59.2 Tuesday, Jan. 6 Specialist and generalist herbivores regulate food intake on diets containing novel plant compounds TORREGROSSA, A-M*; AZZARA, A. V.; DEARING, M.D.; University of Utah, Salt Lake City, UT; University of Utah, Salt Lake City, UT; Bristol Myers Squibb, Princeton, NJ email@example.com
Specialist herbivores are predicted to have evolved biotransformation pathways that can process large doses of the preferred plants secondary compounds (PSCs), however, specialization is thought to limit an herbivores ability to ingest novel PSCs. In contrast, generalists are predicted to regulate intake of PSCs by alternating the plants that they consume thereby decreasing the possibility of over-ingestion of any particular PSC. Because generalists ingest a mixed diet, it has been hypothesized that generalist herbivores would be better able to maintain body mass on a diet containing a novel toxin than specialists. We further hypothesized that both species would regulate toxin intake by decreasing meal size in a dose dependent manner. We tested these hypotheses by comparing the feeding behavior of two herbivorous rodents: a juniper specialist, Neotoma stephensi, and a generalist, N. albigula on a novel PSC diet of phenolic resin from creosote (Larrea tridentata). Animals were fed diets with increasing resin concentrations (0-4%) for three days per concentration. Animals that lost more than 10% of starting body mass were removed from the trial. Specialists were significantly more likely to be removed from the trial (5 of 12) than generalists (1 of 11). In addition, although the specialist and generalist both regulated phenolic resin intake via meal size on the 4% diet, only the generalist showed regulation on the 2% diet. The ability of the generalist to regulate at a lower concentration may provide an advantage over the specialist. These data provide evidence for the hypothesis that the foraging strategy of specialists results in a trade off in the ability to consume novel PSCs.