The ECORES Lab, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, PR China.
BMC Evol Biol. 2012 Sep 13;12:180. doi: 10.1186/1471-2148-12-180.
The fern genus Dryopteris (Dryopteridaceae) is among the most common and species rich fern genera in temperate forests in the northern hemisphere containing 225-300 species worldwide. The circumscription of Dryopteris has been controversial and various related genera have, over the time, been included in and excluded from Dryopteris. The infrageneric phylogeny has largely remained unclear, and the placement of the majority of the supraspecific taxa of Dryopteris has never been tested using molecular data.
In this study, DNA sequences of four plastid loci (rbcL gene, rps4-trnS spacer, trnL intron, trnL-F spacer) were used to reconstruct the phylogeny of Dryopteris. A total of 122 accessions are sampled in our analysis and they represent 100 species of the expanded Dryopteris including Acrophorus, Acrorumohra, Diacalpe, Dryopsis, Nothoperanema, and Peranema. All four subgenera and 19 sections currently recognized in Dryopteris s.s. are included. One species each of Arachniodes, Leptorumohra, and Lithostegia of Dryopteridaceae are used as outgroups. Our study confirms the paraphyly of Dryopteris and provides the first strong molecular evidence on the monophyly of Acrophorus, Diacalpe, Dryopsis, Nothoperanema, and Peranema. However, all these monophyletic groups together with the paraphyletic Acrorumohra are suggested to be merged into Dryopteris based on both molecular and morphological evidence. Our analysis identified 13 well-supported monophyletic groups. Each of the 13 clades is additionally supported by morphological synapomophies and is inferred to represent a major evolutionary lineage in Dryopteris. In contrast, monophyly of the four subgenera and 15 out of 19 sections currently recognized in Dryopteris s.s is not supported by plastid data.
The genera, Acrophorus, Acrorumohra, Diacalpe, Dryopsis, Nothoperanema, and Peranema, should all be merged into Dryopteris. Most species of these genera share a short rhizome and catadromic arrangement of frond segments, unlike the sister genus of Dryopteris s.l., Arachniodes, which has anadromic arrangement of frond segments. The non-monophyly of the 19 out of the 21 supraspecific taxa (sections, subgenera) in Dryopteris strongly suggests that the current taxonomy of this genus is in need of revision. The disagreement between the previous taxonomy and molecular results in Dryopteris may be due partly to interspecific hybridization and polyplodization. More morphological studies and molecular data, especially from the nuclear genome, are needed to thoroughly elucidate the evolutionary history of Dryopteris. The 13 well-supported clades identified based on our data represent 13 major evolutionary lineages in Dryopteris that are also supported by morphological synapomophies.
蕨类植物瓶尔小草科（Dryopteridaceae）的铁角蕨属（Dryopteris）是北半球温带森林中最常见和物种最丰富的蕨类植物之一，全世界约有 225-300 种。铁角蕨属的范围一直存在争议，随着时间的推移，各种相关的属被包括或排除在铁角蕨属之外。属下的系统发育在很大程度上仍然不清楚，而且铁角蕨属的大多数超种分类群的位置从未使用分子数据进行过测试。
在这项研究中，使用了四个质体基因座（rbcL 基因、rps4-trnS 间隔区、trnL 内含子、trnL-F 间隔区）的 DNA 序列来重建铁角蕨属的系统发育。我们的分析共采样了 122 个样本，代表了包括 Acrophorus、Acrorumohra、Diacalpe、Dryopsis、Nothoperanema 和 Peranema 在内的扩展铁角蕨属的 100 种。包括铁角蕨属 s.s. 在内的所有四个亚属和 19 个节都被包括在内。以 Dryopteridaceae 的 Arachniodes、Leptorumohra 和 Lithostegia 的一个物种作为外群。我们的研究证实了铁角蕨属的并系性，并首次提供了关于 Acrophorus、Diacalpe、Dryopsis、Nothoperanema 和 Peranema 的单系性的强有力的分子证据。然而，根据分子和形态学证据，所有这些单系群以及并系的 Acrorumohra 都被建议合并到铁角蕨属中。我们的分析确定了 13 个支持度高的单系群。每个分支都有额外的形态学 synapomophies 支持，并被推断为铁角蕨属中的一个主要进化谱系。相比之下，四个亚属和铁角蕨属 s.s. 中的 19 个节目前的单系性不受质体数据的支持。
Acrophorus、Acrorumohra、Diacalpe、Dryopsis、Nothoperanema 和 Peranema 等属都应归入铁角蕨属。这些属的大多数物种都具有短根茎和叶片片段的逆行排列，与铁角蕨属的姊妹属 Arachniodes 不同，后者的叶片片段具有顺行排列。铁角蕨属的 21 个超种分类群（节、亚属）中有 19 个不是单系的，这强烈表明该属的现行分类法需要修订。铁角蕨属的 19 个超种分类群（节、亚属）中 19 个的非单系性与分子结果之间的不一致可能部分归因于种间杂交和多倍化。需要更多的形态学研究和分子数据，特别是来自核基因组的分子数据，以彻底阐明铁角蕨属的进化历史。我们的数据确定的 13 个支持度高的分支代表了铁角蕨属的 13 个主要进化谱系，这些分支也得到了形态学 synapomophies 的支持。
