One recent area of interest in the lab is the evolution of phenotypes. We are using macroevolutionary analyses to identify the ecological factors underlying the evolution of phenotypes. Then, using the tools of genomics and population genetics, we characterize the genomic architecture of the traits and we determine the evolutionary forces that have acted at the population level. This approach was used in our study of color polymorphisms in frogs. We analyzed two common color polymorphisms: the presence of a dorsal band and the green/brown polymorphisms. We discovered that the dorsal stripe in frogs evolved hundreds of time and is favored in terrestrial habitats. We demonstrated that variation at the ASIP genes was responsible for the stripe polymorphism in Ethiopian grass frogs (genus Ptychadena) and that the stripe phenotype evolved rapidly and recurrently in terrestrial frogs (Goutte et al. 2022). In contrast, we found that the green/brown polymorphism can persist for extended periods of evolutionary time in frogs and that polymorphic lineages switch habitats more frequently and have a greater rate of diversification than other groups. We then identified the locus responsible for the green/brown polymorphism in a group of African grass frogs, and demonstrated that this genomic region is evolving under long-term balancing selection, resulting in trans-specific polymorphism. These results provide a micro-evolutionary mechanism for the long-term persistence of color polymorphism observed at a macro-evolutionary scale (Goutte and Boissinot, submitted).
Another phenotypes we have been interested in is the presence of cephalic appendages in snakes, in particular vipers. Using a macroevolutionary analysis we demonstrated that ocular horns are associated with desert habitats while nasal horns are associated with forest habitats. This analysis indicates that horns evolve convergently in vipers (Busschau and Boissinot, 2022). We are in the process of determining the genes that are underlying the horned phenotype in desert vipers (genus Cerastes and Bitis) and to assess the role of selection in the evolution of this phenotype.