Major factors controlling diversity in Cenozoic terrestrial herbivores

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Is species diversity un-bounded or is it constrained by ecological limits? Are these limits fixed or do they fluctuate? Are these limits imposed by biotic competition, or by physical drivers (e.g. climate)? Do phenotypic innovations release ecological bounds to diversity? These are crucial aspects of evolution and macroecology that remain poorly understood. Although several neontological methods (i.e. based on molecular phylogenies) have been developed to answer these questions, they have limited power to reconstruct the dynamics of both past diversification (the balance between speciation and extinction) and phenotypic evolution. This is especially the case for extinct clades or clades with few living representatives. On the other hand, process-based approaches that use information from the fossil record but also incorporate factors potentially affecting diversity have not been available to paleontologists until very recently (e.g. 2015). I here propose to apply such analytical methods (included in the software PyRate) to analyze the rich fossil record of Cenozoic terrestrial large herbivores (Artiodactyla, Perissodactyla, Proboscidea; over 2,000 species) and to investigate the main factors controlling their diversification. I aim to test: (i) whether diversification has any bounds and (ii) whether intrinsic factors (diversity dependence, competition, predation, phenotypic innovation) have a more prevalent role in controlling diversification than extrinsic factors (climate, productivity, etc.). Importantly, in the proposed approach, diversity-dependence, competition, morphospace evolution and climate will be directly fed into diversification models and can be directly compared in a probabilistic framework. As part of the project I will develop new functionalities for PyRate that will improve our ability to investigate diversity dynamics and diversification drivers, and shed new lights on the speciation and extinction dynamics of three major mammalian clades.