Sexual size difference in Triturus newts: geographical variation in Yugoslav populations

Abstract

Our study on the variation of sexual size difference (SSD) in eight morphometric characters expressing over-all size relations, feeding and locomotion abilities was carried out on a considerable number of population samples of T. vulgaris, the T. cristatus complex and T. alpestris. Females of T. alpestris were considerably larger than males, and to lesser extent in the T. cristatus complex, while in T. vulgaris the sexes were about the same size or the males were somewhat the larger sex. The effect of sexe differences was more pronounced than population sample effect for most characters. Our analysis of SSD patterns suggests that intersexual difference is a variable condition that is not constrained in its distribution by geographic proximity of analyzed populations, population altitudes and species body size. In the T. alpestris populations with facultative paedomorphosis, metamorphic females and males showed much greater size differentiation than paedomorphic ones. We discuss the potential influence of different selective pressures on the extent of SSD in newt species.