Paper No. 10
Presentation Time: 10:45 AM
BIOGEOGRAPHIC RESPONSES OF MOLLUSK SPECIES TO PLIO-PLEISTOCENE ENVIRONMENTAL CHANGE IN THE WESTERN ATLANTIC
Plio-Pleistocene mollusk species from the southeastern United States have an outstanding fossil record and have been intensively studied by paleontologists for over 150 years. Recent attention has focused on the responses of these mollusks to regional environmental changes during the Plio-Pleistocene that resulted from the closure of the Central American Seaway and the onset of northern hemisphere glaciation. Of particular interest has been the magnitude and timing of faunal extinction and turnover in relation to these events. The relationship between these environmental changes and the biogeography of the species themselves—especially across multiple time slices—however, remains less thoroughly studied within this system. Further elucidation of this relationship would help to clarify our understanding of the evolutionary dynamics of these species over geological time scales, which cannot be fully characterized by tabulation of extinction and origination rates alone.
Here we use a new dataset derived from the extensive Invertebrate Paleontology collections of the Florida Museum of Natural History to quantitatively evaluate biogeographic patterns in over 90 species of gastropod (four families) and bivalve (three families) mollusks. Our dataset contains over 12,000 georeferenced occurrence records assigned to five geographically-standardized time slices (Late Pliocene to recent). In particular, we assess range size stability of individual species over time in the face of major environmental change and compare patterns of range contraction (or lack thereof) amongst species in the time interval preceding their extinction. These analyses broadly address the question of how environmental change affects the geographic ranges of species, which is one of the most important determinants of extinction resistance in marine invertebrates.