Ant impacts on global patterns of bird elevational diversity

Using data on bird species elevational distributions from all of the world’s mountain ranges, bird diets, and the distribution of the ant genus Oecophylla, we show that global patterns in bird elevational diversity are likely to be affected by competition with ants. Oecophylla is an abundant and effective predator of invertebrates, preying on the same species that invertivorous birds feed on. In mountain ranges with Oecophylla present in the foothills, maximum species richness of invertivorous birds occurs, on average, at 960m, ~450m higher than in mountain ranges without Oecophylla to produce a mid-elevation peak in bird species richness. Where Oecophylla is absent, bird species richness shows monotonic declines with increasing elevation. Oecophylla likely reduces prey density for invertivorous birds, low prey abundance reduces invertivorous bird density which in turn is correlated with lower bird species richness. The findings emphasize that competitive interactions between distantly related taxa can set range limits.

Methods
These data were obtained from the following sources: https://www.nature.com/articles/nature25794 (DOI: https://doi.org/10.1038/nature25794), and https://www.science.org/doi/10.1126/science.abl7242 (DOI: 10.1126/science.abl7242).

They were processed using the statistical and programming language R. The processed data has been uploaded to Dryad.