SOTKA, E.E.; College of Charleston: The evolution of herbivore offense in the sea: tropical versus temperate herbivores in feeding tolerance for chemically-rich seaweeds

The past 25 years of research on seaweed-herbivore interactions have witnessed remarkable advances in our understanding of seaweed defenses, the chemical and morphological mechanisms that seaweeds use to protect themselves from being consumed by their herbivores. In contrast, we have relatively less information on herbivore offense, the traits that allow herbivores to increase their feeding rates on seaweeds when this use benefits the herbivore. This lack of information impedes our ability to predict the course and rate of the evolutionary response to perturbation to seaweed communities, including increasingly prevalent blooms of noxious or introduced seaweeds. As an example, there is a mountain of evidence that tropical seaweeds produce greater types and quantities of seaweed chemical defenses than temperate seaweeds. In contrast, there is little direct evidence on whether tropical herbivores have evolved greater feeding preferences for, and juvenile performance on, tropical seaweeds relative to temperate herbivores. I use a combination of field-sampling, laboratory rearing assays and DNA phylogeography to directly compre the genetically-based feeding responses of tropical and temperate populations toward chemically-rich tropical seaweeds. If I find that tropical populations have evolved greater feeding tolerance, then this would be consistent with the notion that tropical seaweeds and herbivores are evolving in a diffuse coevolutionary manner.