PREY-SIZE SELECTIVITY IN THE BIVALVE CHIONE IN THE FLORIDA PLIOCENE-PLEISTOCENE: A REEVALUATION

Previous study of drilling predation on the bivalve Chione during the late Neogene of Florida suggested that prey-size selectivity of predators was disrupted by species turnover and morphological change within the prey genus. More recent experimental work, however, showed that at least some of these changes can be attributed to the confounding effects of facies shifts between naticid-dominated, muricid-dominated, and mixed predator assemblages. Here, we use new criteria to isolate the muricid component of the Chione drillhole record and analyze the history of this type of predator independently. Our analysis, based on bulk collections of drilled Chione from the Florida Plio-Pleistocene and Recent, does not support the previous scenario of disruption at the end of the Pliocene followed by predator recovery. Rather, selected prey size has steadily increased since the middle Pliocene, although the stereotypy of prey-size selection behaviors has decreased. We discuss these trends in light of the long-term increase in the abundance of Chione prey in molluscan bulk samples from the same time intervals.