A morphometric discontinuity between species of the bivalve Chione during a Plio-Pleistocene extinction in Florida suggests that the Pliocene species C. erosa was replaced by the immigrant C. cancellata. Here we show that immigration of C. cancellata into the Florida ecosystem changed the dynamics of naticid predation on Chione. Chione cancellata, upon its first appearance in Florida, exhibited no greater degree of escalation than its predecessor C. erosa. The relative size of prey selected by naticid predators, however, declined significantly. Selected prey size subsequently increased during the Pleistocene and into the Recent, but C. cancellata has responded by significantly increasing relative shell thickness. These patterns of interaction provide direct evidence for the disruption of predator-prey systems by mass extinctions, and the microevolutionary escalation of anti-predatory traits.
Peter D. Roopnarine, Department of Invertebrate Zoology and Geology, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118-4599, USA.
Amy Beussink, School of Renewable Natural Resources, University of Arizona, Tucson, Arizona 85721, USA.
KEY WORDS: Predation, drilling, naticid, Chione, extinction