Context-dependent expression of sexual dimorphism in island populations of the common wall lizard (Podarcis muralis)

The condition-dependent sexual dimorphism model explains the evolution and maintenance of sexual dimorphism in traits targeted by sexual selection, and predicts that the magnitude of sexual dimorphism depends on the variability of individual condition, male traits being more variable than female corresponding traits. Most convincing examples concern insects, while studies among vertebrates are scanty because manipulating condition often is not possible, and the time to reach sexual maturity may be too long. Islands offer a unique opportunity to compare how the environment affects the expression of sexual dimorphism, since they represent ‘natural experimental sets’ in which different populations of the same species may experience alternative environmental constraints. We investigated the occurrence of context-dependent expression in sexual dimorphism of head shape in insular populations of the common wall lizards (Podarcis muralis) inhabiting the Tuscan Archipelago (Tyrrhenian Sea). Alte...