母代雌蜂数、进果时间及非传粉小蜂对传粉榕小蜂后代数量及性比的影响

【目的】对性比的研究有助于我们理解自然界生物的选择压力及其所产生的原因和结果，榕树和榕小蜂之间的互惠共生关系以及生物学和生态学特性使其成为研究性比和局域配偶竞争模型（local mate competition）的理想材料。本研究旨在探明榕小蜂性比调节和进化机制。【方法】对分布于西双版纳地区的鸡嗉子榕Ficus semicordata进行了人工控制性放蜂实验。测定了母代雌蜂数量及其进果时间间隔、非传粉小蜂Sycoscapter trifemmensis数量对传粉榕小蜂Ceratosolen gravelyi后代数量（成蜂数量）和性比的影响，并分析了小蜂后代数量和性比的相关性。【结果】在榕果发育期一致的前提下，随着母代雌蜂数量的增加，每头雌蜂的平均后代数量明显下降(P<0.001)，后代性比显著升高(P<0.001)，后代数量和性比呈显著负相关(P<0.05)；随着雌蜂进果间隔的延长，后代数量亦呈现下降趋势，且性比增大，放2头雌蜂和3头雌蜂的处理呈同样趋势，但差异均不显著(P=0.87; P=0.49)，小蜂后代数量与性比无显著相关性(P=0.86)。此外，非传粉小蜂数量与传粉小蜂后代数量呈显著负相关(P<0.001)，与传粉小蜂性比呈正相关(P<0.001)，小蜂后代数量和性比同样呈现显著负相关(P<0.001)。【结论】本实验模拟了自然界中榕 蜂的相互作用，所得结果有助于我们理解自然状态下榕小蜂性比调节模式和机制，以及榕 蜂互利共生系统的进化机制。

Effects of foundress number,foundresses entry interval and non-pollinating wasps on clutch size and offspring sex ratio of pollinating fig wasps (Hymenoptera: Agaonidae)

【Aim】The study of sex ratio variation is important for understanding the causes and consequences of selective pressures. The pollinating fig wasps are widely used in researches on sex ratio and local mate competition (LMC) because of theoretical assumptions of their biological and ecological feature resemblance. Our study aimed to explore the mechanism of sex ratio adjustment and evolution in fig wasps. 【Methods】 We conducted controlled introduction experiments on Ficus semicordata in Xishuangbanna, and the first receptive day was defined firstly for each experimental fig by observing the behavior of the pollinator (Ceratosolen gravelyi). Then we tested the effects of foundress number, time interval of foundress entry and density of non pollinating fig wasps (Sycoscapter trifemmensis) on clutch size (the number of adult wasps) and the offspring sex ratio of pollinating fig wasps, as well as the relationship between clutch size and the offspring sex ratio in each treatment. 【Results】 When foundress number increased, the mean clutch size per foundress significantly decreased (P<0.001) and the offspring sex ratio increased significantly (P<0.001), and the offspring sex ratio was negatively related to the clutch size per foundress for individual figs (P<0.05). As the foundress entry interval prolonged, the clutch size per foundress decreased and the offspring sex ratio (P=0.86) was less female-biased, and the similar trends were found between 2 foundresses (P=0.87) and 3 foundresses treatments (P=0.49). The density of non-pollinating fig wasps significantly reduced clutch size (P<0.001) and increased the offspring sex ratio of pollinating fig wasps (P<0.001), and a significantly negative relationship was found for individual figs between clutch size and the offspring sex ratio (P<0.001). 【Conclusion】 This study simulated the natural condition of interaction between figs and fig wasps, so the results can help us understanding the pattern and mechanism of sex ratio allocation in natural condition, and the evolution mechanisms of mutualistic symbiosis between figs and fig wasps as well.