap between two species of army ants and 10 species of ant-following birds. Contrary to our predictions, Bayesian regression models found no support for an estimated higher range overlap for obligate ant-following birds and army ants, or wider geographic ranges for facultative ant-following bird species. However, our results suggested trends for higher percentages of range overlap between obligate ant-following birds and army ants, and for geographic ranges of facultative ant-following birds extending to areas without the presence of army ants. Our research encourages further exploration of the biogeography of biotic interactions as part of a quantitative gradient of intensities and not as qualitative categories, integrating spatial and temporal variation in the intensity of interaction.