对南北极地衣优势共生藻的初步探究

PRELIMINARY STUDY ON PREPONDERANT PHOTOBIONTS FROM ANTARCTICA AND ARCTIC

对采集自南极乔治王岛和北极新奥尔松地区的32份地衣标本中共生藻rDNA ITS序列进行测定,发现均为Trebouxia jamesii;结合Genbank中来自不同地区地衣中该藻的序列信息,发现T.jamesii的基因型与地衣物种及采集地都没有明确的对应关系。广布于全球范围的T.jamesii作为地衣优势共生藻,存在多种基因型,并且可以被多种地衣共生菌选择;其中优势基因型A在采集自南极洲、欧洲、北美洲和北极地区的地衣中均有发现,而其他基因型则在一定程度上出现地区特有性。本研究为地衣中的藻交换提供了证据,并提出地衣体碎片是实现地衣共生藻长距离传播的载体。

Thirty-two photobiont ITS ribosomal DNA sequences which were applied from the lichen samples collected from the King George Island, Antarctica and Ny-Alesund, Arctic were determinded, and all the photobionts were identi- fied as Trebotaxla jamesii. A phylogenetic analysis was conducted based on the ITS rDNA sequences of photobionts in this study and those retrieved from Genbank, and the result indicated that genotypes of photobionts do not match the species of lichens or their sampling sites. As a dominant photobiont species distributing on a global scale, T. jamesii harbors numerous genotypes and can be found in various lichen species. Among these genotypes, genotype A were found in the Antarctica, Europe, North America and Arcitc, whereas the other genotypes exhibited regional specificity. The present study supplies the evidence in algal switching among lichens, and suggests that the frag- ments of lichen thallus could be the carrier for photobionts＇ long distance spreading.