Origins and circumstances of adaptive divergence in whelk feeding behavior

Abstract

The late Oligocene/early Miocene to Recent fossil record of whelk predation on species of the venerid bivalve genus Mercenaria was evaluated to trace the history of specialization in feeding behavior within the predatory gastropod subfamily Busyconinae. Today, whelk species either employ a wedging or chipping mode of predation when feeding on their bivalve prey. Whelk chipping predation leaves a characteristic trace on the shell of Mercenaria. The temporal distribution of successful and failed whelk predation traces on the shell of Mercenaria suggests two independent origins of chipping behavior within the group. The behavior first evolved in the late Miocene Busycotypus species complex, but was likely lost evolutionarily due to the extinction of the whelk lineage responsible for the traces at the end of the Miocene. The behavior evolved independently in the Busycon-Sinistrofulgur clade during the late Pliocene. Circumstances that may have contributed to ecological diversification and specialization in the Busyconinae are complex. The evolution of chipping behavior is associated with times of high productivity and ecological complexity during the late Miocene and Pliocene in the western Atlantic.