|HOME SCHEDULE AUTHOR INDEX SUBJECT INDEX|
Integrating predator-induced behavior, morphology, and life history: Why choose a single trait?
Hoverman, Jason*,1, Auld, Josh1, Marko, Adam1, Relyea, Rick1, 1 University of Pittsburgh, Pittsburgh, PA
ABSTRACT- The number of studies documenting predator-induced plasticity has grown at an amazing rate. This work has shown that prey are capable of deploying a variety of responses to predator. However, few studies have examined how prey integrate their responses to predators and how predator-induced responses are integrated across different resource levels. This experiment examined the responses of a common pond snail, Helisoma trivolvis, to two predators, crayfish (Orconectes rusticus) and giant water bugs (Belostoma flumineum), using a factorial combination of caged predator density (0, 1, or 2) crossed with food ration (2.5%, 5%, or 10% Spirulina). Over the course of the experiment we recorded habitat use (the proportion of snails at the water surface), size-independent morphological responses (six shell traits), and life history traits (size at first reproduction, number of egg masses laid, the number of eggs per egg mass, and final mass). The data showed several important results. Snails did not behaviorally respond to caged Belostoma or to the food rations by altering their use of the water surface. However, caged crayfish increased the use of surface habitats by the snails. Caged Belostoma induced the formation of longer, higher, and thinner shells but no differences in mass whereas caged crayfish induced the opposite shell traits and greater mass. Food ration significantly increased snail mass but had no effect on morphology. Analysis of the life history traits showed that higher food levels decreased time to and age at first reproduction and increased the number of egg masses and eggs per egg mass. Snails reared in the presence of predators showed increased time to first reproduction and fewer egg masses and eggs per egg mass. This study shows how prey are able to integrate their diversity of phenotypic responses according to the food and predator regime that it encounters.
Key words: trait integration, predator-induced plasticity, aquatic snails, resource level