Sexual size and shape evolution in European newts (Amphibia: Caudata: Salamandridae) on the Balkan Peninsula

Abstract

We used a phylogenetic perspective in an examination of the direction and extent of sexual dimorphism in body size and body shape in European newts from the Balkan Peninsula (alpine newts, Mesotriton alpestris; crested newts, Triturus cristatus superspecies; smooth newts, Lissotriton vulgaris). We found a strong, female-biased sexual size dimorphism (SSD) in the analysed clades of alpine newt, whereas within crested newts we found a less stringent female-biased SSD in Triturus carnifex, Triturus macedonicus and Triturus karelinii, and no significant SSD in T. cristatus or Triturus dobrogicus. Among the smooth newts, we found male-biased SSD in Lissotriton vulgaris vularis and Lissotriton vulgaris greacus and no SSD in Lissotriton vulgaris meridionalis. Most of these newts also exhibit a significant sexual dimorphism in body shape, which varied more randomly than body size, regardless of SSD level. Female and male body size as well as the degree of SSD displayed statistically significant phylogenetic signal, while sexual dimorphism in body shape was phylogenetically independent. The relationship between independent contrast data for female size and male size indicated that SSD in European newts could be driven by a disproportionate increase in female size as increase in female size was not accompanied by a proportional increase in male size.