Ministry of Education Key Laboratory of Biodiversity Sciences and Ecological Engineering and State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, Institute of Plant Biology, Institute of Biodiversity Sciences, Center for Evolutionary Biology, School of Life Sciences, Fudan University, 2005 Songhu Road, Shanghai 200433, China.
Boyce Thompson Institute, Ithaca, NY 14853, USA.
Mol Phylogenet Evol. 2018 Oct;127:961-977. doi: 10.1016/j.ympev.2018.06.043. Epub 2018 Jul 5.
Ferns account for 80% of nonflowering vascular plant species and are the sister lineage of seed plants. Recent molecular phylogenetics have greatly advanced understanding of fern tree of life, but relationships among some major lineages remain unclear. To better resolve the phylogenetic relationships of ferns, we generated transcriptomes from 125 ferns and two lycophytes, with three additional public datasets, to represent all 11 orders and 85% of families of ferns. Our nuclear phylogeny provides strong supports for the monophyly of all four subclasses and nearly all orders and families, and for relationships among these lineages. The only exception is Gleicheniales, which was highly supported as being paraphyletic with Dipteridaceae sister to a clade with Gleicheniaceae + Hymenophyllales. In addition, new and strongly supported phylogenetic relationships are found for suborders and families in Polypodiales. We provide the first dated fern phylogenomic tree using many nuclear genes from a large majority of families, with an estimate for separation of the ancestors of ferns and seed plants in early Devonian at ∼400 Mya and subsequent gradual divergences of fern orders from ∼380 to 200 Mya. Moreover, the newly obtained fern phylogeny provides a framework for gene family analyses, which indicate that the vast majority of transcription factor families found in seed plants were already present in the common ancestor of extant vascular plants. In addition, fern transcription factor genes show similar duplication patterns to those in seed plants, with some showing stable copy number and others displaying independent expansions in both ferns and seed plants. This study provides a robust phylogenetic and gene family evolution framework, as well as rich molecular resources for understanding the morphological and functional evolution in ferns.
蕨类植物占非开花维管植物物种的 80%,是种子植物的姊妹谱系。最近的分子系统发育学极大地提高了对蕨类植物生命之树的认识,但一些主要谱系之间的关系仍不清楚。为了更好地解析蕨类植物的系统发育关系,我们从 125 种蕨类植物和 2 种石松类植物中生成了转录组,同时还使用了另外 3 个公共数据集,代表了所有 11 个目和 85%的蕨类植物科。我们的核系统发育树为所有 4 个亚纲以及几乎所有的目和科的单系性提供了强有力的支持,也为这些谱系之间的关系提供了支持。唯一的例外是水龙骨目,它被高度支持为并系,而里白科与石松目+木贼目组成的一个分支关系最近。此外,在水龙骨目中还发现了新的、得到强有力支持的亚目和科的系统发育关系。我们提供了第一个使用来自绝大多数科的大量核基因构建的有时间标记的蕨类植物系统发育树,估计蕨类植物和种子植物的祖先在早泥盆世分离,约在 4 亿年前,随后蕨类植物目在 3.8 亿年前至 2 亿年前逐渐分化。此外,新获得的蕨类植物系统发育树为基因家族分析提供了一个框架,表明在现存维管植物的共同祖先中已经存在种子植物中发现的绝大多数转录因子家族。此外,蕨类植物的转录因子基因显示出与种子植物相似的重复模式,有些具有稳定的拷贝数,而有些则在蕨类植物和种子植物中都有独立的扩张。本研究为理解蕨类植物的形态和功能进化提供了一个稳健的系统发育和基因家族进化框架,以及丰富的分子资源。