WATKINS, T.B.*; MCPEEK, M.A.; Macalester College, St. Paul, MN; Dartmouth College, Hanover, NH: Quantitative Genetics and the Foraging/Predation Risk Trade-Off in Green Frog Tadpoles

Evolutionary genetic studies often examine traits that are ecologically important in that they are subject to selection in the wild. But when those traits are also responsible for shaping the distribution of a species, then a genetic analysis can provide insight into the evolution of community structure, range expansion, invasibility, etc. We performed a quantitative genetic analysis of traits related to the common trade-off between foraging gains and predation risk in green frog tadpoles (Rana clamitans). This trade-off is largely responsible for determining the distribution of the species. Burst speed, growth rate, size, and shape were significantly heritable but swimming activity in the presence and absence of predator odors was not. These heritability estimates agree with known and expected patterns of selection in green frogs. There were positive phenotypic correlations among activity measurements, and between growth rate and shape. The only significant genetic correlations were between growth rate and size, and between burst speed and shape. Growth rate was not correlated with any measure of predator avoidance or escape ability, which is counter to our expectation based on a trade-off between predation risk and foraging gains. Our results indicate that trait correlations observed among species are not simply mirrored at the intraspecific level. Given the importance of the foraging/predation risk trade-off to this species’ distribution, our results identify specific constraints on the ability of green frogs to expand into new habitats. Supported by NSF DEB-9806293.