Molecular Evolution of Visual Opsin Genes during the Behavioral Shifts between Different Photic Environments in Geckos

摘要

Reptiles are the most morphologically and physiologically diverse tetrapods,with the squamates having the most diverse habitats.Lizard is an important model system for understanding the role of visual ecology,phylogeny and behavior on the structure of visual systems.In this study,we compared three opsin genes(RH2,LWS and SWS1)among 49 reptile species to detect positively selected genes as well as amino acid sites.Our results indicated that visual opsin genes have undergone divergent selection pressures in all lizards and RH2 and LWS suffered stronger positive selection than SWS1.Twelve positively selected sites were picked out for RH2 and LWS.Moreover,many diagnostic sites were found between geckos and non-gecko lizards,most of which were located near the positively selected sites and some of them have already been reported to be responsible for significant shifts of the wavelength of maximum absorption(λ_(max)).The results indicated that the gecko lineage accelerated the evolution of these genes to adapt to the dim-light environment or nocturnality as well as the switch between nocturnality and diurnality.