March 6 2017

11:00 1100 TLSB

Jonathan Marcot
Department of Animal Biology
University of Illinois at Urbana-Champaign

Environmental Change and Mammalian Evolution: Case Studies from the Fossil Record


Throughout the Cenozoic, Earths climate and environments have changed substantially. Organisms are expected to show a variety of possible responses to these changes over a range of time and spatial scales. This presentation will highlight some recent and ongoing research on the phenotypic evolution, changes in ecological structure and biogeographic patterns of North American mammals over the past 55 million years, in the context of environmental changes during that interval. One significant environmental change was the origin of grass-dominated ecosystems over the past 25 million years. This new ecosystem induced conspicuous changes to the craniodental morphology of many ungulates, but the influence on the limb skeleton has received less attention. This study shows that shifts in the rates and patterns of limb evolution of horses generally pre-date the earliest evidence of grass-dominated ecosystems, indicating that expansion of open environments might have preceded the ecological expansion of grasses. A dramatic change in the evolution and ecology of ungulate body mass coincides with a rapid cooling event at the Eocene/Oligocene boundary \(34Ma\), suggesting fundamentally different conditions after that climatic event. Finally, the analysis of fossil mammal collections throughout the Cenozoic shows that the mammalian latitudinal diversity gradient that is nearly ubiquitous today only took its modern form the past 4Ma, and was likely absent for much of the Cenozoic. Results of this, and other studies from my lab, confirm a complex but direct influence of environmental change on mammalian evolution and ecology.











































































































































































































































































































































































































































































































































































































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