Biology Department CB#1137, One Brookings Dr, Washington University, St Louis, Missouri 63130, USA.
Evolution. 2010 Jan;64(1):217-31. doi: 10.1111/j.1558-5646.2009.00797.x. Epub 2009 Jul 30.
A central problem in evolutionary biology is identifying factors that promote the evolution of reproductive isolation. Among mosses, biogeographic evidence indicates that the potential for migration is great, suggesting that biological factors other than geographic isolation may be critical for speciation in this group. The moss Physcomitrella patens (Funariaceae) has long been used as a model for interspecies hybridization and has recently emerged as an important model system for comparative genomics. We report genealogical analyses of six loci from several populations of P. patens and related species in the genus Physcomitrium. These results unambiguously indicate that the so-called genus Physcomitrella arose at least three times from distinct ancestors within the genus Physcomitrium. In spite of the evidence for natural hybridization in the Physcomitrella-Physcomitrium complex, genealogical and experimental hybridization data indicate that the taxonomically defined species are reproductively isolated. However, these analyses suggest that Physcomitrium eurystomum was formed from a hybridization event between two early diverging lineages in the complex, and that the ancestral population size of these lineages was much smaller than the current population sizes. We discuss these findings in the context of the inferred mating system in the Physcomitrella-Physcomitrium complex and patterns of speciation and diversification.
进化生物学中的一个核心问题是确定促进生殖隔离进化的因素。在苔藓植物中，生物地理证据表明迁移的潜力很大，这表明对于该类群的物种形成，地理隔离以外的生物因素可能是至关重要的。藓类植物 Physcomitrella patens（金发藓科）长期以来一直被用作种间杂交的模型，并且最近已成为比较基因组学的重要模型系统。我们报告了来自 Physcomitrella patens 及其相关属 Physcomitrium 中的几个种群的六个基因座的系统发育分析。这些结果明确表明，所谓的 Physcomitrella 属至少是由 Physcomitrium 属内的三个不同祖先衍生而来的。尽管在 Physcomitrella-Physcomitrium 复合体中存在自然杂交的证据，但系统发育和实验杂交数据表明，在分类学上定义的物种是生殖隔离的。然而，这些分析表明，Physcomitrium eurystomum 是由复合体中两个早期分化谱系之间的杂交事件形成的，这些谱系的祖先种群规模比当前种群规模要小得多。我们将这些发现与 Physcomitrella-Physcomitrium 复合体中推断的交配系统以及物种形成和多样化的模式联系起来进行讨论。
