Lichens provide valuable systems for studying symbiotic interactions. In lichens, these interactions are frequently described in terms of availability, selectivity and specificity of the mycobionts and photobionts towards one another. The lichen-forming, green algal genus Trebouxia Puymaly is among the most widespread photobiont, associating with a broad range of lichen-forming fungi. To date, 29 species have been described, but studies consistently indicate that the vast majority of species-level lineages still lack formal description, and new, previously unrecognized lineages are frequently reported. To reappraise the diversity and the evolutionary relationships of species-level lineages in Trebouxia, we assembled DNA sequence data from over 1600 specimens, compiled from a range of sequences from previously published studies, axenic algal cultures, and lichens collected from poorly sampled regions. From these samples, we selected representatives of the currently known genetic diversity in the lichenized Trebouxia and inferred a phylogeny from multi-locus sequence data (ITS, rbcL, cox2). We demonstrate that the current formally described species woefully underrepresent overall species-level diversity in this important lichen-forming algal genus. We anticipate that an integrative taxonomic approach, incorporating morphological and physiological data from axenic cultures with genetic data, will be required to establish a robust, comprehensive taxonomy for Trebouxia. The data presented here provide an important impetus and reference dataset for more reliably characterizing diversity in lichenized algae and in using lichens to investigate the evolution of symbioses and holobionts.

中文翻译：

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正式描述的物种在常见的地衣光生物体Trebouxia（Trebouxiophyceae，Chlorophyta）中严重不足以代表系统发育多样性：推动了综合分类学的发展。

地衣为研究共生相互作用提供了有价值的系统。在地衣中，这些相互作用通常是根据霉菌和光生生物彼此之间的可用性，选择性和特异性来描述的。形成地衣的绿色藻属Trebouxia Puymaly属于最广泛的光生物体，与广泛的形成地衣的真菌有关。迄今为止，已经描述了29个物种，但是研究始终表明，绝大多数物种级别的谱系仍缺乏正式描述，并且经常报道新的，以前未被认识的谱系。为了重新评估Trebouxia物种级谱系的多样性和进化关系，我们收集了1600多个标本的DNA序列数据，这些数据是根据先前发表的研究中的一系列序列汇编而成的，轴距藻类培养物和地衣是从采样较差的区域收集的。从这些样本中，我们选择了地衣病性Trebouxia中目前已知的遗传多样性的代表，并从多位点序列数据（ITS，rbcL，cox2）推断出系统发育。我们证明当前正式描述的物种在这个重要的地衣形成藻类中严重不足以代表总体物种水平的多样性。我们预计，将需要一种整合的分类学方法，将树莓文化的形态学和生理学数据与遗传数据相结合，以建立针对Trebouxia的强大，全面的分类学。