信息化合物对薜荔榕小蜂选择行为的影响

The effect of infochemicals on selection behavior of Wiebesia pumilae ( Hymenoptera: Chalcidoidea: Agaonidae)

爱玉子和薜荔均为桑科榕属植物,与薜荔榕小蜂保持稳定的共生关系,信息化合物在维系榕树与其传粉小蜂的共生关系中起决定性作用。应用Y型嗅觉仪检测两种来源的薜荔榕小蜂对8种单一信息化合物和芳樟醇、苯甲醇和松油醇组成的混合信息化合物的趋向性反应。实验结果表明:3%和5%芳樟醇、5%的苯乙烯、7%苯甲醇、5%和7%松油醇以及7%金合欢醇对两种来源的薜荔榕小蜂均具有显著的吸引作用,7%苯甲酸甲酯对两种来源的薜荔榕小蜂有显著的趋避作用,香兰醛对两种来源的薜荔榕小蜂的行为没有显著的影响,从而表明信息化合物的种类和浓度均显著影响薜荔榕小蜂的选择行为。5%芳樟醇、3%松油醇和3%苯甲醇的混合信息化合物组合对两种来源的薜荔榕小蜂具极显著的吸引作用,信息化合物之间的交互作用极为显著。两种不同来源的薜荔榕小蜂对信息化合物反应的异同,表明两种不同来源的薜荔榕小蜂与各自宿主之间的化学通讯信号传导上存在差异,同时也表明两种不同来源的薜荔榕小蜂之间存在密切的亲缘关系。在榕树接受期花序的挥发物成分中广泛存在并占较大比例的信息化合物(例如芳樟醇),可能与榕小蜂对寄主的远程定位有关,而近距离的专性定位却是依赖于各种信息化合物严格按一定浓度、比例组成的化学图谱。实验结果为榕-蜂共生体系的化学生态学理论研究和爱玉子高产栽培提供科学依据。

Ficus awkeotsang Makino and Ficus pumila L.are both Ficus（Moraceae） species.As an endemic plant and a special fruit tree species of China,F.awkeotsang is cultivated in the south region of Yangtze River in China,whereas F.pumila is widely used in vertical greening in the garden.F.awkeotsang and F.pumila are dioecious,both of which have a stable mutualistic relationship with Wiebesia pumilae（Hymenoptera： Chalcidoidea： Agaonidae）.The maintenance of the fig-fig wasp mutualism system is strongly dependent on the chemical orientation of pollinating fig wasps using fig volatiles.The pollinating fig wasps trace the fig volatiles of their particular host and enter the figs at receptive phase（female flower phase） only,where they oviposit for themselves and meanwhile causing the plants pollinated.Infochemicals play a decisive role in maintaining the fig/pollinator mutualisms.Eight infochemicals including linalool,benzyl ethylene,benzyl alcohol,geraniol,terpineol,farnesol,vanillin and methyl benzoate were chosen for tests based on the volatile components in the recepetive phase syconia of F.awkeotsang,F.pumila and other figs.Two groups of Wiebesia pumilae from F.awkeotsang and F.pumila were tested.In this paper,the tropistic responses of two groups of Wiebesia pumilae from different sources to eight individual infochemicals and a mixture of linalool,benzyl alcohol and terpineol were measured using a Y-tube olfactometer in the laboratory.The responses of the two groups to the same infochemicals were compared.The differences in effects on the selection behavior of Wiebesia pumilae to individual and mixed infochemicals were studied.The results showed that 3% and 5% linalool,5% benzyl ethylene,7% benzyl alcohol,5% and 7% terpineol,and 7% farnesol exhibited significant attractive effect,whereas 7% methyl benzoate exhibited significant repellent effect,and vanillin exhibited little effect on both of the groups of Wiebesia pumilae,indicating that the types and concentrations of infochemicals had significant effects on the selection behavior of fig wasps,suggesting that the chemical compositions and concentrations of fig volatiles had effects on the selection behavior of their pollinator fig wasps.The results of orthogonal experiment showed that the synergistic and antagonistic effects on fig wasps were exhibited when the individual infochemicals were mixed.The mixture of 5% linalool,3% benzyl alcohol and 3% terpineol（i.e.optimum combination） exhibited extremely significant attraction to both of the groups of Wiebesia pumilae,and the interaction between different infochemicals was very significant.This further indicated that only certain compounds in a particular concentration could produce strong attractive effect on fig wasps.The similarities and differences between the responses of the two groups of Wiebesia pumilae to infochemicals suggest that the two groups of Wiebesia pumilae have a close genetic relationship between them,but may be different in the signal transduction of chemical communication between them and their hosts.The infochemicals（e.g.linalool） widely exist and account for a large proportion of the volatile components in recepetive phase syconia,which might be related to the long-range host-location of wasps.However,the short-range special host-location of wasps might be dependent on the chemical spectrum consisting of various infochemicals according to certain concentrations and proportions strictly.The results of this experiment will facilitate the theoretical study on the chemical ecology of the fig-wasp symbiosis and the high-yield cultivation of F.awkeotsang.