Lizard species on three islands off the Mexican Pacific Coast: effects of insularity

This study provides a descriptive panorama of the lizard communities on 3 islands and the mainland on the Pacific coast of Mexico, estimating the effect of insularity (ecological changes between lizards on the islands and on the mainland) on lizard populations. The panorama included the number of species, encounter frequency and age classes. The insularity effects were estimated by comparing these variables, as well as basking behavior, activity related to microclimate, and perch height among the islands and the mainland. Of 11 species recorded, 8 occurred on the islands; however, every insular community was composed of 3 to 5 species (4 are protected by Mexican law). The encounter frequency for all species ranged between 11 and 0.1 individuals per hour. Lizard communities were predominantly composed of adults. Only 2 lizard species, Aspidoscelis communis and A. lineattissima, were shared among all sites, showing no insularity effects on the encounter frequency nor basking behavior. There were signs of insularity, however, on age classes and a clear effect on perch height, suggesting niche expansion. The study contributes to the regional knowledge of lizard species, as well as to ecological theories such as niche expansion and density compensation.