密点麻蜥的两性异形和雌性繁殖

蜥蜴繁殖成功率与其形态特征有密切的关系。作者在内蒙古乌拉特后旗采集密点麻蜥(Eremias multio-cellata) ,定量研究该种形态特征的两性异形和雌体繁殖特征,检验与成体形态特征相关的两性繁殖成功率差异是否能促进两性异形的进化。密点麻蜥成体个体大小无显著的两性差异,但头部大小两性差异显著;雄性个体的头长和头宽均大于体长相同的雌性成体。繁殖雌体于五、六月份排卵;在实验室条件下,雌体在六月下旬至七月下旬之间产仔。该种雌体年产单窝仔,每窝2 -4仔。窝仔重与雌体体长呈正相关,但雌体体长仅能解释很少一部分(约19 %)窝仔重的变异。窝仔数和幼仔重均与雌体体长无关。幼仔重与相对生育力(相对于雌体体长的窝仔数)呈显著的负相关,表明该种蜥蜴存在后代数量-大小之间的权衡。密点麻蜥雄体和雌体向较大体型方向进化的选择压力均相对较弱,与成体头部大小相关的两性繁殖成功率的差异是导致该种蜥蜴头部大小两性异形进化的主要原因动物学报52 (2) : 250 -255 , 2006]。

Sexual dimorphism and female reproduction in the multi-ocellated racerunner Eremias multiocellata ( Lacertidae )

Reproductive success and morphological traits are intimately linked in lizards. We collected adult multi-ocellated racerunners Eremias multiocellata from a population in Inner Mongolia (northern China) to quantify sexual dimorphism and female reproductive characteristics of this poorly studied viviparous, lacertid lizard, testing for the prediction that the evolution of sexual dimorphism is promoted by between-sex differences in reproductive success relating to adult morphological traits. Adults are sexually dimorphic in head size but not in body size, with males having longer and wider heads than do females of the same body length. Females ovulate from May to June and, under laboratory conditions, they give birth to young from late June to late July. Litter size ranges from two to four young. Litter mass is positively correlated with female SVL, but female SVL only explains a small portion (approximately 19%) of variation in litter mass. Both litter size and neonate mass are not correlated with female SVL. Neonate mass is negatively correlated with relative fecundity (litter size relative to female SVL), suggesting a trade-off between size and number of offspring in E.multiocellata. Overall, selective pressures towards large male and large females are both relatively weak in E.multiocellata, and the evolution of sexual dimorphism in head size results mainly from between-sex differences in reproductive success relating to adult head size.