昭觉林蛙的食性与两性异形

Diet and sexual dimorphism of Rana chaochiaoensis

对采自1998年5月至2003年10月的昭觉林蛙Rana chaochiaoensis解剖428只(♀202,♂184,亚成体42只)分析食性,测量体长大于40 mm的成体151只(♀81,♂70)作两性异形研究。解剖结果表明,昭觉林蛙以动物性食物为主,两性的食性无显著性差异,食性不是影响两性异形分化的原因。t检验结果表明,昭觉林蛙成年雌雄个体在前臂宽/前臂长存在极显著差异。协方差分析结果显示,昭觉林蛙雌雄个体头宽、吻长、鼓膜直径、眼径、前臂长、前臂宽、手长、后肢全长、胫长和足长存在显著差异。两性异形主要系性选择压力的结果。昭觉林蛙属于成年雌雄个体大小无显著差异的类型。雄性昭觉林蛙的前臂明显比雌性的粗壮,第一指基部具有发达的婚垫,表面具细密角质刺,以加大拥抱摩擦,增强拥抱能力,避免雌蛙逃脱。雄性昭觉林蛙没有声囊,但后肢较长和具有较雌性发达的蹼,有利于提高自身追逐雌性的能力,以提高繁殖成功机率;而雌蛙发达的后肢则有利于提高跳跃能力,快速躲避干扰和威胁。

The 428 specimens of Rana chaochiaoensis collected from May 1998 to October 2003 were anatomized （♀202, ♂184, subaduhs 42） for diet analysis; 151 adult frogs whose body lengths were larger than 40 mm were measured （♂81, ♀70） for sexual dimorphism study. The diet analysis showed that R. chaochiaoensis gave priority to animality food and there was no significant discrepancy in cliet between male and female frogs. The food habits didn＇t lead to their sexual dimorphism polarization. The results of t-test indicated that there was significant discrepancy in width and length of forearm between male and female adult R. chaochiaoensis. The results of univariate analysis of variance showed that there was significant discrepancy in head width, snout length, tympanum diameter, eye diameter, forearm length, forearm width, hand length, length of hindlimb, tibia length and foot length between male and female adult frogs. Sexual dimorphism was primarily determined by the ultimate sexual selection. There was no significant difference in body size between male and female R. chaochiaoensis. Forearm in adult male R. chaochiaoensis was stronger than female＇s. The first finger base in adult male frog had nuptial pad with fine and dense cutin tubercles, which could increase embrace friction, strengthen embrace ability and avoid female frog escaping. Male R. chaochiaoensis had no vocal sac. However, its longer hindlimb and more developed web than female＇s were helpful to improve its capacity of chasing female, which could successfully increase mating rate. Developed hindlimb of female could enhance its ability to jump, which was useful for female keeping away rapidly from disturbance and threat.