睡莲科的系统发育:核糖体DNA ITS区序列证据

以金鱼藻Ceratophyllum demersum为外类群,使用PAUP4.0b4A软件对睡莲科Nymphaeaceae植物7属11个代表种的ITS区序列进行了系统发育分析。采用最大简约法分析获得了3个最简约树,步长为1125,一致性指数(CI)和维持性指数(RI)值分别为0.7618和0.7214。利用3个最简约树获取严格一致树。结果表明:(1)莲属Nelumbo位于系统树的基部,自展支持率为100%,可从睡莲科中独立出来成立莲科Nelumbonaceae和莲目Nelumbonales;(2)萍蓬草属Nuphar是一单系类群,位于分支Ⅱ的基部,并和睡莲科其他属(不包括莲属)植物聚在一起构成姐妹群,故萍蓬草属仍应置于睡莲科中;(3)水盾草属Cabomba和莼菜属Brasenia聚成一小支并构成姐妹群,自展支持率为99%,说明这两属之间亲缘关系较近;(4)睡莲属和芡实属Euryale、王莲属Victoria聚成一小支并构成姐妹群,自展支持率为94%,说明三者亲缘关系较近,仍应置于睡莲科中。

Phylogeny of the Nymphaeaceae inferred from ITS sequences

The Nymphaeaceae are one of the most important taxa for understanding the origin and evolution of primitive angiosperms due to its basal position in the cladograms of the angiosperms recently given based both on several gene sequences and on morphological characters, but phylogenetic relationships within the family have not as yet been resolved. The sequences of nrDNA ITS region of 11 species representing seven genera of the Nymphaeaceae and one outgroup, Ceratophyllum demersum, were used to reconstruct the phylogeny of the family using PAUP4.0b4A. Three most parsimonious trees (Length=1125, CI=0.7618 and RI=0.7214) were obtained. In the consensus tree: (1) Nelumbo was basal to the other genera with a bootstrap value of 100% and occupied an isolated position, so it could be separated from the Nymphaeaceae and placed in its own family, Nelumbonaceae, and its own order, Nelumbonales; (2) Nuphar was monophyletic, nested in the basal position of clade II and was strongly supported to be the sister group of the other genera (excluding Nelumbo) of the Nymphaeaceae, suggesting that its traditional inclusion in the Nymphaeaceae should be maintained; (3) Cabomba and Brasenia were sister group and formed a subclade with a bootstrap value of 99%, indicating their close affinity; (4) Nymphaea was strongly supported to be the sister group of a subclade comprising Euryale and Victoria with a bootstrap value of 94%, indicating that they should be placed in the Nymphaeaceae.