Macroecological Evidence for Competitive Regional-Scale Interactions between the Two Major Clades of Mammal Carnivores (Feliformia and Caniformia)

Geographical gradients in species diversity are often explained by environmental factors such as climate and productivity. Biotic interactions play a key role in evolutionary diversification and may therefore also affect diversity patterns, but this has rarely been assessed. Here, we investigate whether negative competitive interactions shape the diversity patterns of the two major mammalian clades of carnivores, the suborders Caniformia (dogs and allies) and Feliformia (cats and allies) within the order Carnivora. We specifically test for a negative effect of feliform species richness on caniform species richness by a natural experiment, The Great American Interchange, which due to biogeographic lineage history and climate patterns caused tropical South America to be colonized by most caniform families, but only one feliform family. To this end we used regression modelling to investigate feliform and caniform richness patterns and their determinants with emphasis on contrasting the Old and New World tropics. We find that feliform richness is elevated in the Old World Tropics, while caniform richness is elevated in the New World Tropics. Models based on environmental variables alone underpredict caniform richness and overpredict feliform richness in the New World and vice versa in the Old World. We further show that models including feliform richness as a predictor for caniform species richness significantly improve predictions at the continental scale, albeit not at finer scales. Our results are consistent with a negative effect of feliforms on regional-scale caniform diversification within the tropics, probably indicating that niche space occupancy by the one clade constrains diversification in the other in the build-up of regional faunas, while negative interactions at smaller scales may be unimportant due to niche differentiation within the regional faunas.