Phillips R D, Bohman B, Anthony J M, Krauss S L, Dixon K W, Peakall R
Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, ACT, 0200, Australia; Kings Park and Botanic Garden, The Botanic Garden and Parks Authority, West Perth, 6005, Western Australia, Australia; School of Plant Biology, The University of Western Australia, Nedlands, 6009, Western Australia, Australia.
J Evol Biol. 2015 Mar;28(3):601-12. doi: 10.1111/jeb.12593. Epub 2015 Feb 20.
Plants are predicted to show floral adaptation to geographic variation in the most effective pollinator, potentially leading to reproductive isolation and genetic divergence. Many sexually deceptive orchids attract just a single pollinator species, limiting opportunities to experimentally investigate pollinator switching. Here, we investigate Drakaea concolor, which attracts two pollinator species. Using pollinator choice tests, we detected two morphologically similar ecotypes within D. concolor. The common ecotype only attracted Zaspilothynnus gilesi, whereas the rare ecotype also attracted an undescribed species of Pogonothynnus. The rare ecotype occurred at populations nested within the distribution of the common ecotype, with no evidence of ecotypes occurring sympatrically. Surveying for pollinators at over 100 sites revealed that ecotype identity was not correlated with wasp availability, with most orchid populations only attracting the rare Z. gilesi. Using microsatellite markers, genetic differentiation among populations was very low (GST = 0.011) regardless of ecotype, suggestive of frequent gene flow. Taken together, these results may indicate that the ability to attract Pogonothynnus has evolved recently, but this ecotype is yet to spread. The nested distribution of ecotypes, rather than the more typical formation of ecotypes in allopatry, illustrates that in sexually deceptive orchids, pollinator switching could occur throughout a species' range, resulting from multiple potentially suitable but unexploited pollinators occurring in sympatry. This unusual case of sympatric pollinators highlights D. concolor as a promising study system for further understanding the process of pollinator switching from ecological, chemical and genetic perspectives.
据预测，植物会针对最有效的传粉者的地理差异表现出花部适应性，这可能导致生殖隔离和遗传分化。许多具有性欺骗性的兰花只吸引单一传粉者物种，限制了通过实验研究传粉者转换的机会。在此，我们研究了吸引两种传粉者物种的同色兜兰（Drakaea concolor）。通过传粉者选择测试，我们在同色兜兰中检测到两种形态相似的生态型。常见生态型只吸引吉氏窄腹胡蜂（Zaspilothynnus gilesi），而罕见生态型还吸引了一种未描述的原腹胡蜂属（Pogonothynnus）物种。罕见生态型出现在嵌套于常见生态型分布范围内的种群中，没有证据表明生态型会同域出现。在100多个地点对传粉者进行调查发现，生态型特征与胡蜂的可获得性无关，大多数兰花种群只吸引罕见的吉氏窄腹胡蜂。使用微卫星标记，无论生态型如何，种群间的遗传分化都非常低（GST = 0.011），这表明基因流频繁。综合来看，这些结果可能表明吸引原腹胡蜂属的能力是最近才进化出来的，但这种生态型尚未扩散。生态型的嵌套分布，而非异地更典型的生态型形成方式，说明在具有性欺骗性的兰花中，可以在一个物种的整个分布范围内发生传粉者转换，这是由于同域存在多种潜在合适但未被利用的传粉者。这种同域传粉者的不寻常案例突出了同色兜兰作为一个有前景的研究系统，可从生态、化学和遗传角度进一步了解传粉者转换过程。
