Paleoecological significance of coupling metrics of successful and unsuccessful shell-breaking predation: Examples using Neogene bivalve prey

Abstract

Traces of durophagous predation on molluscan prey have been used as proxies to reconstruct the nature and intensity of predator–prey interactions in both the fossil record and the modern oceans. Available metrics for the quantification of these interactions have focused either on failed/unsuccessful or successful attacks in isolation. Because predator–prey dynamics and subsequent adaptation depend on both the success as well as the failure of the predator, we propose to combine these two components to increase our ability to reconstruct the dynamics of these relationships in the past. In this study, two bivalve clades, Chione and Varicorbula, from Florida's Plio-Pleistocene fossil record are used to show how the combination of repair frequency and estimated crushing mortality serve as better constraints on interpreting changes in predator–prey interactions as compared to the more limited interpretations when these two metrics are used independently. When used in tandem, the two metrics document an overall predation intensity increase from the upper Pliocene Pinecrest Beds (upper Tamiami Formation to the overlying lower Pleistocene Caloosahatchee, and a decrease in successful attack frequency in the upper Pleistocene Bermont Formations. However, patterns were different in the upper Pleistocene Ft. Thompson Formation: successful attacks increased for Chione and decreased for Varicorbula. In detail, however, the overall dynamics for these two predator–prey systems varied, and they also changed differently throughout the studied interval.