Ecometrics demonstrates carnivoran community dental traits are filtered by climate

Carnivorans, with their diverse diets and unique adaptations such as the carnassial tooth, offer insights into the connections between functional traits and the climatic and environmental conditions they inhabit. They shed light on functional trait-environment relationships at the highest trophic levels across a broad range of environmental conditions. In this study, we evaluate the relationship between relative blade length (RBL) of the lower carnassial tooth, a key dietary adaptation among carnivorans for slicing and grinding food items, and climate. We propose RBL as an ecometric trait and test the hypothesis that community-level RBL is correlated with climate and mediated by environmental effects on food availability. Our findings show that communities with higher mean and broader variance of RBL are typically located in warmer and wetter climates, suggesting a relationship between carnivoran dietary diversity and climate. Conversely, communities with a lower mean and narrower variance of RBL predominantly occupy cooler, drier places. This indicates that community-level carnivoran dietary traits have the potential to serve as indicators of environmental conditions. Given the robust fossil record associated with carnivorans, we also show how RBL can be used as a proxy for reconstructing paleoclimates by examining trait change at seven sites in North America to estimate changes in temperature and precipitation over time in relation to changes in carnivoran community assembly. Understanding the nature of trait-environment relationships can help us anticipate biological impacts of ongoing environmental change and the geographic regions at the greatest risk of ecological disruption.

Methods
We conducted an ecometric analysis evaluating the communitywide trait-environmental relationship between carnivoran dietary traits (relative blade length of the carnassial tooth, RBL) and climate conditions (temperature and precipitation). RBL trait values were collected from the published literature and were also measured directly from museum specimens and published images of museum specimens. Temperature and precipitation data were available through WorldClim (BIO1 and BIO12). Carnivorans were binned into ecological communities using the geographic range data available on from the IUCN and were analyzed at 50 km-equidistant points across the terrestrial globe.