PECTINIDAE ALONG THE WESTERN ATLANTIC COASTAL PLAIN: MIOCENE TO RECENT

Today, many taxa are restricted by a biogeographic boundary near Cape Hatteras, North Carolina. This study uses data from the Paleobiology Database and the Global Biodiversity Information Facility to record how diversity and latitudinal ranges in Pectinidae responded to Miocene-Recent environmental change. Data are restricted to 25°N to 40°N. We group all occurrences of Pectinidae (140 species) into 4 time bins: Miocene, Pliocene, Pleistocene, and Recent and calculate latitudinal range-endpoints and range shifts for species that occur in two time bins.

During the Miocene, most species are found at either end of the study area. Four species range through Cape Hatteras and one is restricted north of Cape Hatteras, indicating little change across the boundary. In the Pliocene, while some species are restricted both north and south of Cape Hatteras, diversity is fairly constant throughout the study area. This suggests that Cape Hatteras was not a major biogeographic boundary at this time. During the Pleistocene, most scallop diversity is concentrated in southern latitudes (mostly Florida). The presence of A. irradians north of 35°N suggests that this pattern is not due to poor sampling, and that a biogeographic boundary was established during this time interval. Today about 60% of species in the Modern have a northern range endpoint south of 35ºN. This indicates that while many species of Pectinidae expanded north, Cape Hatteras still represents a biogeographic boundary for many scallops.

When range shifts are considered, almost all species move south from the Miocene to Pliocene, consistent with greater Miocene sampling in northern areas. Almost all species move south from the Pliocene to Pleistocene, despite better Pleistocene sampling in northern areas. This is consistent with the emergence of a biogeographic boundary during the Pleistocene. In the Recent, most surviving Pleistocene species shift northwards, which is consistent with modern warming. Overall these results suggest that during this time interval, Pectinidae were greatly affected by the Plio-Pleistocene extinction, and rebounded in diversity during the Recent.