Lineage and role in integrative taxonomy of a heterotrophic orchid complex

Lineage-based species definitions applying coalescent approaches to species delimitation have become increasingly popular. Yet, the application of these methods and the recognition of lineage-only definitions have recently been questioned. Species delimitation criteria that explicitly consider both lineages and evidence for ecological ‘role’ shifts provide an opportunity to incorporate ecologically meaningful data from multiple sources in studies of species boundaries. Here, such criteria were applied to a problematic group of mycoheterotrophic orchids, the <em>Corallorhiza striata</em> complex, analyzing genomic, morphological, phenological, reproductive-mode, niche, and fungal host data. A recently developed method for generating genomic polymorphism data–ISSRseq–demonstrates evidence for four distinct lineages, including a previously unidentified lineage in the Coast Ranges and Cascades of California and Oregon, USA. There is divergence in morphology, phenology, reproductive mode, and fungal associates among the four lineages. Integrative analyses, conducted in population assignment and redundancy analysis frameworks, provide evidence of distinct genomic lineages and a similar pattern of divergence in the ‘extended’ data, albeit with weaker signal. However, none of the ‘extended’ datasets fully satisfy the condition of a significant ‘role’ shift, which requires evidence of fixed differences. The four lineages identified in the current study are recognized at the level of variety, short of comprising different species. This study represents the most comprehensive application of ‘lineage+role’ to date and illustrates the advantages of such an approach.采用溯祖分析方法开展物种界定的基于谱系的物种定义范式，近年来愈发流行。然而，此类方法的应用以及仅基于谱系的定义的认可度，近期遭到了质疑。那些同时明确考量谱系与生态‘角色’转变证据的物种界定标准，为在物种边界研究中纳入多源生态意义数据提供了契机。本研究将此类标准应用于一类存在分类争议的菌异养兰科植物——条纹珊瑚兰（*Corallorhiza striata*）复合群，分析了基因组、形态学、物候学、繁殖方式、生态位以及真菌宿主数据。一种新近开发的基因组多态性数据生成方法——ISSR测序（ISSRseq）——证实存在四个独立谱系，其中包括此前未被发现的、分布于美国加利福尼亚州与俄勒冈州海岸山脉及喀斯喀特山脉的谱系。四个谱系在形态学、物候学、繁殖方式以及真菌共生伙伴方面均存在分化。基于群体遗传聚类与冗余分析框架开展的整合分析，不仅证实了独立基因组谱系的存在，同时在“扩展”数据集上也呈现出相似的分化模式，只是信号强度较弱。然而，所有“扩展”数据集均未完全满足显著“角色”转变的条件——该条件要求存在固定差异的证据。本研究鉴定出的四个谱系，目前仅被认定为变种等级，尚未达到物种级别。本研究是迄今为止对“谱系+角色”整合范式最为全面的应用，并阐明了此类研究方法的优势。