Data from: Latitudinal gradients in the ecology of New World bats
Aim: To quantify gradients in local richness levels, feeding strategies, and body mass distributions in bats and relate them to environmental variation and habitat disturbance.
Location: The New World.
Time period: Present day.
Major taxa studied: Bats.
Methods: I assembled 152 local species inventories including 245 species from the published literature, as well as body mass measurements and dietary categorisations. I quantified species richness using the Chao 1 extrapolator, obtained mean mass values for the inventories, and computed proportions of species and of individuals belonging to different feeding guilds. I reduced the dimensonality of environmental variables using factor analysis and regressed richness values upon the factor scores.
Results: Bats exhibit sharp increases in local diversity, the abundance of frugivores and nectarivores, and mean body mass south of the Tropic of Cancer. These offsets are driven by increases in the richness and abundance of the leaf-nosed bats (Phyllostomidae). Richness steeply declines near the Tropic of Capricorn, but the other variables do not trend strongly at this point. Most of the variance is explained by mean annual temperature, temperature seasonality, and precipitation. There is no direct evidence that richness is lower in disturbed landscapes.
Main conclusions: The great radiation of phyllostomids in the Neotropics has created a uniquely rich biota. The reason that phyllostomids are now absent from the northern temperate zone may be that they are mostly frugivores or nectarivores, so they have prospered only in regions that provide fruit and nectar year-round. Thus, biotic interactions may be the immediate cause of the latitudinal diversity gradient in New World bats. If so, then the biogeographic break is driven by environmental factors and is not a historical artifact. These results suggest that a more nuanced consideration of latitudinal gradients will prove to be helpful when it comes to studying many taxonomic groups.