鸡嗉子榕传粉榕小蜂表皮碳氢化合物的性二型及季节变化

Sexual dimorphism and seasonal variations in cuticular hydrocarbons of the pollinating fig wasp in Ficus semicordata

生存与繁殖对生物体维持和延续种群数量稳定至关重要。表皮碳氢化合物具有维持昆虫水分平衡和信息通讯的双重功能,目前对于昆虫在不同气候条件下如何权衡防脱水与保持化学信号可靠性的潜在冲突尚不清楚。本文以寄生于鸡嗉子榕(Ficus semicordata)雄花期果内的传粉榕小蜂窝榕小蜂(Ceratosolen gravelyi)为研究对象,利用气相色谱-质谱联用仪(GC-MS)解析雨季、雾凉季和干热季中雌、雄成虫表皮碳氢化合物的种类及含量,运用非度量多维尺度排序、相似性分析、置换多元方差分析和随机森林等方法分析了窝榕小蜂表皮碳氢化合物对不同季节变化的响应机制。结果表明:(1)窝榕小蜂表皮碳氢化合物由34种C7–C44的化合物组成,包括正链烷烃、甲基烷烃、烯烃和甲基烯烃;其中角鲨烯(squalene)、2-甲基二十八烷(2-Me-C28)、正三十四烷(n-C34)、正三十六烷(n-C36)和正四十四烷(n-C44)为主要成分(>5%)。(2)不同性别窝榕小蜂表皮碳氢化合物的组成及含量存在显著差异,正四十二烷(n-C42)、17-三十五烯(17-C35:1)、1-二十九烯(C29:1)、2-Me-C28和角鲨烯是造成两性差异的重要贡献量化合物。(3)雌、雄成虫表皮碳氢化合物均具有明显的季节变化:在干热季中,雌蜂正链烷烃(n-C34、n-C36和n-C44)的比例及碳氢化合物的总绝对含量增加,2-Me-C28和角鲨烯的比例降低;雄蜂甲基烯烃的比例增加,正链烷烃和甲基烷烃的比例降低,碳氢化合物总绝对含量无明显变化。本研究发现窝榕小蜂表皮碳氢化合物具有明显的性二型和强烈的季节可塑性,2-Me-C28和角鲨烯可作为雄蜂配偶识别时的候选性信息素;雌、雄成虫在适应高温和/或干燥的气候条件时存在差异化响应,表明窝榕小蜂两性表皮碳氢化合物在不同季节变化中采取不同的适应性策略。本研究揭示了榕小蜂应对不同气候环境的化学适应机制,为研究昆虫双重性状和理解生态适应与物种形成之间的功能联系奠定了化学基础。

Aims:Survival and reproduction are fundamental traits crucial for maintaining population stability in organisms.Cuticular hydrocarbons serve dual purposes in insects:maintaining water balance and facilitating chemical communication.However,the interplay between adaptation to varying climatic conditions and maintaining reliability in chemical signaling remains poorly understood.This study delves into the sexual dimorphism and seasonal variations in cuticular hydrocarbons of the pollinating fig wasp Ceratosolen gravelyi,which parasitizes the male phase of Ficus semicordata.Methods:Gas chromatography-mass spectrometry(GC-MS)was employed to analyze the types and concentrations of cuticular hydrocarbons present in female and male adults of C.gravelyi across distinct seasonal periods:rainy,fog-cool,and dry-hot seasons.To elucidate the response mechanism of cuticular hydrocarbons in C.gravelyi to varying seasons,non-metric multidimensional scaling,analysis of similarities,permutational multivariate analysis of variance,and random forest techniques were utilized.Results:(1)A total of 34 compounds were identified in the cuticular hydrocarbons produced by the pollinator C.gravelyi in F.semicordata,primarily comprising n-alkanes,methylalkanes,olefins,and methylolefins,with carbon chain lengths ranging from C7 and C44.Notably,squalene,2-Methyloctacosane(2-Me-C28),n-Tetratriacontane(n-C34),n-Hexatriacontane(n-C36),and n-Tetratetracontane(n-C44)emerged as the predominant components,each constituting over 5%of the total composition.(2)Significant qualitative and quantitative differences were observed in the cuticular hydrocarbon profiles between male and female adults of C.gravelyi.Notable contributors to these differences included n-Dotetracontane(n-C42),17-Pentatriacontene(17-C35:1),1-Nonacosene(C29:1),2-Me-C28,and squalene.(3)The cuticular hydrocarbons of both male and female adults exhibited pronounced seasonal variations.During the dry-hot season,there was a notable increase in the proportion of n-alkanes(n-C34,n-C36,and n-C44)and the total absolute content of cuticular hydrocarbons in females.This increase was accompanied by a decrease in the proportion of methylalkanes(2-Me-C28)and methylalkenes(squalene).Conversely,in males,there was an increase in the proportion of methylalkenes,while the proportions of n-alkanes and methylalkanes decreased.However,the total absolute content of cuticular hydrocarbons did not exhibit significant variation in males across seasons.Conclusion:This study elucidates the sexual dimorphism and seasonal plasticity inherent in the cuticular hydrocarbons of C.gravelyi.Specifically,2-Me-C28 and squalene emerge as potential candidate sex pheromones facilitating mate recognition among fig wasps.Our findings reveal distinct responses to high temperature and/or dry climate conditions in female and male adults,underscoring the adoption of different adaptive strategies by the two sexes of the pollinator C.gravelyi across seasons.This research sheds light on the chemical adaptation mechanism of fig wasps to varying climatic environments,laying a foundational understanding of the ecological and evolutionary implications of cuticular hydrocarbons.These insights provide a crucial chemical framework for studying the dual traits of insects and unraveling the functional relationship between ecological adaptation and speciation.