Institute of Plant Sciences, University of Graz, Holteigasse 6, A-8010 Graz, Austria.
Mol Phylogenet Evol. 2011 Jun;59(3):603-14. doi: 10.1016/j.ympev.2011.03.021. Epub 2011 Mar 30.
Lichens are a prominent feature of northern conifer forests and a large number of species are thought to be circumboreal. Whether or not circumboreal lichen species really constitute monophyletic groups has seldom been tested. We investigated molecular phylogenetic patterns in the mycobiont of Mycoblastus sanguinarius, a well known epiphytic lichen species of the boreal forest, based on material collected from across the high latitude northern hemisphere. A three-locus dataset of internal transcribed spacer rDNA, translation elongation factor 1-α and replication licensing factor Mcm7 DNA sequences revealed that material treated until now as belonging to M. sanguinarius does indeed form a monophyletic group within the genus and is distinct from a strongly supported Mycoblastus affinis. The M. sanguinarius complex appears closely related to the rare Mycoblastus glabrescens, which is currently known only from the Pacific Northwest and was rediscovered during the present study. However, within M. sanguinarius s.lat. in the northern hemisphere, two deeply divergent and morphologically coherent species can be recovered, one of which matches the southern hemisphere species Mycoblastus sanguinarioides and turns out to be widespread in North America and Asia, and one of which corresponds to M. sanguinarius s.str. Both M. sanguinarius and M. sanguinarioides exhibit additional low-level genetic differentiation into geographically structured clades, the most prominent of which are distributed in East Asia/eastern North America and western North America/Europe, respectively. Individuals from these lowest-level clades are morphologically indistinguishable but chemical analyses by thin layer chromatography revealed that each clade possesses its own fatty acid profile, suggesting that chemical differentiation precedes morphological differentiation and may be a precursor to speciation.
地衣是北方针叶林的主要特征，大量物种被认为是环绕北极分布的。环绕北极分布的地衣物种是否真的构成单系群，这一点很少得到检验。我们基于横跨高纬度北半球采集的材料，研究了血红红衣属地衣（Mycoblastus sanguinarius）的共生真菌的分子系统发育模式。血红红衣属地衣是一种广布于北方森林的著名附生地衣，其核糖体基因内转录间隔区（ITS）、翻译延伸因子 1-α 和复制许可因子 Mcm7 的三基因座数据集显示，迄今为止被视为血红红衣属地衣的材料确实在属内形成了一个单系群，与强烈支持的亲缘关系密切的 Mycoblastus affinis 不同。血红红衣属地衣复合体与罕见的 Mycoblastus glabrescens 关系密切，后者目前仅在太平洋西北地区发现，也是在本研究中重新发现的。然而，在北半球的血红红衣属地衣复合体中，可以恢复到两个深度分歧且形态上一致的物种，其中一个与南半球的 Mycoblastus sanguinarioides 相匹配，结果证明它广泛分布于北美洲和亚洲，另一个与 Mycoblastus sanguinarius s.str. 相匹配。在北半球，血红红衣属地衣和 Mycoblastus sanguinarioides 都表现出额外的低水平遗传分化，形成地理结构的分支，其中最显著的分布在东亚/北美东部和北美西部/欧洲。这些最低水平分支的个体在形态上无法区分，但薄层色谱化学分析显示，每个分支都有自己的脂肪酸图谱，这表明化学分化先于形态分化，可能是物种形成的前兆。
