Although many studies have shown that species richness increases from high to low latitudes (the latitudinal diversity gradient), the mechanisms responsible for generating and maintaining higher species richness in the tropics remain intensely debated. Here, we investigate how the effects of temperature on speciation rates (kinetic effects) and the effects of productivity on community size (chemical effects) explain the latitudinal diversity gradient of South American small mammals. We implemented Bayesian models that integrate processes from the neutral and metabolic theories, comparing model predictions with empirical richness patterns. The neutral-metabolic model predicted the latitudinal richness gradient in South American small mammals. We found evidence that the effects of productivity on community size are more important for explaining differences in species richness than the effects of temperature on speciation rates. These results suggest that differences in species richness along latitudinal gradients are primarily regulated by the chemical effects of productivity on speciation-extinction dynamics.

Zip archive of data files

This dataset contains all the files used to investigate how the effects of temperature on speciation rates (kinetic effects) and the effects of productivity on community size (chemical effects) explain the latitudinal diversity gradient of South American small mammals. The data includes 1) grid cell ID, latitude and longitude coordinates, annual mean temperature (temp), net primary productivity (npp), and community data (presence/absence matrix) obtained for the three groups (named files "AllData_Didelphid", "AllData_Caviomorph", "AllData_Cricetid"); 2) codes and functions used to perform the neutral-metabolic model and produce the figures presented in the manuscript (named file "Neutral_Metabolic_Model.R"); 3) a South America shapefile (named file "South_America_shapefile").