Dr. Matthew Powell, Juniata College, will be speaking at the weekly Geoscience Seminar over the lunch hour on October 15, 2010, on his research into biological diversity throughout Earth's history. All seminars are in Walsh 104 from 12:15 to 1:15 p.m.
Powell’s talk is entitled “The Peak of the Latitudinal Diversity Gradient in Living and Fossil Marine Biotas.”
The latitudinal diversity gradient is the fundamental spatial distribution of living species, and, although data are somewhat limited, a gradient seems to have been present continuously throughout the Phanerozoic Eon as well. Data for several higher taxa, including brachiopods, bivalves, crinoids, and corals, show that peak diversity tracked the region of greatest continental shelf area as it shifted through time. This may indicate either that the present-day gradient, which is commonly assumed to peak at the equator, is an ephemeral feature of the biota that does not represent normative diversity dynamics, or it may indicate a substantial geographic bias in the fossil data.
We find that peak biodiversity of living organisms currently occurs between 10-20°N, even after correcting for a Northern hemisphere sampling bias. Moreover, this peak position is a global phenomenon: it is found across habitats, higher taxa, ecological groups, and evolutionary faunas and within all sampled ocean basins and on both sides of the Atlantic and Pacific oceans.
These results, first, suggest that the fossil record is not geographically biased, and, second, indicate that the position of peak marine diversity at 10-20°N should be considered a fundamental feature of the present-day latitudinal diversity gradient and factor into hypotheses of the gradient's origin.