Variation in skull size and shape in a newt species with male-biased sexual dimorphism

Abstract

According to Rensch’s rule, sexual size dimorphism (SSD) increases with body size in groups where males are the larger sex and decreases when females are larger. The genus Ommatotriton represents a well-defined lineage with male-biased SSD within a group of Eurasian newts otherwise characterised by females being larger than males. In the present paper, we explore sexual dimorphism in skull size and shape for populations of the banded newt Ommatotriton ophryticus, applying geometric morphometrics to investigate size-dependent allometric shape variation. Sexual dimorphism in skull size was not correlated with the size of males, rejecting Rensch’s rule. Sexual dimorphism in skull shape of O. ophryticus is entirely due to allometric, size-related shape changes between sexes.