Predators and dangerous prey in the fossil record: Evolution of the busyconine whelk-Mercenaria predator-prey system

I examined the interaction between shell-chipping busyconine whelks and their hard-shelled bivalve prey Mercenaria to evaluate whether coevolution (reciprocal adaptation) between predator and prey was an important process shaping the evolution of the interaction. Prey in this interaction have been hypothesized to be “dangerous” because they are able to inflict injury to the predator; whelks often break their own shell while chipping open prey. Feeding-induced damage may lead to decreased growth, reproduction, and increased vulnerability to size-dependent predators for whelks. Experimental results indicate that interaction with Mercenaria has strong highly significant and predictable selective consequences for Sinistrofulgur , suggesting that evolutionary response of the predator to prey adaptation is likely in this system.; Evaluation of the fossil record of unsuccessful whelk predation traces suggests that chipping behavior evolved in the Busycon-Sinistrofulgur clade in the early late Pliocene, which constrains tests of coevolution to the Pliocene to Recent. Temporal trends in frequencies of successful and unsuccessful whelk predation traces on Mercenaria suggest predation intensity, and the likelihood of prey adaptation in response to whelk predation, increased through the Plio-Pleistocene record of the interaction. Mercenaria evolutionary size increase is best explained as coevolutionary response to the increased hazard of whelk predation. Temporal trends in decreased prey effectiveness (ratio of unsuccessful to total predation attempts) and increase in minimum boundary of a size refuge from predation suggest improvement of whelk prey capture capabilities. Sinistrofulgur evolutionary size increase is best explained as coevolutionary response to prey adaptation; coevolution also best explains temporal behavior-related changes in whelks that led to a decrease in frequency of chipping-induced damage to the predator when encounters with damage-inducing prey occur.