基于 ITS 序列探讨睡莲属植物的系统发育

对睡莲属Nymphaea L．11个种和外类群中国莲Nelumbo nucifera Gaertn．nrDNA的ITS区(包括ITS-1，5．8SrDNA和ITS-2)进行了序列测定．睡莲属植物的ITS序列总长度为678～711bp，ITS-1和ITS-2序列长度范围为246～275bp和266～275bp．当空位(gap)作缺失处理时，睡莲属植物ITS区全序列排序后的长度为735位点，其中有265个(101个位点在ITS-1区，164个位点在ITS-2区)为系统发育的信息位点．以Nelumbo nucifera Gaertn．为外类群，利用PAUP4．0b4a软件。采用最大简约法分析获得了2个最简约树，其步长为658，一致性指数(CI)和维持性指数(RI)值分别为0．8450和0．8555．利用2个最简约树获取严格一致树，结果表明：热带睡莲植物和耐寒睡莲植物分别聚成一支构成姊妹群，这与基于起源和对生态条件的不同要求、或根据心皮的排列方式而对睡莲属植物进行的传统分类一致．在热带睡莲植物内形成两个亚支，其内部支持率均为100％；耐寒睡莲植物内也形成了两个亚支，内部支持率分别为98％和85％．

Phylogeny Relationship of Nymphaea L.Based on ITS Sequences

The internal transcribed spacer (ITS) regions of nuclear ribosomal DNA from 11 species of Nymphaea L. and one outgroup species of Nelumbo nucifera Gaertn. were sequenced. The regions ranged in length from 678 to 711 bp, with ITS-1 (246-275 bp) slightly shorter than ITS-2 (266-275 bp). Of the 735 aligned sites, 265 sites (101 in ITS-1, 164 in ITS-2) were phylogenetically informative and the number of phylogenetically informative loci was higher in ITS-2 than in ITS-1. Taking Nelumbo nucifera Gaertn. as outgroup, phylogenetic analysis of ITS sequences using PAUP4.0b4a software obtained two most parsimonious trees (Length=658, CI=0.845 0 and RI=0.855 5) when the gaps were treated as missing. The concensus tree indicated that Nymphaea L. could be divided into two main clades. One clade was tropical water lily, the other clade was hardy water lily. And the results of ITS sequences analysis were consistent with that of the traditional division of Nymphaea L. on the basis of the different regions, habits or the division of seedpods. At the same time, the tropical water lily was divided into two subclades with identical bootstrap values of 100% and the hardy water lily was also divided into two subclades with bootstap values of 98% and 85% repectively.