Sexual dimorphism of plateau brown frog in Haibei region of Qinghai in China

Abstract

Rana kukunoris (plateau brown frog) is an amphibian species endemic to the Qinghai-Tibet Plateau. In this study, 60 adult specimens (30 ♀, 30 ♂) were collected from the Haibei Alpine Meadow Ecosystem Positioning Station of the Chinese Academy of Science and measured for 25 morphological traits, including adult body weight and body length. The morphological indexes of male and female individuals were compared and analysed. The results showed that 11 morphological traits in females, including body length and interorbital spacing, were significantly higher in value than those in males. The mean SVL of famales (50.10 ± 1.04) was larger than of males (48.43 ± 1.38), the sexual index was 0.033. The mean weight of females (10.93 ± 0.67) was 1.168 times that of males (9.36 ± 0.70). Among all traits, 23 morphological characteristics in females and 22 in males showed allometric effects. Covariance analysis of morphological features with snout–vent length as the covariate demonstrated significant correlations between body weight, internal distance, interorbital distance, forearm width, interior metatarsal, mouth-to-spat distance, third finger length, and first finger length, indicating that, when considering snout–vent length, significant differences were observed. Our results showed that females were larger than males in terms of sexual dimorphism. Such sexual dimorphism may be a result of the combined effects of fecundity selection theory and environmental factors. The measured values also provide a reference to explore sexual dimorphic traits between sexes and their adaptation to the cold environments.