基于ITS序列探讨杜鹃花属马银花组的系统发育

Phylogenetic relationships of Rhododendron section Azaleastrum (Ericaceae) based on ITS sequences

以杜鹃花属叶状苞亚属Rhododendronsubg .Therorhodion (Maxim .)Gray的叶状苞杜鹃R .re dowskianumMaxim .为外类群 ,使用PAUP4.0b8软件对马银花亚属subg .AzaleastrumPlanch .的马银花组sect.Azaleastrum (Planch.)Maxim .7种 1变种和长蕊杜鹃组sect.ChoniastrumPlanch .2种及 2个相关的单型亚属 (异蕊杜鹃亚属subg .MumeazaleaMaxim .和纯白杜鹃亚属subg.Candidastrum (Sleumer)Philip .&Philip.)进行了系统发育分析。采用最大简约法分析获得 6个最简约树 ,步长为 6 0 ,一致性指数 (CI)和维持性指数 (RI)值分别为 0 .91 7和 0 .898,利用 6个最简约树获取严格一致树。用最大似然法获得的系统树与严格一致树完全相同 ,只是支持率略有不同。结果表明纯白杜鹃亚属位于系统树的基部 ;马银花亚属不是一个单系类群 ,但马银花组和长蕊杜鹃组分别构成单系 ,支持率分别为 81 %和 1 0 0 % ;在马银花组内形成两个分支 ,内部支持率分别为 93 %和 6 2 %。

The subgenus Azaleastrum Planch. of Rhododendron L. (Ericaceae) was traditionally divided into two sections, i. e. sect. Azaleastrum ( Planch.) Maxim. and sect. Choniastrum Planch. The internal transcribed spacer (ITS) regions of nuclear ribosomal DNA from seven species and one variety of subg. Azaleastrum were sequenced. The ITS sequences of these taxa, together with those of two species of sect. Choniastrum and two related monotypic subgenera, subg. Mumeazalea Maxim. and subg. Candidastrum (Sleumer) Philip. & Philip., were analyzed to reconstruct the phylogeny of the sect. Azaleastrum using PAUP4.0b8, with R. redowskianum Maxim. of subg. Therorhodion (Maxim.) Gray as outgroup. Six most parsimonious trees with a length = 60, a CI = 0.917, and an RI = 0.898 were obtained by the maximum parsimony analysis when the gaps were treated as missing. The topology of the strict consensus tree was identical with that of the maximum likelihood analysis with slightly different bootstrap values. Subg. Candidastrum was nested in the basal position. Subg. Azaleastrum was not monophyletic, but both sect. Azaleastrum and sect. Choniastrum were monophyletic groups with bootstrap values of 81% and 100% respectively. Sect. Azaleastrum was divided into two clades with bootstrap values of 93% and 62% respectively. Subg. Mumeazalea was resolved as sister to sect. Azaleastrum.