Phillips R D, Brown G R, Dixon K W, Hayes C, Linde C C, Peakall R
Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, ACT, Australia.
Kings Park and Botanic Garden, The Botanic Garden and Parks Authority, West Perth, WA, Australia.
J Evol Biol. 2017 Sep;30(9):1674-1691. doi: 10.1111/jeb.13125. Epub 2017 Jul 17.
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 and (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 although 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. Although these patterns may arise through conservatism in the chemical classes used in sex pheromones, apparent switches between wasp clades suggest unexpected flexibility in floral semiochemical production. Alternatively, wasp sex pheromones within lineages may exhibit greater chemical diversity than currently appreciated.
传粉者吸引机制预计会对植物多样化以及物种间传粉者共享程度产生强烈影响。性欺骗兰花依靠模仿物种特异性性信息素来吸引其昆虫传粉者。鉴于性信息素在相关物种中往往具有保守性，我们预测在性欺骗兰花中，（i）传粉者共享情况罕见，（ii）亲缘关系相近的兰花利用亲缘关系相近的传粉者，并且（iii）兰花所利用的胡蜂谱系存在强烈偏向性。我们聚焦于由遥远相关属的细腰蜂性欺骗传粉的物种，包括在卡拉德尼亚属的45个物种上进行的新的野外观察。专业化程度极高，大多数兰花仅使用单一传粉者物种。出乎意料的是，发现了7例传粉者共享情况，包括卡拉德尼亚属和德拉克亚属之间的两例，这两个属展现出显著不同的花形态。利用四个核序列位点对传粉者进行的系统发育分析表明，尽管主要分支内的兰花主要利用亲缘关系相近的传粉者物种，但这些分支内高达17%的兰花由系统发育上遥远的胡蜂属的成员传粉。此外，与研究区域内细腰蜂的总多样性相比，兰花在利用某些属方面表现出强烈偏向性。尽管这些模式可能是由于性信息素中所使用化学类别上的保守性而产生的，但胡蜂分支之间明显的转变表明在花的信息化学物质产生方面存在意想不到的灵活性。或者，谱系内的胡蜂性信息素可能表现出比目前所认识到的更大的化学多样性。
