鸡嗉子榕隐头果雌花期特征对传粉榕小蜂选择的影响

Effects of Ficus semicordata Characteristics at Female Phase on the Choice of Pollinating Fig Wasp

摘要:

为了探讨榕树隐头果的发育期、性别、大小等外部特征对传粉榕小蜂选择的影响，采取人为控制雌花期的方法，对鸡嗉子榕（Ficus sermicordata）及其传粉榕小蜂（Ceratosolen gravelyi）的选择行为进行研究。结果表明，在隐头花序发育到雌花期后，如果阻止传粉小蜂进入，隐头果会继续生长。直径较小的雌果和雄果的进蜂量较多，且在雌雄果同时存在时，小蜂仍然会选择进入雌果，但进蜂量显著低于雄果。小蜂优先选择进入雌花期前期的隐头花序，雌雄果皆有此特点。对于相同发育期的隐头果，果径和进蜂量呈正相关关系，说明对于相同发育期的隐头果，小蜂更倾向于进入较大的隐头果。因此，真正控制小蜂行为的是隐头花序所处的发育期，以及不同发育期所产生的化学挥发物，而非隐头果直径大小。这为进一步研究榕-蜂系统的稳定机制提供依据。

Abstract:

The interaction between pollinating fig wasps (Agaonidae) and their host fig trees (Ficus) is a striking example of an obligate pollination mutualism. Successful pollination of fig trees depends on a specific species of fig wasp managing to find figs of the correct host plant, at their correct stage of development. Encounters between receptive figs and their pollinators are attained by figs emitting species-specific volatile chemicals to attract their fig wasps. However, whether and how the choice of fig wasps can be influenced by the characteristics of receptive figs are still controversial. The female phase of Fiucs sermicordata was deemed by whether fig wasps were willing to enter figs, the different developmental phase of male and female figs in receptivity were acquired at the same time by preventing figs from being pollinated by fig wasps, and the diameter of figs was also measured to examined how fig wasps preferences can be reflected by the size, developmental phase and gender of figs. The results showed that figs would keep growing if they were prevented from being pollinated during female phase, smaller figs were more likely to be entered by more fig wasps for both male and female figs, and fig wasps preferred younger figs. Some of fig wasps still chose female figs to enter when both receptive male and female figs were accessible at the same time, although the wasps number was significantly smaller than those of entering male figs. Although the correlation between fig diameter and foundress number was positive within figs in the same developmental phase, such correlation only significant among four treatments of male figs. The results were not consistent with Ficus pertusa and Ficus hispida. These implied that different Ficus species might have different mechanism to control their pollinator's choice during female phase, it is developmental phase in receptivity and the change of chemical volatile as consequence rather than fig diameter has the direct effect on the choice of fig wasps, and fig wasps depend on olfactory rather than visual cue to locate their host figs. The results could help for further understand the stabe mechanisms of fig-fig wasps.