Latitudinal gradients in the ecology of New World bats

Aim
The aim was 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 from the published literature, which include 245 species, along with body mass measurements and dietary categorizations. 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
South of the Tropic of Cancer, bats exhibit sharp increases in local diversity, the abundance of frugivores and nectarivores, and mean body mass. 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 might be that they are mostly frugivores or nectarivores. Therefore, they have prospered only in regions that provide fruit and nectar year‐round. Thus, biotic interactions might be the immediate cause of the latitudinal diversity gradient in New World bats. If so, then the biogeographical break is driven by environmental factors and is not a historical artefact. These results suggest that a more nuanced consideration of latitudinal gradients will prove to be helpful when it comes to studying many taxonomic groups.