Data from: Patterns of morphological and plastid DNA variation in the Corallorhiza striata species complex (Orchidaceae)

Corallorhiza striata is a wide-ranging, morphologically variable, mycoheterotrophic species complex distributed across North America. Objectives of this study were to assess relationships and test validity of previously delimited varieties of C. striata, including the recently described C. bentleyi. Two plastid DNA regions were sequenced for individuals from several populations across North America, identifying four major clades. The large-flowered C. striata var. striata (northern U.S.A., southern Canada) was sister to the smaller-flowered var. vreelandii (southwestern U.S.A., Mexico), and these were sister to a Californian clade with relatively intermediate-sized flowers. C. striata var. involuta (Mexico) and the endangered C. bentleyi (eastern U.S.A.) shared a close relationship, sister to the remaining C. striata. Principal Components Analysis and Nonparametric Multivariate Analysis of Variance on nine quantitative morphological characters, using plastid DNA clades as independent variables, demonstrated strong correlations between molecular and morphological groupings. Morphological analyses supported differentiation of both C. striata var. involuta and C. bentleyi relative to all other accessions of C. striata, suggesting their recognition as separate species; these findings will have future implications for conservation. The biogeographic scenario was more complex than previously thought, with members of two major plastid DNA lineages (C. bentleyi/var. involuta and the remaining C. striata) existing in Mexico and U.S.A./Canada. These findings contribute to a burgeoning body of data on poorly studied North American plant distributions extending into southern Mexico.

条纹珊瑚兰（Corallorhiza striata）是一个分布范围广泛、形态多样性丰富的菌异养（mycoheterotrophic）物种复合体，广泛分布于北美大陆。本研究旨在厘清该类群的亲缘关系，并验证此前划定的条纹珊瑚兰变种的有效性，其中包括近年发表描述的本特利珊瑚兰（C. bentleyi）。
研究人员对北美多个种群的个体开展了两段质体DNA（plastid DNA）区域的测序，共鉴定出四大支系。其中大花型的条纹珊瑚兰原变种（C. striata var. striata，分布于美国北部、加拿大南部）与小花型的vreelandii变种（C. striata var. vreelandii，分布于美国西南部、墨西哥）互为姐妹群，而这两个类群又与一类花大小相对居中的加州支系构成姐妹群关系。
墨西哥分布的involuta变种（C. striata var. involuta）与濒危的本特利珊瑚兰（分布于美国东部）亲缘关系紧密，二者共同构成的支系为其余条纹珊瑚兰类群的姐妹群。
研究以质体DNA支系作为自变量，对9个定量形态性状开展主成分分析（Principal Components Analysis）与非参数多元方差分析（Nonparametric Multivariate Analysis of Variance），结果显示分子聚类结果与形态分组之间存在显著相关性。
形态学分析证实，involuta变种与本特利珊瑚兰均与其他所有条纹珊瑚兰样本存在显著分化，提示应将二者认定为独立物种；该研究结果对后续植物保育工作具有重要指导意义。
本次研究揭示的生物地理演化场景较此前认知更为复杂：两大质体DNA支系（本特利珊瑚兰/involuta变种支系，以及其余条纹珊瑚兰支系）同时分布于墨西哥与美加地区。本研究的数据为针对北美（向南延伸至墨西哥南部）研究程度较低的植物分布的日益壮大的研究数据集贡献了新的内容。