THE EFFECTS OF GEOGRAPHIC RANGE SIZE ON PATTERNS OF EXTINCTION RECOVERY ACROSS THE K-PG BOUNDARY

The Cretaceous-Paleogene (K-Pg) extinction is the most recent of the five major mass extinctions, the aftermath of which saw many groups that dominate the Earth today rise to prominence. Therefore, it is important to understand the mechanisms that contribute to survivorship of this event and post-extinction diversification. Geographic range size is commonly cited as an emergent property that enhances survivorship, where having a larger geographic range size reduces extinction potential even during mass extinctions. More rarely, however, are factors that promote survivorship also analyzed with respect to the potential for post-extinction diversification. Here, we test if there is a relationship between pre-extinction geographic range size and post-extinction genus richness in mollusk families across the K-Pg boundary. The PaleoBiology Database (PBDB) was used to collect global occurrences of gastropods and bivalves ranging from the Maastrichtian through the late Paleocene, and data were sample standardized. Family-level geographic range in the Maastrichtian was calculated using both maximum latitudinal extent and maximum great circle distance. These measures were paired with estimates of within family genus richness in the Maastrichtian and compared to changes in this metric in the Paleocene. Preliminary results suggest that there is a positive correlation between familial range size and genus richness in the Maastrichtian, as well as a lower proportion of generic extinction in broadly distributed families. Notably, greater range size is also positively correlated with post-extinction generic richness. These results demonstrate that geographic range size not only reduces extinction potential, but also may influence post-extinction diversification. Seeking this pattern in additional extinction events will demonstrate the degree to which biogeographic patterns influence both extinction and radiation dynamics generally. Such a pattern may help inform future conservation efforts by providing insight not only into which taxa most vulnerable to extinction, but also those with the greatest recovery potential.