Schematic illustrating how testosterone facilitates sex-specific gene expression. Testosterone (T), which circulates at higher levels in males (right) than in females (left), binds to the androgen receptor (AR), which translocates to the nucleus, recruits sex- and region-specific cofactors, and binds to an androgen response element (ARE), leading to altered transcription of an ARE-proximal color gene.
COLOR EVOLUTION I am interested in mechanisms underlying why and how lizards have colorful traits. Currently, I am studying how the evolution of gene expression among Sceloporus species contributes to shifts from sexual dimorphism to sexual monomorphism, which has occurred in multiple independent lineages.
Sceloporus lizards can evolve sexual monomorphism two ways. First, males can lose ancestral ventral coloration, resulting in males and females with white abdomens. Second, females can gain ventral coloration, resulting in males and females with colorful abdomens. The mechanisms underlying these shifts are so far unknown and represent a fruitful area of research that I am excited to explore. However, we know that testosterone is necessary for inducing coloration in many species, so the interaction of testosterone with the genome, through its activated androgen receptor, the recruitment of co-factors, or the gain or loss of functional androgen response elements represent avenues by which evolution can act.
Further, in collaboration with Dave Parichy and his lab, I am characterizing cell populations within Sceloporus skin that develop in response to testosterone.
Reaction norms of sprint speed, abdominal hue, and throat hue in male prairie lizards.
COLOR AS A SIGNAL Using the prairie lizard, which has thermally sensitive ventral coloration, we showed that individual sensitivity to thermal conditions covaried between ventral coloration and sprint speed at the individual level. Further, we showed that individuals who were "bluer" at one temperature were "bluer" at all temperatures. Together, these results suggested to us that the bluest individuals are the fastest, which may have important consequences for fitness. Read about this work here!