Variation in size and shape: sexual dimorphism in the southern banded newt, Ommatotriton vittatus (Caudata: Salamandridae)

Abstract

One of the main factors creating intraspecific morphological variation, sexual dimorphism (SD) could be expressed as adult male and female animals having different body sizes or shapes. Female-biased sexual dimorphism has been documented in the vast majority of amphibians and more than half of salamanders. In this study, 18 morphometric characters were used to analyze the size and shape dimorphism of the southern banded newt, Ommatotriton vittatus, a species whose congeners exhibit male-biased dimorphism. In this way, the hypothesis that species within the same genus would have similar sexual dimorphism (for example, male- or female-biased) was tested. Results of the current study confirmed the existence of male-biased sexual size and shape dimorphism in O. vittatus. For instance, snout-vent length and tail length were found to be significantly different between sexes, with males being larger. Moreover, males have larger forelimbs and hindlimbs than females. Data from the present study also indicated significant male-biased differences in five (head length and width, eye diameter, distance between the orbit and naris, and internarial distance) out of eight head characters. This result supports the assumption that species within the same genus will have a similar tendency for sexual dimorphism.