Andrew Zaffos presents Global Tectonics and Marine Animal Diversity

Abstract:  James Valentine proposed two seminal paleobiological hypotheses in 1970. First, he argued that global biodiversity, the total number of unique species, increases when continents are farther apart and decreases when continents move closer together. Second, in a separate paper, he proposed that global biodiversity began to exponentially increase during the Middle Mesozoic (~200 Ma). Putting those two ideas together, he further surmised that the breakup of the supercontinent Pangaea was at least partly responsible for this explosive growth. His first proposition was widely accepted by the scientific community because it made intuitive sense, but it was untestable with the data available at the time. In contrast, his second proposition, exponential growth, was and continues to be heavily debated despite a wealth of data. Our study was the first to quantitatively test the first proposition. In a modification of the original hypothesis, we found that while the separation of continents promotes increasing marine biodiversity, the collision of continents does not cause biodiversity to fall. Instead, continental collision causes diversity to plateau. This implies that Valentine was partially correct in arguing for exponential growth of diversity over time, but only when continents are fragmenting. Because we are currently entering a new period of continental collision, we should see long-term stabilization of global marine biodiversity. Furthermore, if we lose many species to extinction in the near future, the global ecosystem is unlikely to recover to current levels of diversity until the next period of net continental separation.

Bio:  Andrew Zaffos is senior research scientist at the Arizona Geological Survey and University of Arizona. His primary interest is the extinction and diversification of marine organisms. Specifically, he studies how patterns of marine deposition and erosion controlled fossil biodiversity throughout the history of complex animal life. He also studies the phenomena of niche conservatism and biogeographic conservatism in ancient marine biotas, at both regional and global scales. He is currently part of several geoinformatics initiatives - the Macrostrat Database, Paleobiology Database, the Rockd and Flyover Country social media applications, and the GeoDeepDive Library of machine-readable scientific documents - which are all working to increase the accessibility of geoscience data for the scientific community and general public.

Andrew received a B.A. in Economics from the College of William and Mary. He then saw the light and switched to the geological sciences. He received an M.S. in Geology at the University of Georgia, a Ph.D. from the University of Cincinnati, and was a postdoctoral fellow the University of Wisconsin in Madison.