Color variation and mate choice in a lacertid lizard

Coloration plays a crucial role in sexual selection. Stejneger's grass lizard (Takydromus stejnegeri) exhibits a diverse range of body colorations, including complex combinations of green or brown and striped or non-striped patterns in both sexes. In order to clarify the relationships among the variation of body coloration, body condition, and mate preference, we conducted a capture-mark-recapture survey in the wild and mate choice experiments in the laboratory. Analysis of data from 2,497 marked individuals revealed that adult females typically exhibit green patches on their sides, whereas adult males tend to display white stripes on their backs during the breeding season. These colorations did not correlate with their body condition. In the mate choice experiments, we found that green females preferred green males, while brown females preferred brown males. Conversely, males did not demonstrate a significant preference for both colors. Our findings suggest that the varied colorations of T. stejnegeri are influenced by life stage, sexual maturity, and potentially linked to assortative female choice. The maintenance of color variation is a fascinating subject in evolutionary biology, with sexual selection and mimicry often cited as two of the primary underlying mechanisms. However, long-term population monitoring and studies involving large sample sizes are rare, especially in reptiles—a group with elusive habits—where research is particularly scarce. This study has gathered an extensive collection of research samples to monitor seasonal variation in body color among individuals within the population and has conducted experiments on sexual selection to substantiate the maintenance of variation. We believe this research approach offers a compelling case study for investigating color variation.