Foote et al. 2007

Foote M, Crampton JS, Beu AG, Marshall BA, Cooper RA, Maxwell PA, Matcham I. 2007. Rise and fall of species occupancy in Cenozoic fossil mollusks. Science 318: 1131-1134.

These authors examined a large dataset of species occurences in marine / shelf fossil molluscs in New Zealand, to infer patterns of geographic range and species occupancy. These data relate to hypotheses about extinction risk associated with the size of a species’ geographic range, and the rate of decline of species in ecological to geological time scales. Occupancy was defined here as the proportion of collections in a given interval in which a given species occurs.

The majority of species studied showed a steady increase in occupancy, followed by a long decrease and eventual extinction. Other possibilities, including rapid expansion and rapid decline (truncation) were not found very often, though some species did show such patterns. These results generally support the hypothesis that large geographic ranges are associated with longer species durations and reduced extinction risk, but do not support the hypothesis that species achieve maximal geographic range shortly after speciation. Additionally, the importance of incumbancy was not supported, under which species or higher taxa survive for long periods in the face of apparently superior competitors.

The authors suggest that different processes may control occupancy over ecological versus geological time scales. Competition and dispersal may be very important over ecological scales, but geological processes such as sea-level change and tectonic activity may be more important over longer time scales.