对叶榕传粉小蜂性比率的调节和稳定

传粉榕小蜂呈现偏雌的性比率,单双倍体性别决定系统、局域配偶竞争和近交效应被认为是调节偏雌性比率的3个主要机制。通过研究影响对叶榕传粉小蜂性比率的因素,结果表明传粉榕小蜂的偏雌性比率随局域配偶竞争强度的降低而增加;受母代雌蜂交配次数的影响,随着母代雌蜂交配次数的增加,子代的偏雌性比率逐渐降低,这一结果首次揭示了传粉榕小蜂的交配制次数对性比率的影响,并在个体水平上定量了性比率变异与雌蜂交配频次的关系。传粉小蜂的性比率与共生的非传粉小蜂的关系,非传粉小蜂的介入直接减少了传粉小蜂的数量,甚至对传粉小蜂的种群有显著影响,结果发现非传粉小蜂对传粉小蜂雌雄性的分配比率没有显著影响,传粉榕小蜂仍能正常地进行繁殖。传粉与非传粉者小蜂之间作用关系的确定,可为进一步理解两者的稳定共生的机制提供科学证据。

Adjustment and stabilization of sex ratio in Ceratosolen solmsi marchali

All fig-pollinating wasps share a similar life cycle. Generally some number of mated foundress wasps enter a receptive male fig, lay eggs in ovaries of flowers, then and die. The offspring finish development within the ovary. The wingless adult males first emerge from natal galls, and crawl around the interior of syconium, and mate with females still contained in galls. The mated female wasps then emerge from their galls, gather pollen, leave the syconium, and disperse to begin the cycle anew. The natural history of fig-pollinating wasps makes them well suited for the study of sex ratio evolution, especially local mate competition (LMC), and good fits have been obtained between empirical data and model preditions incorporating LMC and inbreeding effects at the population level. At present, LMC, inbreeding and haplodiploidy are generally regarded as three mechanisms of adjusting progeny sex ratio in fig wasps. Undoubtedly, the haplodiploid genetic system favors a female-biased sex ratio, and its effect is independent of any influence of LMC or inbreeding, a mother may adjust the sex ratio of her brood by fertilizing or not fertilizing eggs with sperm she stores in the spermatheca. However, LMC and inbreeding cannot explain all variation observed in sex ratios. In this study, we analyzed the impact on pollinator sex ratio of pollinator adjustment and non-pollinators. The results showed: (i) Sex ratio increases with reduced LMC intensities; (ii) The proportion of males drops with increasing foundress mating times, this being the first reported negative relationship between sex ratio and mating times; (iii) non-pollinating fig wasps did not affect the sex ratio of fig-pollinating wasps. Philotrypesis drained food resources from pollinators and starved them to death. Apocrypta bakeri parasitized pollinators or Philotrypesis and directly killed them. Though three species of non-pollinating fig wasps decreased pollinator numbers, no significant impact on pollinator sex ratio was found. Ensuring normal reproduction of fig-pollinating wasps might be a key factor that enables non-pollinating fig wasps to successfully invade the fig-pollinator mutualism system and coexist in the long term.