榕树雄花期果内信息化学物质的时空异质性与功能分化

Understanding the ecological determinants of community structure and functional division is one of the key issues in ecology today, particularly transmission of information linked chemical cues and physiological aspects among different insect groups. Relationship between Ficus spp (Moraceae) and their associated fig wasps has been recognized as a convenient model to test the hypotheses of spatiotemporal heterogeneity and functioning of semiochemical among these functional groups, including mutualistic pollinators, gall-makers, inquiline and parasitoids, all of which develop within individual galls and attain sexual maturity simultaneously within the enclosed cavity of the fig. Specially, Males carry the specific burden of detecting and opening mating holes in galls containing conspecific females before mating with them. According to the principle of chemical ecology and bioinformatics, we will investigate the cuticular hydrocarbon profiles, gall volatiles, pollen odors as well as chemoreceptor sequences by using of GC-MS method and molecular biology techniques in four consecutive years, respectively. We also conduct behavioral experiments, like as two-choice and electrophysiological methods, to test how response wasp receive differential chemical components. Further, we also analyze niche overlap and partition of female gall resource that may be occupied by females or males of multiple fig wasp species. Since fig wasps have extreme sexual dimorphisms that reflect the different activities of females and males. Therefore, our results will be beneficial to explain the semiochemical diversity and chemical mediation among different fig wasps in the enclosed cavity. Finally, these results will reveal heterogeneity and functional partition of semiochemicals in male-floral fig. In conclusion, this study will help us to catch on the mechanisms for semiochemical adaptations and acceptance in order to better understand the mate recognition and reproductive behavior. We also discuss the coexisting and mutual relationships in fig-associated wasp community.

解析群落结构和功能是当今生态学研究的重要组成部分，化学通讯在昆虫群落结构组成和功能分化中起着重要作用。本项目从不同传粉模式的雄花期榕果内传粉者、造瘿者、寄生者所组成榕小蜂群落的功能分化出发，以榕小蜂觅偶、交配和采粉行为的化学通讯为切入点，以驱动行为本质的两个核心因子——信息化学物质和信息受体为主要研究内容，以解释果内榕小蜂求偶行为和繁殖行为为重点，运用行为学、化学生态学、电生理学和生物信息测定的方法，结合榕小蜂配偶识别、种内交配、种间羽化时序及主被动传粉的特征，连续4年研究雄花期果内信息化学物质的多样性和利用模式，阐明果内信息化学物质的时空异质性和功能分化，揭示榕小蜂果内行为产生的信息适应与接受机理，为探讨榕树-榕小蜂共生系统维持机制提供新视野。

榕蜂繁殖共生体是榕小蜂与榕树因营养级联而形成的多功能群落，被认为是研究群落组装与驱动机制的优良模型。研究以雄花期榕果内传粉者、造瘿者、寄生者所组成榕小蜂群落为研究对象，重点解析两个核心驱动因子-榕小蜂信息化学物质和信息受体，进而明确榕小蜂信息化学物质的多样性和利用模式。结果表明：（1）单果内寄生的鸡嗉子榕小蜂一般有3种或4种，占比分别为37.06%或35.53%，以传粉者窝榕小蜂、寄生者伪鞘榕小蜂和寄居者拉长鞘榕小蜂最为常见，但每种榕小蜂的种群数量有巨大差异，每种榕小蜂所占用的瘿花具有明显的空间层次性，其中传粉者窝榕小蜂位于最外层，而非传粉榕小蜂则位于中下层，每种雄蜂均比同种雌蜂更靠近外层，反映了榕小蜂在寄生与生态位方面存在进化约束；（2）不同榕小蜂体表碳氢化合物的种类不同，但均包括正链烷烃、甲基烷烃、烯烃和甲基烯烃4类，且物种和性别间的化合物种类、数量、时间及空间分布上均有着明显的差异，Squalene和2-Me-C28为共有化合物，含量上的差异使其能够作为候选性信息素；（3）4种榕树花粉气味具有较高的多样性，methyl salicylate、n-c13、β-elemene、methylcyclopentane、dibutyl phthalate、nonanal、acetoin、α-pinene、cosmene、β-phellandrene和β-selinene是主要成分，且榕树花粉挥发物具有强烈的物种特异性，主、被动授粉模式下（或雌雄同株、异株）榕树花粉气味的构成特征具有明显的差异（R>0，P<0.01）；（4）窝榕小蜂、妃延腹榕小蜂、伪鞘榕小蜂、钝叶榕传粉榕小蜂Eupristina sp.、杨氏金小蜂和Lipothymus sp．分别鉴定出13、57、56、8、27和56个OBPs以及5、15、11、11、9和22个CSPs，在触角、头、胸、腹和卵巢等组织均存在特异性表达基因，同时产卵的榕小蜂受到纯化选择，而后产卵者则受到正选择压力；（5）分子对接显示窝榕小蜂和佩妃延腹榕小蜂的OBPs和CSPs通过氢键与活性成分互作，而伪鞘榕小蜂则通过疏水作用力固定在结合腔内。