HARPER, G. R.; University of North Carolina at Chapel Hill: Does gene flow maintain a maladaptive phenotype in a Batesian mimicry complex?

Palatable species (mimics) may resemble toxic or venomous species (models) with which they co-occur and thus gain protection from predators. This phenomenon, termed Batesian mimicry, occurs in numerous plant and animal taxa. A critical prediction of Batesian mimicry is that its benefits should break down in areas where the model is absent, because predators that do not co-occur with the model will not be under selection to recognize it, or any other species that resemble it, as dangerous. Previous research supports this prediction. Contrary to expectation, however, the distributions of many mimics extend well beyond that of their models. For instance, the range of our study species, L. t. elapsoides, extends well outside that of coral snakes despite the apparent maladaptive nature of the mimetic phenotype in those areas that lack coral snakes. Gene flow, historical and/or contemporary, could possibly maintain this maladaptive phenotype despite selection against it. To test this hypothesis, we conducted a phylogeographic analysis of L. t. elapsoides to determine the level of contemporary gene flow and uncover the demographic history of this organism. There is significant genetic structure throughout the range of this organism. Results of a number of tests seem to indicate that historical gene flow has been the primary factor in spreading the mimetic phenotype outside the range of the model.