Andrew Michael Durso

Colonization of new habitats exposes populations to novel selective pressures, and the evolutionary dynamics of invasive species are determined by how the founding environment interacts with the phenotypes of invaders. Measuring these processes depends on measuring natural selection immediately upon colonization, which has been a logistical hurdle for understanding how selection operates in newly established populations. We established six brown anole (Anolis sagrei) populations on spoil islands in Florida and manipulated initial sex ratios to understand how natural selection differs based on the composition of founding populations. We found unpredictable spatial and temporal variance in natural selection, and selection increased in strength over time and with increasing adult density. The relationship between phenotypes and fitness in newly established populations may not be consistent over time. As a result, each colonization event by an invasive population provides the opportunity for a novel evolutionary trajectory towards either establishment or extirpation.

Warning coloration and Batesian mimicry are classic examples of Darwinian evolution, but empirical evolutionary patterns are often paradoxical. We test whether a new factor, trade-offs with foraging, influences the evolution of striking coloration by integrating genetic and ecological data for aposematic and mimetic snakes (Elapidae and Dipsadidae). Our phylogenetic comparison of a total of 432 species demonstrated that dramatic changes in coloration were well-predicted by the foraging strategy. Multiple tests consistently indicated that warning coloration and conspicuous mimicry were more likely to evolve in species where foraging costs of conspicuous appearance were relaxed by the poor vision of their prey or concealed habitat. Reversion to crypsis was also well-predicted by ecology for elapids, but not for dipsadids. In contrast to a theoretical prediction and general trends, snakes’ conspicuous coloration was correlated with secretive ecology, suggesting that a selection regime underlies evolutionary patterns. We also found evidence that mimicry of inconspicuous models (pitvipers) may have evolved in association with foraging demand for crypsis. These findings demonstrate that foraging is an important factor necessary to understand the evolution, persistence, and diversity of warning coloration and mimicry of snakes, highlighting the significance of additional selective factors in solving the warning coloration paradox.