基于系统发育重建揭示绢藓属植物洲际间断分布格局的成因

Intercontinental disjunct distribution patterns and causes have being a reserch focus in the field of evolutionary biology, which also is one of the core issues of adaptive evolution. Bryophytes, as a group of early land plants,is considered the most privitive terrestial higher plants, which play an important role in the investigation the origin and evolution of terrestrial plants. Entodon, best represented in East Asia, tropic America and Africa with a unique intercontinental disjunct distribution pattern, is an ideal representative group to explore the causes of the intercontinental disjunct distribution pattern. The molecular phylogenetic relationship of Entodon, however, has been scarcely studied. In present study, we use multiple gene sequences, including nuclear and organelle genomes, to build the phylogenetic relationship of Entodon; Combined with non-molecular evidences, such as micro-morphology, especially the morphogenesis of peristome structure, we also expect to explore the evolutional trend of peristome characters between the main lineages, and to verify the rationality of classification system established mainly based on morphological characters, and to reconstruct the phylogenetic relationship, and also to revise some taxa with difficulty to identify, and then with the fossil evidence and the derivation of the molecular clock, we expect to infer the origin, spread and the divergence time between the representative groups, and to further elucidate the causes of this unique intercontinental disjunct distribution pattern, which will pave a way for further study of the reponse of bryophytes to the global climate change.

生物类群在洲际间断分布的式样及成因一直是进化生物学的研究热点，同时，对间断分布格局成因的解析也是适应性进化的核心课题之一。苔藓植物是最早登陆的，也是最原始、最简单的植物类群，在探讨陆生植物起源与演化方面具有不可替代的地位。绢藓属植物主要分布于东亚、热带美洲和非洲，呈独特的洲际间断分布格局，是探索生物间断分布格局成因的理想类群。然而，绢藓属的分子系统发育关系一直缺乏研究。本研究采用多基因序列（细胞核和细胞器基因组）构建绢藓属植物的系统发育关系，结合微观形态、特别是蒴齿形态发生等非分子证据，探讨主要谱系间蒴齿形态特征的演化趋势，检验主要基于形态学所建立的绢藓属分类系统的合理性，重建绢藓属植物的系统发育，并对疑难种类进行订正；进而，结合化石证据和分子钟推导，推测代表类群的起源地点、扩散路径及类群间的分歧时间，从而阐明洲际间断地理分布格局的成因，为将来研究苔藓植物对全球气候变化的响应奠定基础。

绢藓属植物主要分布于东亚、热带美洲和非洲，呈独特的洲际间断分布格局，是探索生物间断分布格局成因的理想类群。本项研究通过大量的国内外模式标本的借阅、交换以及多次野外标本的采集，并对收集到的标本进行形态学的检视和测量。同时，采用了5个DNA片段，包括2个核基因片段（ITS1和ITS2）和3个叶绿体基因片段（trnL intron，trnL-F和 trnG intron）对绢藓属的系统发育关系和生物地理学进行了研究。研究结果如下：（1）确定了绢藓属植物有112种；（2）重新评估了绢藓属的分类依据；（3）将单种属Sakuraia归到绢藓属；（4）分子系统发育的结果支持将绢藓属分为两个亚属，且与形态学研究结果具有很好的一致性；（5）结合本项研究野外采集工作，进行了崇明岛苔藓植物区系和生态学调查，初步探讨了立碗藓植物种群遗传结构对土壤盐度的适应性。因此，本项研究初步解决了绢藓属系统学上长期存在的属下分类之争的难题，揭示了重要类群间的系统发育关系和性状进化，为洲际间断分布格局历史成因假说提供了新的分子证据，对于更好地理解绢藓属植物原始类群的起源、扩散和演化有着重要意义。