Origin and evolution of the northern hemisphere disjunction in the moss genus Homalothecium (Brachytheciaceae)
Origin and evolution of the northern hemisphere disjunction in the moss genus Homalothecium (Brachytheciaceae)
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DOI：
10.3732/ajb.2007407
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发表时间：
2008-06-01
影响因子：
3
通讯作者：
Vanderpoorten, Alain
中科院分区：
文献类型：
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作者：
Huttunen, Sanna;Hedenas, Lars;Vanderpoorten, Alain
竞争的假设，依赖于一个垫脚石通过北大西洋或白令陆桥，或最近的跨洋传播，已被提出来解释地中海植物群在欧洲南部和北美西部的间断分布。这些假设进行了测试与分子测年使用的藓类属Homalothecium的ITS，atpB-rbcL，和rpl 16序列数据的基础上的发育。在古北界西部（欧洲、中亚和北非）和北美的两个主要谱系的单系性与古代的隔离假说是一致的。Madeiran H. sericeum加入支持Macaronesian地方H. mandonii。记录在陆地植物的分子进化的绝对速率的范围内被用作概率校准之前，由贝叶斯推理实现一个松弛的时钟模型，以获得感兴趣的节点的年龄。对美洲和西部古北界同囊藓属分支分歧的年龄估计（5.7Ma，IC 3.52-8.26）和H. mandonii（2.52 Myr IC 0.86-8.25）与古代分隔假说不一致。年龄估计表明，物种分布的结果，从罕见的情况下，分散和随后的同域多样化。校准的同源性表明，Homalothecium经历了快速的辐射在过去的4万年，这是一致的兄弟物种之间的形态分歧的低水平。
Competing hypotheses that rely either on a stepping-stone dispersal via the North Atlantic or the Bering land bridges, or more recent transoceanic dispersal, have been proposed to explain the disjunct distribution of Mediterranean flora in southern Europe and western North America. These hypotheses were tested with molecular dating using a phylogeny of the moss genus Homalothecium based on ITS, atpB-rbcL, and rpl16 sequence data. The monophyly of two main lineages in Western Palearctic (Europe, central Asia and north Africa) and North America is consistent with the ancient vicariance hypothesis. The monophyly of Madeiran H. sericeum accessions supports the recognition of the Macaronesian endemic H. mandonii. A range of absolute rates of molecular evolution documented in land plants was used as probabilistic calibration prior by a Bayesian inference implementing a relaxed-clock model to derive ages for the nodes of interest. Our age estimates for the divergence of the American and Western Palearctic Homalothecium clade (5.7 Ma, IC 3.52-8.26) and the origin of H. mandonii (2.52 Myr IC 0.86-8.25) are not compatible with the ancient vicariance hypothesis. Age estimates suggests that species distributions result from rare instances of dispersal and subsequent sympatric diversification. The calibrated phylogeny indicates that Homalothecium has undergone a fast radiation during the last 4 Myr, which is consistent with the low levels of morphological divergence among sibling species.