世界光萼苔属的分类和地理分布

Porella L., a large well defined genus of liverwiorts with a worldwide distribution, contains 85 currently accepted species. Several species of the genus has been classified as critically endangered or even extinct. Owing to its wide phenotypic plasticity and morphologic variation, it is considered to be one of groups taxonomically difficult in liverworts. The preliminary molecular phylogeny also indicates that there is much debate about classification of the genus, especially infrageneric and specific taxonomy. China has the richest species of Porella, accounting for about about 50% of the total species number of the world，and the taxa endemic to China accounting for one third of Chinese species. It is a genus with richest endemics and concerned greatly. The group is the important one for the study on the origin of bryophytes. Unfortunately, the taxonomy of the genus in China has not been reviewed and the exact number of species is still unknown. By the combined methods of morphological taxonomy, molecular systematics and geography distribution we will carry out the first worldwide revision of the genus, establish a new classification system, reveal the exact species diversity of China and the world, and expore the origin place and time by intensive field collections, detailed observations on key characters from fresh samples, cryo–SEM observations on sporophytes, and sequences of nucleus and chloroplast genes.

光萼苔属是苔类植物中界定很清晰的一个世界分布的大属，目前有85个种，有多个种被评定为极度濒危甚至可能已经灭绝。由于极其丰富的表现可塑性和形态变化，该属被认为是苔类植物中分类最困难的类群，初步的分子系统学研究也表明现有的分类系统和种间分类问题颇多。我国是光萼苔属种类最丰富的国家，占世界种的总数的近一半，其中我国特有种就占到三分之一，是我国苔类植物中特有成分最丰富的类群，备受关注，被认为是研究苔献植物起源的重要类群，但遗憾的是该属在我国还没有作过分类的修订，确切的物种数目仍然不明。本研究以世界范围的光萼苔属植物为对象,拟运用形态分类、分子系统学、化石和地理分布相结合的方法, 通过深入的野外采集，新鲜材料关键特征的观察、孢子体特征的冰冻扫描电镜观察以及核和叶绿体相关基因测序, 首次作世界范围的分类修订，建立新的分类系统，揭示我国和世界光萼苔属确切的物种多样性和地理分布,并探讨其起源地和时间。

由于极其丰富的表现可塑性和形态变化，光萼苔属是由被认为是苔类植物中分类最困难的类群。我国是光萼苔属种类最丰富的国家，占世界种的总数的近一半。这个属是我国苔类植物中特有成分最丰富的类群，备受关注，但遗憾的是该属在我国还没有作过分类的修订，确切的物种数目仍然不明。本研究通过对亚洲，大洋洲和非洲的艰苦野外采集、新鲜材料和腊叶标本关键特征的观察、扫描电镜观察以及核和叶绿体相关基因（ITS, rbcL, trnL-trnF等）测序，重点研究了该属的分类和分布，获得如下重要结果：1) 光萼苔属全世界有86种，我国有36种；2）6个变种需要恢复到种的地位；3）8个分类单位在我国的记录是错误的，应该排除；4）在我国广泛分布的光萼苔（Porella pinnata L.）是前人错误的鉴定，这个种不在亚洲分布；5）2个中国特有的分类单位（Porella densifolia var. pilosa S.Hatt. et K.C.Chang，Porella sichuanensis S.Hatt. et K.C.Chang）确认是新的异名。这些结果对我国生物多样性的保护和利用有重要的价值。