川蔓藻属系统分类和演化评述

A review on the taxonomy and evolution of Ruppia

川蔓藻属Ruppia为沉水单子叶植物,世界广布,主要为咸水和盐水生境,具有重要的生态价值、环境指示作用以及植物系统学研究意义。长期以来,川蔓藻属内种的数目以及属的系统位置一直存在争议。根据已有研究资料,目前川蔓藻属共有5个种——R.maritima、R.cirrhosa、R.tuberosa、R.megacarpa和R.polycarpa得到多数学者的认可。关于其系统位置,主要有隶属于眼子菜科Potamogetonaceae和独立成川蔓藻科Ruppiaceae两种观点。尽管目前许多被子植物分类系统都承认了川蔓藻科,近年来分子系统学研究显示川蔓藻属与丝粉藻科Cymodoceaceae和波喜荡科Posidoniaceae有近的亲缘关系,但对川蔓藻属和眼子菜属Potamogeton区别特征的比较结果倾向于支持将其放在眼子菜科。本文还结合川蔓藻属及相关类群的化石记录和果实特征对其演化进行了初步探讨,化石属Limnocarpus和Midravalva被认为是川蔓藻属较早的祖先类群,并认为该属植物应该是由淡水祖先逐渐演变成现在的咸水生长植物。最后,提出了在川蔓藻属未来研究中有待进一步解决的问题。

Ruppia is a genus of submerged monocots that exhibits a nearly worldwide distribution and inhabits mainly brackish and saline waters. This genus has important ecological values and is significant for environment monitoring and plant systematic study. Since Linnaeus＇s time, there existed confusion at both specific and family level about Ruppia. The number of taxa within Ruppia, whether there is a single cosmopolitan species or more than one species, has caused much disagreement among taxonomists. At present, five species, R. maritima, R. cirrhosa, R. tuberose, R. megacarpa and R. polycarpa are generally accepted. As to the systematic position of the genus, there are two main opinions： including Ruppia in the family Potamogetonaceae or keeping it in its own family Ruppiaceae. Some systems of plant taxonomy accepted Ruppiaceae, but comparison of diagnostic characters between Potamogeton and Ruppia tended to retain Ruppia within the Potamogetonaceae, although the molecular analyses in recent years show that Ruppia has a close relationship with Cymodoceaceae and Posidoniaceae. In addition, the evolution of Ruppia is discussed based on fossil records and fruit characters of the related fossil taxa. The fossil genera Limnocarpus and Midravalva are regarded as the ancestors of Ruppia and it is suggested that its present brackish habitat developed from a fresh water ancestor. Finally, some questions which should be paid much attention on further study of this genus are discussed.