Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, Wisconsin 53706, USA.
Am J Bot. 2012 Apr;99(4):730-50. doi: 10.3732/ajb.1100294. Epub 2012 Mar 20.
Dryopteris is a large, cosmopolitan fern genus ideal for addressing questions about diversification, biogeography, hybridization, and polyploidy, which have historically been understudied in ferns. We constructed a highly resolved, well-supported phylogeny for New World Dryopteris and used it to investigate biogeographic patterns and divergence times.
We analyzed relationships among 97 species of Dryopteris, including taxa from all major biogeographic regions, with analyses based on 5699 aligned nucleotides from seven plastid loci. Phylogenetic analyses used maximum parsimony, maximum likelihood, and Bayesian inference. We conducted divergence time analyses using BEAST and biogeographic analyses using maximum parsimony, maximum likelihood, Bayesian, and S-DIVA approaches. We explored the monophyly of subgenera and sections in the most recent generic classification and of geographic groups of taxa using Templeton tests.
The genus Dryopteris arose ca. 42 million years ago (Ma). Most of the Central and South American species form a well-supported clade which arose 32 Ma, but the remaining New World species are the result of multiple, independent dispersal and vicariance events involving Asia, Europe, and Africa over the last 15 Myr. We identified six long-distance dispersal events and three vicariance events in the immediate ancestry of New World species; reconstructions for another four lineages were ambiguous.
New World Dryopteris are not monophyletic; vicariance has dominated the history of the North American species, while long-distance dispersal prevails in the Central and South American species, a pattern not previously seen in plants.
水龙骨科是一个大型的世界性蕨类植物属，非常适合解决多样性、生物地理学、杂交和多倍体等问题，这些问题在蕨类植物中历史上研究不足。我们构建了一个高度解析、支持良好的新世界水龙骨科系统发育，并利用它来研究生物地理格局和分化时间。
我们分析了包括来自所有主要生物地理区域的分类群在内的 97 种水龙骨科的关系，使用来自七个质体基因座的 5699 个对齐核苷酸进行分析。系统发育分析使用最大简约法、最大似然法和贝叶斯推断法。我们使用 BEAST 进行分化时间分析，使用最大简约法、最大似然法、贝叶斯法和 S-DIVA 方法进行生物地理分析。我们使用 Templeton 检验探索了最近通用分类中亚属和节的单系性以及分类群的地理群。
水龙骨科属约于 4200 万年前（Ma）出现。大多数中美洲和南美洲的物种形成了一个支持良好的分支，该分支出现于 32 Ma 前，但其余的新世界物种是过去 1500 万年中涉及亚洲、欧洲和非洲的多次独立扩散和地理隔离事件的结果。我们在新世界物种的直接祖先中鉴定出了六个远距离扩散事件和三个地理隔离事件；对另外四个谱系的重建结果存在不确定性。
新世界水龙骨科不是单系的；地理隔离在北美物种的历史中占主导地位，而远距离扩散则在中美洲和南美洲的物种中占主导地位，这是植物中以前未见过的模式。
