Unique functional diversity during early Cenozoic mammal radiation of North America

Mammals influence nearly all aspects of energy flow and habitat structure
in modern terrestrial ecosystems. However, anthropogenic effects likely
have altered mammalian community structure, raising the question of how
past perturbations have done so. We use functional diversity to describe
how the structure of North American mammal communities changes over the
past 66 Ma, an interval spanning the rebound radiation following the K/Pg
and several subsequent environmental disruptions including the PETM, the
expansion of grassland, and the onset of Pleistocene glaciation. For 264
fossil communities, we examine three aspects of ecological function:
functional evenness, functional richness, and functional divergence.
Shifts in functional diversity are significantly related to major
ecological and environmental transitions. All three measures of functional
diversity increase immediately following the extinction of the non-avian
dinosaurs, suggesting that high degrees of ecological disturbance can lead
to synchronous responses both locally and continentally. Otherwise, the
components of functional diversity respond differently to environmental
changes and are decoupled for the last ~56 million years.