Data from: Evolutionary relationships among pollinators and repeated pollinator sharing in sexually deceptive orchids

The mechanism of pollinator attraction is predicted to strongly influence both plant diversification and the extent of pollinator sharing between species. Sexually deceptive orchids rely on mimicry of species specific sex pheromones to attract their insect pollinators. Given that sex pheromones tend to be conserved among related species, we predicted that in sexually deceptive orchids (i) pollinator sharing is rare (ii) closely related orchids use closely related pollinators (iii) there is strong bias in the wasp lineages exploited by orchids. We focused on species that are pollinated by sexual deception of thynnine wasps in the distantly related genera Caladenia and Drakaea, including new field observations for 45 species of Caladenia. Specialization was extreme with most orchids using a single pollinator species. Unexpectedly, seven cases of pollinator sharing were found, including two between Caladenia and Drakaea, which exhibit strikingly different floral morphology. Phylogenetic analysis of pollinators using four nuclear sequence loci demonstrated that while orchids within major clades primarily use closely related pollinator species, up to 17% of orchids within these clades are pollinated by a member of a phylogenetically distant wasp genus. Further, compared to the total diversity of thynnine wasps within the study region, orchids show a strong bias towards exploiting certain genera. While these patterns may arise through conservatism in the chemical classes used in sex pheromones, apparent switches between wasp clades suggest unexpected flexibility in floral semio-chemical production. Alternatively, wasp sex pheromones within lineages may exhibit greater chemical diversity than currently appreciated.

传粉者吸引机制被认为会显著影响植物的物种分化以及不同物种间传粉者共享的程度。具有性欺骗策略的兰科植物（sexually deceptive orchids）通过模拟物种特异性性信息素（species-specific sex pheromones）来吸引其昆虫传粉者。鉴于性信息素在近缘物种间往往较为保守，我们推测此类性欺骗兰科植物会呈现以下特征：(1) 传粉者共享事件较为罕见；(2) 近缘兰科植物会使用近缘的传粉者；(3) 兰科植物对胡蜂类群的利用存在显著偏向性。本研究聚焦于两个远缘属——指兰属（Caladenia）与锤兰属（Drakaea）中，通过模拟臀胡蜂亚科（thynnine wasps）性信息素实现传粉的物种，其中包含针对45种指兰属植物的全新野外观测数据。研究发现兰科植物的传粉特化程度极高，绝大多数物种仅依赖单一传粉者物种。出乎意料的是，本次研究共记录到7起传粉者共享事件，其中2起发生在指兰属与锤兰属之间，而这两个属的花部形态存在显著差异。基于4个核基因座（nuclear sequence loci）的传粉者系统发育分析显示：尽管属于主要演化支（clade）的兰科植物主要使用近缘的传粉者物种，但这些演化支中最高可达17%的兰科植物，其传粉者来自系统发育距离较远的胡蜂属。此外，相较于研究区域内臀胡蜂亚科的总物种多样性，兰科植物对胡蜂属的利用呈现出显著偏向性。尽管这些模式可能源于性信息素所使用的化学类群的保守性，但胡蜂演化支间的明显转换现象，表明兰科植物的花部信息化合物（semiochemical）合成存在出人意料的灵活性。或者，不同演化支内胡蜂的性信息素可能比当前认知中具有更高的化学多样性。