Meeting Abstract
Predators can exert strong influence on prey species and entire ecosystems via induced changes in prey characteristics. According to theory, the plastic nature of these prey defenses should indicate a cost, in terms of reduced energy acquisition or altered energy allocation, to the defending prey. However, these defenses are extremely varied and, in many cases, we are uncertain how, or if, these costs manifest. Further, these costs are difficult to predict as we often have a limited or theoretical understanding of the mechanism by which defense induction is achieved. We investigated the mechanism and reproductive costs of a morphological defense in the ecologically and economically important eastern oyster Crassostrea virginica in response to crab predators. This predator-prey interaction is more complicated than was previously appreciated, as results suggest oysters shift from a mechanism prioritizing predator escape to one prioritizing predator deterrence as predation risk increases. The more energy-expensive mechanism for deterrence means this defense strategy is associated with proportionally higher reproductive costs at higher levels of predation risk. Additionally, this more elaborate mechanism helps explain the results of several other studies which seemed contradictory or difficult to explain under the assumption of a more simplistic strategy. Our results demonstrate the significance of nonconsumptive predator effects for this foundational prey species which supports a unique marine habitat. Further, they demonstrate the importance of complete defense characterization in the study of phenotypic plasticity.
