The Herpetological Journal

pp.465-473

Authors: Antonia M. Cirer And Juan-pablo Martinez-rica

Abstract: The variation in morphological and colouring features shown by the insular lacertid populations of Podarcis pityusensis is discussed from the point of view of their adaptive advantages to specific insular ecosystems. Insularity factors, i.e. area and island-age, have been found to be related t.o average body size, and the average luminosity of each population. Populations tend to show a size increase, a greater morphological homogeneity and darker dorsal colouring on smaller and older islands. The advantages of larger size and melanism are discussed as well as their possible causes in the insular microecosystems of the Pityusic Archipelago. Genetic drift seems to play a secondary role, whereas a positive selection in favour of melanism and giant ism is observed. Both features are not linked as cause and effect, but seem to share a common cause: isolation and time enough to allow selection to take place. Predation, though slight in degree, does exist, and seems to be one of the selective pressures favouring melanism, together with the parallel trend towards an increase in body size and the need to an effective thermoregulation during the early hours of the day.