Bateman Richard M, Rudall Paula J, Bidartondo Martin I, Cozzolino Salvatore, Tranchida-Lombardo Valentina, Carine Mark A, Moura Mónica
Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3AB, UK.
Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3AB, UK Imperial College London, London, SW7 2AZ, UK.
Am J Bot. 2014 Jun 1;101(6):979-1001. doi: 10.3732/ajb.1300430. Epub 2014 Jun 6.
• Premise of the study: Most orchid species native to the Macaronesian islands reflect immigration from western Europe or North Africa followed by anagenesis. The only putative exception is the butterfly orchids (Platanthera) of the Azores, where three species apparently reflect at least one cladogenetic speciation event. This multidisciplinary study explores the origin, speciation, phenotypic, and genotypic cohesion of these Azorean species and their mainland relatives.• Methods: Plants of Platanthera from 30 localities spanning all nine Azorean islands were compared with those of four continental European relatives for 38 morphometric characters; substantial subsets were also analyzed for plastid microsatellites, and for nrITS of both the orchids and their mycorrhizae.• Key results: Although the three Azorean and four mainland species are all readily distinguished morphometrically using several floral characters, and hybridization appears rare, divergence in ITS and especially plastid sequences is small. Despite occupying similar laurisilva habitats, the Azorean species differ radically in the identities and diversity of their mycorrhizal partners; specialism apparently increases rarity.• Conclusions: Although morphological evidence suggests two invasions of the islands from NW Africa and/or SW Europe, ITS data imply only one. As the molecular data are unable to distinguish among the potential mainland ancestors, two scenarios of relationship are explored that imply different ancestors. Both scenarios require both anagenetic and cladogenetic speciation events, involving homoplastic shifts in overall flower size and (often substantial) changes in the relative dimensions of individual floral organs. Limited genotypic divergence among the three species compared with greater phenotypic divergence suggests comparatively recent speciation. Mycorrhizae may be the most critical factor dictating the respective ecological tolerances, and thus the relative frequencies, of these species. The recent IUCN Red-List amalgamation of Azorean Platanthera taxa into a single species urgently requires reappraisal, as P. micrantha is an excellent indicator species of seminatural laurisilva forest and P. azorica is arguably Europe's rarest orchid.
• 研究前提：马卡罗尼西亚群岛的大多数本土兰花物种反映了从西欧或北非的迁入，随后是前进演化。唯一可能的例外是亚速尔群岛的蝶兰属（Platanthera），其中三个物种显然反映了至少一次分支进化物种形成事件。这项多学科研究探讨了这些亚速尔群岛物种及其大陆近缘种的起源、物种形成、表型和基因型凝聚力。
• 方法：对来自亚速尔群岛所有九个岛屿的30个地点的Platanthera植物与四个欧洲大陆近缘种的植物进行了38个形态测量特征的比较；还对大量亚组进行了质体微卫星分析，以及对兰花及其菌根的nrITS进行了分析。
• 主要结果：尽管三个亚速尔群岛物种和四个大陆物种都可以通过几个花部特征在形态测量上很容易地区分开来，而且杂交似乎很少见，但ITS尤其是质体序列的差异很小。尽管占据了相似的月桂树林栖息地，但亚速尔群岛物种的菌根伙伴的身份和多样性却有很大差异；专一性显然增加了稀有性。
• 结论：尽管形态学证据表明该岛有两次来自西北非洲和/或西南欧洲的入侵，但ITS数据仅表明有一次。由于分子数据无法区分潜在的大陆祖先，因此探讨了两种关系情景，这意味着不同的祖先。两种情景都需要前进演化和分支进化物种形成事件，包括总体花大小的同塑性变化以及单个花器官相对尺寸的（通常是显著的）变化。与更大的表型差异相比，这三个物种之间有限的基因型差异表明物种形成相对较新。菌根可能是决定这些物种各自生态耐受性以及相对频率的最关键因素。国际自然保护联盟（IUCN）最近将亚速尔群岛Platanthera分类群合并为一个物种的做法迫切需要重新评估，因为小花Platanthera micrantha是半天然月桂树林地的优秀指示物种，而亚速尔Platanthera azorica可以说是欧洲最稀有的兰花。
