Environmental Correlates of Community Structure in Living and Fossil Cercopithecid Primates

Cercopithecid primates today occupy the greatest geographic and climatic range of any non-human primate group. Pliocene and Pleistocene cercopithecids are often found together in fossil deposits across East and South Africa, raising the question of how these species co-occurred with one another and survived in increasingly arid and seasonal environments. Aspects of shearing ability, molar enamel thickness, and relative incisor, premolar, and molar proportions were analyzed in principal component analysis and used to generate six potential models of the cercopithecid dental morphological niche. Resulting principal component axes distinguish between taxa with varying proportions of leaves, fruit, insects, and seeds in the diet, but lose some clarity when variable subsets are used that exclude poorly-preserved or wear-restricted variables. Resampling was used to reconstruct the aggregate dental morphological niches of cercopithecid communities (taxocenes) from Africa and Asia today and from the African Pliocene and Pleistocene. Modern Asian cercopithecid taxocenes occupy a more restricted niche than their counterparts in Africa, but in both regions variation in taxocene structure is linked with past and current climate factors related to precipitation, temperature, and seasonality. Fossil cercopithecids from the Turkana Basin occupy an expanded niche in comparison to modern African and Asian taxocenes. In contrast, South African fossil taxocenes occupy a more distinct and restricted niche, which may reflect a mix of paleoenvironmental and taphonomic factors. Overall these results are consistent with existing research on modern African and Asian primate taxocene diversity and highlight the utility of a dental metric model for examining community evolution among Plio-Pleistocene cercopithecids in Africa. Evidence for a possible niche expansion during the early Pleistocene coincides with a period of well-documented hominin co-occurrence at the same fossil sites, suggesting that these two primate groups were diversifying in response to shared environmental stimuli.