榕果挥发物对传粉榕小蜂的吸引作用

榕树 /榕小蜂专一性共生系统的维持 ,与榕树开花期释放的特殊的挥发性化合物以及榕小蜂对其寄主榕树的化学识别和定位紧密相关。研究选取了西双版纳地区常见的 3种榕树 ,即对叶榕 Ficus hispida、木瓜榕 F.auriculata和鸡嗉子榕F.semicordata的榕果作为实验材料 ,利用野外诱捕实验、室内生物检测实验检测传粉榕小蜂 Hymenoptera:ChalcidoidaeAgaonidae对 12种信息化合物及榕果的二氯甲烷浸提物的趋向性反应 ,研究不同榕属植物的传粉榕小蜂对相同的信息化合物的反应差异 ,以及传粉榕小蜂受不同发育时期榕果浸提物吸引的显著性程度。诱捕实验中对叶榕小蜂 Ceratosolen solmsimarchali对香叶醇的趋向性反应显著 ,大果榕小蜂 C.emarginatus对接受期榕果浸提物和芳樟醇都有明显的趋向性反应 ,而对间花期榕果浸提物则无显著反应。嗅觉仪生物检测实验中 ,鸡嗉果榕小蜂 C.gravelyi对香叶醇和松油醇都表现出显著的趋向性反应。结果表明 ,对叶榕、鸡嗉子榕传粉榕小蜂对 12种信息化合物的反应存在一定的差异 ,木瓜榕传粉榕小蜂对香叶醇和木瓜榕接受期榕果浸提物的趋向性反应比间花期榕果强得多

Chemical attraction of fig volatiles to their pollinating fig wasps

The specificity of the relationship between fig species and their particular agaonine pollinators (Hymenoptera: Chalcidoidea Agaonidae) has long been regarded as the extreme example of co-evolution. 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 or pollinate for their partners.Field assay and olfactometry experiments were designed to examine the chemical basis of the species-specific mutualism and the difference between receptive fig volatiles and non-receptive ones in attracting pollinators. Three tropical fig species: Ficus hispida, F.auriculata and F.semicordata, and their corresponding pollinating fig wasps Ceratosolen solmsi marchali, (C. emarginatus) and C.gravelyi were chosen for tests. Fig volatiles including 12 info-chemicals and 3 dichloromethane extracts of figs in receptive and inter-floral phases were tested. The field experiments were conducted in Xishuangbanna Tropical Botanical Garden in Yunnan province of China. Sticky traps with cotton balls contained 0.5ml solvent or fig volatile compounds were set near fig trees of F. hispida and (F. auriculata) in male phase. Every day at 12:00 and 18:00, the numbers of fig wasps in each trap were recorded. Each observation lasted 2 weeks. Data were analyzed by the Mann-Whitney U test. The results showed that geraniol was significantly attractive to C. solmsi marchali (p<0.05), while vanillin and linalool were attractive in lesser degrees only (p<0.10). Linalool and the extract of receptive figs of F. auriculata were significantly attractive to C. emarginatus, but the number of the wasps trapped by the inter-floral fig extract was even lower than the control. Furthermore, a four-arm olfactometer was used to test the responses of the pollinating fig wasps to 12 fig volatile compounds. The wasps trapped in the arm treated with volatile compound and in the control arm were recorded respectively. Data were analyzed by a paired t-test. The results showed that C. gravelyi were significantly attracted by geraniol and terpineol (p<0.05). The responses of C.solmsi marchali and C.gravelyi to 12 info-chemicals were different, but they both preferred geraniol, linalool, farnesol, vanillin and terpineol to other compounds. C.emarginatus showed greater preference for the receptive fig extracts than the inter-floral ones.The results suggest that the fig-fig wasp specificity might result from the specific combination of several major fig volatile compounds and some particular minor volatile compounds. The results also indicate that pollinating fig wasps have preferences for receptive figs.