一株具有新特征的轮藻及其分类地位探讨

A study of the new characteristic charophyte and the classification status

摘要:

本研究基于在四川雅安采集到的一株特殊轮藻，通过形态学观察，显示其具有茎与小枝无皮层，小枝分叉，冠细胞两层等丽藻族特征。但在茎节小枝基部具有新特征——乳突状托叶，目前尚未有丽藻具有托叶的相关报道。在野外采集的新特征轮藻植株、采集回实验室稳定培养一段时间的植株以及采集到的轮藻合子萌发的后代植株均能观察到上述特征，说明其特征是稳定遗传的。进一步使用18S rDNA与rbcL基因联合分子系统发育分析，结果显示新特征轮藻与丽藻属其它种类聚在一起且成为单独的一支。结合形态学与分子系统发育学结果，说明了新特征轮藻应划分到丽藻属内，也表明托叶不再仅仅是轮藻族独有的特征，丽藻族中也应增加托叶这一特征；新特征轮藻的发现对丽藻属是一个重要的补充，并为现有的轮藻分类系统的完善与修订提供了重要材料。

Abstract:

This study was focused on a special charophyte collected from Ya'an, Sichuan. Morphological observation showed that it had two-layer coronal, divided branchlets and no cortex. These were the features of Nitelleae. But there was another feature which hadn’t been reported in Nitelleae, papillary stipulodes, at the base of node and beneath the branchlets. The identical stipulodes were observed no matter in the fresh collected samples or in the laboratory cultured specimens or in the seedlings coming from the germinated oospores in the laboratory. Long time observation indicated that the stipulodes feature was stably inherited in this special charophyte. Further molecular phylogenetic analyses, which combined the 18s rDNA gene with the rbcL gene, demonstrated that new feature charophyte clustered with other species of Nitella as a single clade. Combining the morphological observation with the molecular analyses illustrated the new feature charophyte belonged to Nitella. Our research demonstrated that not only the Chareae but also the Nitelleae had stipulode. And the new feature charophyte was an important supplement to Nitella. New feature charophyte provided an evidence for the revision of the classification system of charophytes.