浙江丽水虎纹蛙形态特征的两性异形和食性

Sexual Dimorphism in Morphological Traits and Food Habits in Tiger Frogs, Hoplobatrachus rugulosus in Lishui, Zhejiang

用数显游标卡尺测量了407只2001-2003年9月下旬至10月上旬浙江丽水罚没的死亡虎纹蛙的体长等10个形态指标,结果表明:雌性成体体长(SUL)大于雄性成体,幼体形态无显著两性差异;ANCOVA去除SUL差异的影响后,雌性成体的头长和后肢长大于雄性成体,前肢长、眼径和耳径则小于雄性成体.前肢两侧对称性的偏移度成体大于幼体,雌性大于雄性;后肢两侧对称性成幼体和两性无显著差异.10个形态指标主成分分析的前三个主成分共解释64.6 %的变异:第一主成分中头宽、眼径和耳径,第二主成分中后肢长,第三主成分中眼间距和鼻间距分别有较高的正负载系数.用Nikon SMZ-1000解剖镜鉴别277只个体胃内容物中的食物种类,发现其秋季食物以节肢动物为主;成幼体和两性食物生态位宽度为3.42～5.25,食物生态位重叠度较高为0.93～0.98.分析表明,虎纹蛙局部形态特征的两性差异微弱,而体长两性异形差异显著;雌体具有较大的体形与食性无关,而可能与生育力选择的作用有关.

We used tiger frogs (Hoplobatrachus rugulosus) collected from Lishui (Zhejiang, eastern China) to study sexual dimorphism in morphological traits and food habits. Females larger than 80 mm SUL (snout-urostyle length) and males larger than 70 mm SUL were considered to be adults, and others to be juveniles. The frog is sexually dimorphic, with females being the larger sex. Juveniles were not sexually dimorphic in any of the examined morphological traits. Head length and hind-limb length were larger in adult females than in adult males and fore-limb length, eye diameter and tympanum diameter were larger in adult males than in adult females, when influence of variation in body size (SUL) was removed using ANCOVAs. Other examined morphological traits did not differ between adult females and adult males. The magnitude of hind-limb length deviating from the bilateral symmetry did not differ between adults and juveniles and between both sexes, whereas the magnitudes of fore-limb length deviating from the bilateral symmetry were greater in adults than in juveniles and were greater in females than in males. A principal component analysis resolved three components (with eigenvalues  1) from ten size (SUL)-free morphological variables, accounting for 64.6% of variation in the original data. The first component (26.9% variance explained) had high positive loading for size-free values of head width, eye diameter and tympanum diameter, the second component (19.7%) for size-free value of hind-limb length, and the third component (18.0%) for size-free values of interocular length and internasal length. Adult females had lower scores on the first axis of a principal component analysis than did adult males, but the score on the second and the third axes did not differ significantly between adult females and adult males. The tiger frog is an insectivorous species, but it also feeds on invertebrates other than insects. Frogs of different ages and sexes, in various degrees, differed in food niche width and breadth. However, no direct evidence shows a noticeable contribution of the divergence in head size to the segregation of food niche between males and females, which is considered to important to mitigate the competition for food between both sexes.