To shed light upon the drivers and dynamics of change in faunal biodiversity over time, it is important to examine that biodiversity multidimensionally. Dimensions of biodiversity include taxonomic (TD), phylogenetic (PD), and functional diversity (FD), as well as ecometrics, which quantifies the relationship between species’ traits and environmental conditions. To date, the comparative trends and responses of these dimensions to climatic and anthropogenic change over millions of years is unclear. The aim of this study was to test the hypothesis that they display unique trends over time. We obtained occurrence data of 349 herbivore species at fossil sites across Africa, representing 7 to 0 Mya. We then obtained the body mass and dental traits, phylogeny, and paleoclimates associated with each species. At each of periodic time slices, we corrected for sampling bias and calculated TD as species richness; PD as the sum of phylogenetic branch lengths connecting species; FD using species’ trait values for descriptive statistics of each trait and the 3D volume of all traits; and ecometrics as the anomalies between actual climate and the maximum likelihood of climate for different trait values. We performed LOESS regression to visualize trends in these calculations and equated trends with historical events.
Results/Conclusions
We found highly distinct temporal patterns across all dimensions of biodiversity. TD doubled from ~40 to ~120 species until Homo erectus emerged ~2.2 Mya and has since declined. PD’s consistent increase from ~55 to ~95 branch length units plateaued slightly following a rise in grasses ~4.6 Mya. For FD, species’ body masses declined dramatically after the emergence of Homo erectus, while their dental traits, namely hypsodonty index (HYP) and loph count (LOP), increased considerably after the rise in grasses. Further, FD’s 3D volume began declining immediately before 4.6 Mya, decreasing from ~5 to ~3 cubic units. Finally, ecometric anomalies associated with all three of body size, HYP, and LOP generally remained steadily at 0 across the entire time series. These results suggest that both climate and anthropogenic events may have impacted African herbivore biodiversity: the rise in grasses may have favored clades that have teeth capable of shearing tougher vegetation, and Homo erectus may have hunted large-bodied herbivores to extinction. Because reaching this conclusion was made possible by incorporating multiple dimensions of biodiversity, future biodiversity research should also consider these dimensions. This study demonstrates the power of integrating datasets from multiple sources to advance our understanding of the natural world.