MOLLUSCAN DIVERSITY AND TROPHIC STRUCTURE IN TIME AND SPACE: DYNAMICS OF THE REPUTED PLIO-PLEISTOCENE EXTINCTION IN THE CAROLINAS
The reputed mass extinction apparently had relatively little impact on richness and trophic structure prior to the upper Waccamaw and correlative upper James City; some geographic differences occur. Samples from the Neuse River northward are less diverse than the southern Duplin and Waccamaw sites. The Pliocene Duplin on the Lumber River is our most diverse sample (57 bivalve, 24 gastropod genera) but 95% confidence intervals (CI) overlap with several Pleistocene lower Waccamaw sites; less diverse Duplin and lower Waccamaw samples also overlap. Upper Waccamaw bivalve assemblages are significantly less rich (37 genera); the least rich gastropod sample (8 genera at Todd Pit) is also upper Waccamaw. Chowan River and lower James City (Pleistocene) bivalve samples are significantly less rich (36 genera) than Duplin and lower Waccamaw samples and overlap in 95% CI with the upper Waccamaw. The upper James City is the least rich bivalve sample (26 genera) and one of the least rich gastropod samples (16 genera) but all northern gastropod samples overlap in 95% CI. Fewer geographic differences occur in trophic structure. Suspension feeders consistently make up ~75% of bivalve genera across all formations. However, fewer predatory gastropods occur in the northerly samples and in the upper Waccamaw.