Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
Department of Biology, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada.
New Phytol. 2022 Dec;236(5):1908-1921. doi: 10.1111/nph.18335. Epub 2022 Jul 12.
Fully mycoheterotrophic plants can be difficult to place in plant phylogeny due to elevated substitution rates associated with photosynthesis loss. This potentially limits the effectiveness of downstream analyses of mycoheterotrophy that depend on accurate phylogenetic inference. Although mitochondrial genomic data sets are rarely used in plant phylogenetics, theory predicts that they should be resilient to long-branch artefacts, thanks to their generally slow evolution, coupled with limited rate elevation in heterotrophs. We examined the utility of mitochondrial genomes for resolving contentious higher-order placements of mycoheterotrophic lineages in two test cases: monocots (focusing on Dioscoreales) and Ericaceae. We find Thismiaceae to be distantly related to Burmanniaceae in the monocot order Dioscoreales, conflicting with current classification schemes based on few gene data sets. We confirm that the unusual Afrothismia is related to Taccaceae-Thismiaceae, with a corresponding independent loss of photosynthesis. In Ericaceae we recovered the first well supported relationships among its five major lineages: mycoheterotrophic Ericaceae are not monophyletic, as pyroloids are inferred to be sister to core Ericaceae, and monotropoids to arbutoids. Genes recovered from mitochondrial genomes collectively resolved previously ambiguous mycoheterotroph higher-order relationships. We propose that mitochondrial genomic data should be considered in standardised gene panels for inferring overall plant phylogeny.
由于与光合作用丧失相关的高替代率，完全菌根异养植物在植物系统发育中可能难以定位。这可能限制了依赖准确系统发育推断的菌根异养下游分析的有效性。尽管线粒体基因组数据集在植物系统发育学中很少使用，但理论预测，由于其进化缓慢，加上异养生物的速率升高有限，它们应该能够抵抗长枝伪像。我们在两个测试案例中检查了线粒体基因组对于解决有争议的菌根异养谱系高级阶元定位的有用性：单子叶植物（专注于薯蓣目）和杜鹃花科。我们发现，在单子叶植物薯蓣目中，Thismiaceae 与 Burmanniaceae 远亲，这与基于少数基因数据集的当前分类方案相矛盾。我们证实，不寻常的 Afrothismia 与 Taccaceae-Thismiaceae 有关，具有相应的光合作用独立丧失。在杜鹃花科中，我们恢复了其五个主要谱系之间的第一个支持良好的关系：菌根异养杜鹃花科不是单系的，因为推测 pyroloids 与核心杜鹃花科是姐妹关系，而 monotropoids 与 arbutoids 是姐妹关系。线粒体基因组中回收的基因共同解决了以前模糊的菌根异养高级阶元关系。我们建议在推断植物总体系统发育的标准基因面板中应考虑线粒体基因组数据。
