Variation in sexual dimorphism between two populations of the Pyrenean salamander Euproctus asper from ecologically different mountain sites

Morphological variation and ecological characteristics of habitats of two populations of the Pyrenean salamander Euproctus asper from the Flumen river, Prepyrenees, and the Salto del Pis torrent, Central Pyrenees, were studied to determine whether intraspecific differences in body form and sexual dimorphism occur and if they can be functionally related to ecological differences between the two study sites. While the Flumen river was found to be characterized by a Mediterrenean-influenced moderate mountain climate and high eutrophication. the Salto del Pis torrent represents a typical alpine habitat with long winters accompanied by snow cover, frequent avalanches, and short, mostly cool summers. Uni- and multivariate comparisons were performed on 12 size-adjusted measures of body form and weight from a total of 85 living specimens, grouped according to sex and geographic origin, Major differences were found mainly in those characters that manifest sexual dimorphism,hism. such as head size, tail length, tail depth, leg length, and body weight. Sexual dimorphism was more strongly expressed in the Central Pyrenean population where females showed longer tails and smaller heads, while males had mole robust rails and higher body weights compared with the Flumen population. Based on ecomorphological considerations and previous genetic studies, we argue that geographic divergence in sexual dimorphism of the Pyrenean salamander reflects longterm evolutionary adaptations in response to increased selection pressures favouring high reproductive efficiency and reduced intersexual competition under alpine, high-mountain climate conditions.