Collaborative Research: Examining Origination, Extinction, and Recovery in Terebratulide Brachiopods: The Integration of Phylogeny, Morphometrics, and Biogeography.

San Diego State University Foundation, San Diego CA

Investigators

Abstract

Mass extinctions, or episodes of dramatically increased species mortality, have repeatedly perturbed the standing diversity of life on Earth. Although there is a good idea of the general effect such perturbations have had on taxonomic diversity, there are relatively poor ideas of several other dimensions of these perturbations, such as the genealogical relationships and the range of variation in size and shape among taxa going extinct and those surviving, as well as taxon distribution in space (paleobiogeographic) and time (stratigraphic). PIs propose to investigate in detail one clade (organisms sharing a single common ancestor) of marine invertebrates, the brachiopod order Terebratulida, over a period of roughly 200 million years during which the clade experiences and rebounds from four distinct mass extinction episodes: end-Emsian, end-Frasnian, end-Visean, and end-Permian. PIs research will reconstruct three components of terebratulide evolutionary history, and interpret them in relation to extinction or survival at mass-extinction events. Phylogenetic relationships among early terebratulide genera (Lower Devonian through Triassic periods) will be reconstructed using primarily parsimony-based methods of phylogenetic inference. Quantitative morphometric characteristics of terebratulides before and after these mass-extinction events will be calculated and evaluated using geometric-coordinate and outline-based methods. Global paleobiogeographic patterns that accompany these changes in morphology, phylogeny, and taxonomy through time will be studied after compiling distributional data from the primary literature. Integrating the results of PIs three-part study has the potential to test the intriguing but relatively untested hypothesis that mass extinctions act as agents of macroevolution - can selection for extinction survival operate at the level of species or clades, rather than simply on individuals or populations?