HUMAN INFLUENCES ON A COEVOLUTIONARY ARMS RACE BETWEEN PREDATOR AND PREY: PRELIMINARY RESULTS

As human activities continue to transform the world's marine ecosystems through the modification of habitats, elimination of top consumers by overfishing practices, and global redistribution of species, we are increasingly reducing the productive capacity and resiliency of these systems to absorb stresses. Whether current conditions provide opportunities to nurture adaptation is emerging as an important component in the development of conservation strategies.

The long-term history of coevolving species interactions provides a unique opportunity to assess ecosystem health—defined here as a permissive environment to adaptation where energy and material resources are both available and “easy” to acquire (Vermeij, 2004)---before and after human influences on the environment. Since the Pliocene, predatory whelks (Busycon and Sinistrofulgur) have coevolved with their hard-shelled bivalve prey along the Atlantic and Gulf coasts of the U.S. Whelks use their shell lip to chip open the shell of their prey, often resulting in breakage to their own shells. Predator adaptation to hard-shelled prey contributed to temporal changes in whelk size increase and behavior to decrease performance loss (shell breakage) associated with feeding on hard-shelled prey (Dietl, 2003). If human activities have diminished the productive capacity of coastal environments, it is hypothesized that opportunities for continued adaptation of energetically costly traits (predator size) and behaviors (shell-chipping) in this species interaction should cease.

Preliminary results from samples of Pleistocene and modern whelks from North Carolina suggest that functional improvement in the coevolving arms race has not been constrained (“turned off”) by human influences on the environment. Trends in predator size and feeding behavior that began in the Pliocene continue into the Recent.