Tropical mammal functional diversity increases with productivity but decreases with anthropogenic disturbance

A variety of factors can affect the biodiversity of tropical mammal
communities, but their relative importance and directionality remain
uncertain. Previous global investigations of mammal functional diversity
have relied on range maps instead of observational data to determine
community composition. We test the effects of species pools, habitat
heterogeneity, primary productivity and human disturbance on the
functional diversity (dispersion and richness) of mammal communities using
the largest standardized tropical forest camera trap monitoring system,
the Tropical Ecology Assessment and Monitoring (TEAM) Network. We use
occupancy values derived from the camera trap data to calculate
occupancy-weighted functional diversity and use Bayesian generalized
linear regression to determine the effects of multiple predictors. Mammal
community functional dispersion increased with primary productivity, while
functional richness decreased with human-induced local extinctions and was
significantly lower in Madagascar than other tropical regions. The
significant positive relationship between functional dispersion and
productivity was evident only when functional dispersion was weighted by
species' occupancies. Thus, observational data from standardized
monitoring can reveal the drivers of mammal communities in ways that are
not readily apparent from range map-based studies. The positive
association between occupancy-weighted functional dispersion of tropical
forest mammal communities and primary productivity suggests that unique
functional traits may be more beneficial in more productive ecosystems and
may allow species to persist at higher abundances.