两种Eupristina属小蜂对宿主榕果挥发物和合成信息素的行为反应

高榕,雌雄同株,与其共生的形态高度相似的传粉小蜂Eupristina altissima与非传粉小蜂Eupristina sp.均为果内产卵。利用Y型嗅觉仪生物测定法研究E.altissima和Eupristina sp.对不同发育期高榕榕果挥发物以及合成信息素混合物的行为反应差异。结果表明:E.altissima和Eupristina sp.对高榕雌花期榕果挥发物具极显著趋向行为,对高榕雄花期榕果挥发物具极显著驱避行为,表明E.altissima与Eupristina sp.雌蜂能够敏锐辨别高榕雌花期和雄花期榕果的挥发物,快速远离雄花期榕果,并实现对宿主雌花期榕果的定位。但是,E.altissima与Eupristina sp.对其它发育时期榕果挥发物的行为反应具有差异性,前者对雌前期榕果和传粉或产卵后榕果释放的挥发物存在显著的趋避反应,而后者无明显的行为偏向性,表明E.altissima能够识别雌前期榕果和传粉或产卵后榕果,可避免误入其中而无法繁殖后代,Eupristina sp.则不具备这种识别能力。E.altissima和Eupristina sp.小蜂对合成信息素的行为反应也高度相似,表现为芳樟醇、苯乙烯,以及苯乙烯和金合欢醇的交互作用对两种小蜂选择行为影响显著,组合A_1B_2C_2(0.5%Linalool+1%Benzyl ethylene+1%Farnesol)的混合信息素对两种小蜂具有极显著的驱避作用,而组合A_2B_1C_1(1%Linalool+0.5%Benzyl ethylene+0.5%Farnesol),A_2B_1C_2(1%Linalool+0.5%Benzyl ethylene+1%Farnesol),A2B2C1(1%Linalool+1%Benzyl ethylene+0.5%Farnesol)的混合信息素对其具有极显著的吸引作用,但两种小蜂对组合A_1B_1C_1(0.5%Linalool+0.5%Benzyl ethylene+0.5%Farnesol)的行为反应存在差异。两种小蜂对榕果挥发物和合成信息素的反应异同,可能与其触角结构的差异密切相关。研究结果为探究榕-蜂共生体系的化学信号传导机制提供科学依据。

Responses of two Eupristina wasp species to fig volatiles of Ficus altissima and infochemicals

Fig trees are pollinated by fig wasps, which also oviposit in female flowers. They had formed obligate mutualism in their long co-evolution process. Ficus altissima (Ficus, Moraceae) is a monoecious fig plant, both the pollinating Eupristina altissima and non-pollinating Eupristina sp. symbiosis with Ficus altissima were oviposited within the syconia. Pollinating Eupristina altissima and non-pollinating Eupristina sp were highly similar in morphology, only with a slight difference on body color, antenna, fore leg coxal comb and pollen pocket for their female wasps, no morphological differences found so far between their male wasps. Fig wasps mainly located their hosts by recognizing the chemical signal released from the syconia. Also the encounter of the mating partners is fundamental for the stability of their interaction, In this study, we applied a Y-tube (binary choice) olfactometer to test the responses of E. altissima and Eupristina sp. to fig volatiles of different developmental phase of Ficus altissima and infochemical mixture. Results showed that:(1) both E. altissima and Eupristina sp. represented significant preference to the fig volatiles of female syconia, and repelled to the fig volatiles of male flower phase syconia, indicating that E. altissima and Eupristina sp. can distinguish female flower phase syconia of Ficus altissima from the male one, and keep away from the male phase syconia in order to quickly localized its female host. Observation showed there are differences responses to fig volatiles of the other developmental phase between two wasp species. E. altissima significantly repelled to the fig volatiles of pre-female phase and post-pollinated or oviposited phase, while Eupristina sp. showed no significant preference between them, which indicated that E. altissima was able to recognize the syconia of pre-female phase and post-pollinated or oviposited phase and avoid entering into them, while Eupristina sp. can not. (2) E. altissima and Eupristina sp. also showed similary responses to infochemicals linalool, benzyl ethylene The interation of benzyl ethylene and farnesol significantly affected the choice behavior of both the two wasp species. Both wasp species repelled mix infochemicals of group A₁B₂C₂(0.5% Linalool+1% Benzyl ethylene+1% Farnesol) significantly and significantly attracted by mix infochmicals of group A₂B₁C₁(1% Linalool+0.5% Benzyl ethylene+0.5% Farnesol), A₂B₁C₂(1% Linalool+0.5% Benzyl ethylene+1% Farnesol), A₂B₂C₁(1% Linalool+1% Benzyl ethylene+0.5% Farnesol), while two wasp species showed difference responses to mix infochemical of group A₁B₁C₁(0.5% Linalool+0.5% Benzyl ethylene+0.5% Farnesol). Above all, the two different wasp species can discriminate different volatile signals, and E. altissima was more favor to the fig volatiles of their host than Eupristina sp., therefore, E. altissima was able to locate their host more accurately than Eupristina sp. The different responses of E. altissima and Eupristina sp. to the fig volatiles and infochemicals may related to the different structure of their antenna. Our result will provide a scientific basis to the studies of chemical signaling mechanism of fig-wasp mutualism.