RANGE AND CHANGE: THE ROLE OF CHANGING OCCUPANCY IN PREDICTING EXTINCTION RISK

Numerous analyses have shown that geographic range or occupancy of taxa is a major determinant of their extinction risk, both in deep time and today. Species and genera with relatively restricted ranges in a time interval are at a significantly greater risk of extinction than taxa with broader ranges. A pending issue is the role of changing geographic range as a determinant of extinction risk. While standing range can be confidentially identified for extant species, assessing the change of range requires historical or prehistorical data.

Here we demonstrate, based on the Phanerozoic fossil record of marine genera in general and of Cenozoic marine species in particular, that both occupancy and its temporal change are significant determinants of extinction risk. We apply a novel approach to measure changes in occupancy, based on the proportion of paired, equal-area geographic grid cells occupied by each species. The significant role of change renders paleobiological data especially valuable for determining the future fate of extant species. We use generalized linear modeling on extinct species to measure the additive and interacting effects of occupancy and its temporal change on extinction risk. Applying this model to extant marine species, we predict the probability of extinction for each species in the current temporal bin (late Pleistocene/Holocene). While climate change and anthropogenic stressors are not incorporated in the model, it may nevertheless inform conservation biology on the latent extinction risk of species with declining occupancy over longer stretches of geological time.