Abstract
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.
Highlights
Species diversity patterns are often explained only in terms of environmental factors such as climate and habitat
Our results suggest that biogeographic history combine with biotic interactions to shape the global species richness patterns in the two main extant groups of terrestrial mammal carnivores, the suborders Caniformia and Feliformia
We found that models based on environment alone underpredict feliform species richness in the Old World tropics and overpredict it in the New World tropics, while the opposite is the case for caniform species richness
Summary
Species diversity patterns are often explained only in terms of environmental factors such as climate and habitat. Interspecies killing between Carnivora species is widespread, accounting for up to 68% of mortality in some species [6] This implies some degree of competition between the two groups where they overlap, but whether such interactions affect their current geographical diversity patterns has not been assessed. As a result, opening of the Panama land bridge provided all major terrestrial caniform groups (Mustelidae, Canidae, Procyonidae (racoons), Ursidae (bears) [3,10]) an evolutionary arena relatively free from competition with feliforms, compared to the tropical regions of the Old World. A carnivore niche space occupied, in the Old World, by the smaller feliforms such as Viverridae (civets) and Herpestidae (mongooses) which are diverse in the warmer regions of the Old World [7,8,12] and never made it across the Bering land-bridge to North America. We sought to test if a negative relationship between feliform and caniform richness distributions is only a continental-scale phenomenon reflecting evolutionary interactions in the build-up of regional faunas due to niche space occupancy or if they are repeated on smaller spatial scales, reflecting more purely ecological interactions within current regional faunas
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