Sexual dimorphism describes existence of phenotypic differences between males and females, and also involves a series of different traits such as coloration, size, shape and behavior within species. In the present study, we investigated sexual dimorphism in two dimensions of shape and body size in the tree frog, Hyla savignyi (Audouin, 1827) using 13 males and five females from Lorestan Province in western Iran. Three patterns have been proposed for sexual dimorphism in amphibians, according to body size (SSD): Female-biased (females larger than males), male-biased (males larger than females), and unbiased (males equal to females). Sexual size dimorphism (SSD) was computed according to the sexual dimorphism index (SDI), where SDI= (average length of larger sex/average length of smaller sex) and statistical significance for a hypothesis of SSD of the frogs were tested using independent t-test. As well, ANOVA was conducted to compare vectors of means of the two sexes. Although the SDI was 0.07 indicating an intersexual difference in body length (female-biased SSD), SVL did not differ significantly among females and males according to the t-test; P≥ 0.05. In the present study, the ANOVA analysis distinguished a significant difference (P≤ 0.05) in four traits (ND: Distance between nostrils; IMTL: Inner metatarsal tubercle length; WMT: Width of metatarsal tubercle and WUE: Width of upper eye lid). So, in this species, snout–vent length (SVL) is not significantly different betwaleen adult males and females, but there are significant shape differences between sexes.
