Prominent events in the abiotic environment – such as tectonic activity, climate change, and environmental transitions – have been shown to influence biodiversity patterns globally and throughout time. The Cenozoic record of eastern Africa is no exception, with large-bodied (>5 kg) mammals exhibiting faunal turnover in association with land mass configuration and the expansion of C4 grasslands. However, the response of small mammals, such as rodents, to these abiotic transitions is often understudied – and therefore not well understood – in these records. Today and in the fossil record, eastern African rodents are a taxonomically, ecologically, and morphologically diverse group. Characterizing when and how patterns of eastern African rodent diversity were shaped by regional to global environmental changes could provide novel insights for the region’s paleoecology.

Our project synthesizes the rodent fossil record of eastern Africa, quantifying per-capita diversification rates to highlight periods of origination, extinction, and turnover in relation to paleoenvironmental, climatic, and landscape conditions. Using bootstrapping approaches, the record exhibits significantly increased extinction rates during the early-to-middle Miocene, followed by increased origination rates from the middle-to-late Miocene. We observe no shared genera between the early Miocene and late-Miocene-to-present fossil assemblages, with few familial lineages persisting through this interval. The temporal lag between extinction and origination peaks suggests that late Miocene species may not have contributed to the decline of early Miocene fauna, and implicates causal factors other than direct competition in this turnover event. We apply correlation analyses to evaluate associations between rates of rodent diversification and their hypothesized drivers in the geological and climatological records. We find significant relationships (p < 0.05) between genus-level richness and both global temperature and regional leaf wax δ13C values. However, no significant relationships were found between these environmental factors and rates of origination, extinction, or turnover. Diversity patterns are also influenced by fossil sampling, particularly during the middle Miocene turnover interval, when the fossil record is relatively sparse. To test for preservation effects in the eastern African rodent fossil record, we evaluate the relationships between richness and diversification rates with the number of localities per time bin, finding significant correlations (p < 0.001) between these factors. These results provide new insights into faunal responses to paleoenvironmental dynamics in eastern Africa through the lens of small-mammal paleoecology.