Herbivores must combat the chemical arsenal of their host plants in order to feed. Our understanding of such resistance is incomplete. In North Carolina, a small (1cm) marine herbivore (the shrimp-like Ampithoe) performs well on Dictyota, a brown seaweed containing alcohols toxic to other herbivores. Ampithoe's geographic range is larger than the plants', and previous work shows populations which are outside Dictyota's range do not perform as well as populations within Dictyota's range. The proposed research will identify plant compounds responsible for mediating these differences in performance. This will allow the identification of biochemical resistance mechanisms that respond to the toxins. These known host use patterns will be placed into a within-species phylogenetic framework using DNA sequence data. The work will serve as an example for other plant-herbivore systems whose host-use is known and recent evolutionary history is unknown. One can test theory largely developed for terrestrial insect pests using an ecologically similar herbivore from a very different environment (i.e., marine vs. terrestrial) and evolutionary history (i.e., Crustacea vs. Insecta). Such tests can lead to alternatives to current theory and a more complete understanding of how herbivores may respond to plants over ecological and evolutionary timescales.
