Sexual dimorphism in the Chinese endemic speciesPachyhynobius shangchengensisFei, Qu and Wu, 1983 (Urodela: Hynobiidae)

Sexual dimorphism (SD) is a widespread phenomenon in most vertebrate species and is exhibited in a myriad of ways. In amphibians, sexual size dimorphism, in which females are larger than males, is the most common type, and sexual shape dimorphism varies among species. Different selection forces (sexual selection, fecundity selection, and ecological selection) that act differently upon the sexes form the consequence of SD. Thus, studies of SD provide information about the general intersexual divergence of the same species and allow insights into the impact of selective forces on the sexes. In this study, we analyzed morphometric data of the Shangcheng stout salamander,Pachyhynobius shangchengensis, an endemic and poorly known Chinese salamander, to examine sexual dimorphism in size and shape. The morphometric data included 15 characteristics of 68 females and 55 males which were analyzed using univariate and multivariate methods. A significant difference was found between the sexes in terms of both body size (snout-vent length) and some body shapes (e.g., head length and width, tail length and width, distance between limbs, and limb length and width) in this salamander. The longer snout-vent length in males may be attributed to sexual selection, longer and wider head in males may contribute to male-male competition, longer and wider tail in males may be attributed to energy storage and reproductive success, the larger distance between limbs in females is likely due to a fecundity advantage, and longer and more robust limbs in males may be related to reproductive or competitive behaviors. These results demonstrated that sexual dimorphism of different morphological traits is the consequence of different selection forces that act differently upon the sexes.

Invalidity of Hynobius yunanicus and molecular phylogeny of Hynobius salamander from continental China (Urodela, Hynobiidae)

Based on morphological and molecular analyses, Xiong et al. (2007) synonymized Hynobius yunanicus Chen et al. with Pachyhynobius shangchengensis Fei et al., both from continental China. Their study, however, was not substantial enough in that morphology of types of neither species was compared, only a partial mitochondrial cytochrome b (cyt b) sequence was employed, and data for H. chinensis was lacking. In order to reassess their conclusion, we morphologically examined type specimens of both species, and compared their complete cyt b (1141 bp) sequences, together with all the six recognized continental Hynobius species and some congeners from Japan and South Korea.