Sometimes, males and females of the same species differ in traits linked with their ability to survive and reproduce. These differences, called sexual dimorphisms or polymorphisms are quite common in lizards, including anoles! Female brown anoles have a polymorphic back pattern while males are usually of a single pattern. A lot of work has tried to uncover why this back pattern polymorphism exists in nature and what advantages it offers these lizards. Rachana Bhave, a Ph.D. student with Robert Cox at the University of Virginia were interested in determining just how these male and female-like morphs of brown anoles differ in their morphology, behavior, and which traits influence survival.
Using a captive island population in Florida, Bhave et al. captured all of the lizards on the island and measured differences in morphology between the morphs, finding that female-like morphs tend to have higher survival as juveniles but not as adults. These morphs differed in their growth rates but did not experience different selective pressures, indicating perhaps a very complex control regulating the back pattern maintenance in this population. They also found that while female-like morphs tend to display at a higher rate, there weren’t any differences in the morphs probability to attack. They plan to integrate more physiological data such as growth or performance metrics to try and uncover the governing factors responsible for maintaining this back-pattern polymorphism. Awesome stuff to come!