Diversity Dynamics of Middle Paleozoic Marine Animals

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ABSTRACTDiversity Dynamics of Middle Paleozoic Marine AnimalsMichael FooteEAR-0105609The subject of diversity dynamics explores how and why the number of species in the world changes over time. This research will explore diversity dynamics with data on marine animals from the middle of the Paleozoic Era, about 440 to 350 million years ago. The species composition of fossil communities will be inventoried, and the ancient geographic and environmental setting of these communities will be determined. Using this new information as well as existing data from other sources, the times of origination and extinction of animal genera (the more inclusive taxonomic units that consist of one or more related species) will be estimated. This will allow the temporal patterns of diversity, origination, and extinction to be reconstructed, and these temporal patterns in turn will be used to assess the dynamics of diversity. When diversity increases over millions of years, does this tend to occur because the rate of production of new species has increased or because the rate of extinction of existing species has decreased? Likewise, does a decline in diversity tend to be marked by a decrease in origination or an increase in extinction? In other words, is origination or extinction more important in regulating biological diversity? Previous research shows that the style of diversity dynamics changes over the course of animal evolution, with extinction more important for about the first 300 million years of the history of animals (during the Paleozoic Era) and origination more important thereafter (during the Mesozoic and Cenozoic Eras). There are reasons to think that diversity dynamics may vary geographically and environmentally. This research will be the first to test the predictions that, as far as diversity regulation is concerned, extinction is more important in the tropics than in the temperate zones and more important in shallow-water environments than in deeper waters. In addition, it is known that shallow marine and tropical marine environments were more prevalent in the Paleozoic Era than later. The results of this research will therefore be significant in determining whether the observed, long-term temporal change in diversity dynamics may be underlain by a change in the prevalence of certain environmental and geographic settings in the marine realm.