Anole Dewlap Color Evolution
Lizards in the genus Anolis represent one of the best-studied groups of reptiles in the world. With over 400 species and high morphological variation, anoles make an excellent study system in which to test evolutionary questions. From a color perspective, they are particularly interesting because they possess a dewlap - an extendable throat fan that is often brightly-colored and used for inter- and intraspecific signaling. Despite decades of study on dewlaps, we still know relatively little about why and how certain colors and patterns have evolved. One hypothesis suggests that the light environment may play a role in dewlap color evolution, as different light conditions may be more or less favorable for communicating via a particular color. I am testing this using the Panamanian slender anole (Anolis apletophallus), a species in which some individuals have mostly white dewlaps and some have mostly orange dewlaps. In collaboration with Alison Davis Rabosky, Christian Cox, Michael Logan, Owen McMillan, and various other researchers at the Smithsonian Tropical Research Institute, I will introduce hundreds of these lizards to experimental islands with varying levels of canopy openness. I will then be able to directly measure the impact of the light environment on the fitness of lizards with different dewlap colors. |
Evolution of Coral Snake Mimicry
Coral snakes are highly venomous elapids that are often brightly-colored, and they use this coloration as a warning to potential predators that they are dangerous. In addition, many species of relatively harmless snakes have evolved similar color patterns, which allow them to deceptively signal to potential predators that they, too, are dangerous. Although the benefits of looking like a coral snake may seem obvious, biologists have largely overlooked a critical component of coral snake mimicry: behavioral mimicry. Coral snakes and their mimics engage in a number of characteristic displays when threatened, such as thrashing, burying their heads, and waving their tails. Together with Alison Davis Rabosky, Talia Moore, and collaborators from the Department of Engineering at the University of Michigan, I am working to build snake robots that can behave like coral snakes. I will produce these robots in a variety of colors and deploy them in tropical forests (where there are many species of coral snakes and mimics). This will allow me to disentangle the roles of color and behavior in the evolution of coral snake mimicry. |
Color Polymorphism in a Coral Snake Mimicry Complex
Color polymorphism, in which multiple color patterns co-occur in a population, presents a paradox in mimicry systems with aposematism - if model resemblance is beneficial, then what is the adaptive significance of multiple color morphs? Nevertheless, potential explanations for the maintenance of color polymorphism in mimicry systems include frequency-dependent selection, regulation via supergenes, sexual selection, and selection that varies over time and space. One way to test among these hypotheses is to compare mimetic and non-mimetic color traits, which may respond differently to selection. For my master's thesis, I worked with Christian Cox and Alison Davis Rabosky to study the ground snake (Sonora episcopa), a species that is polymorphic for two mimetic traits (black bands, red stripe) and two non-mimetic traits (black cap, black collar). Using analysis of spatial patterns, population genetics, and models of linkage relationships, I found that strong diversifying selection on mimetic traits may maintain polymorphism of both mimetic and non-mimetic color traits through genetic linkage, despite weaker selection on non-mimetic traits. Such findings present a previously-unstudied way in which phenotypic diversity can be maintained in mimicry complexes and have further implications for color pattern diversity across the tree of life. |