• sexual dimorphism
• ecological plasticity
• lizards
• islands

Sexual dimorphism is the natural phenomenon that results in the presence of significant differences between males and females of the same species. Due to isolation and their extremely diverse characteristics, islands are the perfect areas to study natural phenomena. In this study we analyse the differences in the sexual size dimorphism of two lacertid species, Podarcis siculus and P. muralis, among the different islands of the Tuscan Archipelago and among them and the mainland, considering also the role of island biogeography and ecological plasticity of the two species. P. siculus and P. muralis are known to have an extremely dynamic and fast evolution, thus they have been chosen as model species to explore the effect of islands isolation on the ecology and, in particular, on sexual dimorphism. Sampling session occurred from during the reproductive season of the two species, from May to July of two consecutive years. We captured individuals from all the seven island of the Tuscan Archipelago as well as individuals from other mainland localities, to be used as comparison. The standard measurements taken from the lizards have been used to establish if there were any differences in the sexual dimorphism among the lizard populations of the Tuscan Archipelago islands, and among them and the continent population. We found significant differences in the degree of sexual size dimorphism between the two species, among the different islands populations and among them and the mainland. Moreover, we found significant differences among the P. muralis populations within the same island as well. We assumed that sexual size dimorphism regulate itself for the best according to island ecological characteristics. Further morphometric and ecological investigations are required to shed more light on the mechanisms of sexual size dimorphism.