Project 1 (Reclaiming the world: recovery after mass extinctions) focuses on the first half of tetrapod evolution, developing from the Early Tetrapod Database (Benton et al. 2013). The ETD includes data on 2200 valid species from the origin of tetrapods to the expansion of dinosaurs, and a well-resolved evolutionary tree has been produced. The time span encompasses two mass extinctions, at the end of the Permian (252 Ma) and at the end of the Triassic (201 Ma), and this PDRA will explore the recovery of life, with studies on (1) disparity and diversity through time for all tetrapods; (2) evolution of body size and feed- ing mode for all major groups through the crises and after; and (3) Bayesian modelling to explore speciation dynamics of all tetrapods and the main subgroups to identify the relative waxing and waning of key groups.
Project 2 (Vertebrate morphospaces and function spaces) explores changes in morphology during the origin of dinosaurs and other key events in the evolution of amphibians and reptiles. Hitherto, PCM approaches often focused simply on body size evolution – this PDRA will also explore characters associated with feeding and locomotion. Key studies include (1) exploration of the relationships be- tween body size, locomotory mode and feeding mode across all Mesozoic archosaurs (crocodiles, pterosaurs, dinosaurs); (2) identification of times of major diversification shift, based on body size, limb, and mandible data across all Mesozoic taxa, to determine the role of sudden events on macroevolution; and (3) speciation dynamics modelling using Bayesian MCMC methods, for all archosaurs, and especially exploring how the temperature-dependent groups (turtles, crocodiles) responded to temperature change through the Mesozoic.
Project 3 (The double burst of bird expansion) focuses on bird evolution. This is a perfect example for comparing diversifications driven by key adaptation (innovation) and by mass extinction (opportunity), as birds arose in the Jurassic following major innovations for flight, and then diversified again, after the end-Cretaceous mass extinction. This PDRA will perform three studies: (1) an exploration of disparity and diversity through time for all birds in their two diversifications in terms of a suite of dietary and flight-related characters; (2) a PCM study of the evolution of body size and mandible shape across all birds, and across key subclades, to test for diversification shifts and to assess evolutionary models during recovery; and (3) a Bayesian modelling study of speciation dynamics to determine how all birds, and subgroups responded in the two diversification episodes.
Project 4 (Mammal origins, explosions, and the temperature driver) explores whether mammalian diversifications track climate or not, a much debated, classic case that tests the Red Queen and Court Jester models. After extending existing large data matrices of morphological characters and construct- ing an evolutionary tree, this PDRA will explore (1) selectivity for ecological characters across mammalian evolution, and whether any show trends such as selective increase in size; (2) speciation dynamics using Bayesian modelling approaches; and (3) morphological character distributions to resolve whether clade origins are tied to key innovations, and how the timing of such innovative characters plots against the acquisition of mammalian characters in general.
Project 5 (Filling morphospace sparingly) focuses on morphospaces generated by all the morphological data accumulated by the other PDRAs, collaborating with them initially, and pursuing particular clades in cooperation. Questions focus on appropriate models of morphological evolution (uniform or episodic; directional or not), but also how morphospace is filled: do empty area of morphospace reflect impossible or forbidden morphologies, or unfilled opportunities? This PDRA will explore (1) how morphospace fills through geological time, and comparing cladistic and landmark-type data; (2) whether morphological character evolution is uniform or episodic, directional or random; and (3) whether triggers for change are external environmental shifts or related to internal factors such as genomic control.