蜡皮蜥的两性异形和繁殖输出

为研究蜡皮蜥(Leiolepis reevesii)两性异形和繁殖输出，于2002、2003年4月下旬从海南乐东一种群捕获423头蜡皮蜥。经检测得到繁殖雌体的最小体长为89．0mm，据此判定≥89．0mm的个体为性成熟。研究结果表明：①蜡皮蜥具有两性异形，雄性大于雌性且具有较大的头部。成体雄性头长和头宽随体长的增长速率大于雌性，幼体头长和头宽随体长的增长速率无显著的两性差异。以性别和年龄(成、幼体)为因子的双因子ANOVA比较两性头长和头宽与体长的回归剩余值发现，雄性头部大于雌性，幼体头部相对大于成体。②饲养于实验室的母体中有42头于2002、2003年5月22日～7月16日产出正常卵，这些繁殖雌体具有年产多窝卵的潜力。窝卵数和卵重的变异系数分别为0．18和0．13，前者变异度大于后者。窝卵数、窝卵重和卵重均与母体体长无关。卵重与相对生育力之间无显著的负相关性，表明蜡皮蜥缺乏卵数量与卵大小之间的权衡。相对窝卵重与母体体长呈显著的负相关，表明较小的母体具有相对较大的繁殖输出。因雌体繁殖会滞缓其生长，小母体具有相对较大的繁殖输出，至少部分地解释了雌性蜡皮蜥的成体为什么个体较小。

Sexual Dimorphism and Reproductive Output in Reevese's Butterfly Lizards,Leiolepis reevesi

In late April of 2002 and 2003,we collected 423 Reevese's butterfly lizards (Leiolepis reevesii) from a population in Ledong,Hainan,to study sexual dimorphism and reproductive output.The minimal reproductive female in our sample was 89.0 mm snout-vent length (SVL).Individuals larger than this size were arbitrarily judged as adults.The lizard is sexually dimorphic,with males being larger in both body size and head size.The rate (slope) at which head size (both head length and head width) increased with increasing SVL was greater in male adults than in female adults,whereas it did not differ between male and female juveniles.A two-way ANOVA,with sex and age (adult and juvenile) as the factors,on the residuals of the regressions of head length and head width on SVL showed that heads were larger in males than in females,and that juveniles had larger heads relative to SVL than did adults.Females maintained in the laboratory laid eggs between late May and mid-July,and they had the potential to lay multiple clutches per year.The coefficient of variation was 0.18 for clutch size and 0.13 for egg mass,indicating that clutch size was more variable than egg mass.The clutch size,clutch mass and egg mass were all independent of maternal size (SVL).The egg mass was not negatively correlated with relative fecundity,suggesting that the trade-off between size and number of eggs was absent in the lizard.The relative clutch mass was negatively correlated with maternal size,indicating that the smaller reproductive female had the relatively greater reproductive output.Given that a female's reproduction retards her growth,the relatively greater reproductive output in smaller females at least partly explains why females have the smaller adult size than do males.