Meeting Abstract

S8-1.5  Friday, Jan. 6  Phenotypic plasticity's role in the origins of novel feeding strategies LEDON-RETTIG, C.C.*; PFENNIG, D.W.; CRESPI, E.J.; University of South Florida, Tampa; University of North Carolina, Chapel Hill; Washington State University cledonrettig@mail.usf.edu

Although environmentally dependent genetic variation could play a critical role in promoting rapid environmental transitions, few empirical studies have evaluated its presence in ecological and evolutionarily relevant traits. I assessed the role of cryptic genetic variation - variation that has no discernable phenotypic effect under typical conditions, but is exposed and amplified when a population experiences an environmental stressor - in the evolution of a novel feeding strategy among spadefoot toad larvae. Members of the genus Spea have evolved a novel suite of traits (behavioral, physiological and morphological) associated with carnivory and cannibalism. Using a comparative approach and a series of experiments, I found that exposing a species with the ancestral feeding strategy to the derived diet amplifies genetic variance in traits that are beneficial for consuming that diet. I also investigated a mechanism for the expression of cryptic genetic variation. Corticosterone (CORT), the major vertebrate stress hormone, is upregulated in response to novel or suboptimal conditions. Further, CORT is known to mediate physiological, developmental and morphological plasticity. By using hormonal manipulations, I determined that diet-induced CORT might be responsible, in part, for the expression of cryptic genetic variation in this ancestral lineage. This suggests that vertebrate hormones not only play a role in mediating developmental transitions and physiological trade-offs at an individual level, but might also mediate the expression of population genetic variation during environmental transitions.