Am J Bot. 1997 Jul;84(7):973.
The Rhododendroideae are usually recognized as a subfamily within Ericaceae. This group has been considered primitive (i.e., occupying the ancestral or basal position relative to all other Ericaceae) due to the occurrence of separate petals in several taxa, deciduous corollas, and septicidally dehiscent capsules. Previous molecular studies using rbcL and nr18s sequences have indicated that Rhododendroideae may be paraphyletic and cladistically derived (i.e., the relative position in the geneology of Ericaceae is not basal). The matK sequences of 42 taxa from traditional Rhododendroideae and potentially related clades were obtained via standard gene amplication and double-stranded dideoxy sequencing. Phylogenetic analyses of these sequences using Actinidia chinensis as the outgroup indicate that the Rhododendroideae are paraphyletic. Trees obtained in the analyses indicate an expanded rhododendroid clade that includes four major subclades - empetroid, rhodo, ericoid, and phyllodocoid. The ericoid clade is sister to the phyllodocoid clade and the empetroid clade is sister to the rhodo clade. Relationships within the clades are generally well resolved except within the rhodo clade where matK data indicate that Rhododendron is probably paraphyletic. Daboecia and Calluna are included within the ericoid clade; Erica is paraphyletic. Cassiope lies outside the rhododendroid clade. The relationships indicated by the matK data suggest that sympetalous flowers are likely plesiomorphic within rhododendroids.
杜鹃亚科通常被认为是杜鹃花科的一个亚科。由于几个分类群中存在分离的花瓣、落叶花冠和裂生蒴果，该类群被认为是原始的（即相对于杜鹃花科的所有其他分类群占据祖先或基础位置）。以前使用 rbcL 和 nr18s 序列的分子研究表明，杜鹃亚科可能是并系的，并且在系统发生上是衍生的（即杜鹃花科的相对位置不是基础的）。通过标准基因扩增和双链双脱氧测序获得了来自传统杜鹃亚科和潜在相关分支的 42 个分类群的 matK 序列。使用猕猴桃作为外群对这些序列进行的系统发育分析表明，杜鹃亚科是并系的。分析中得到的树表明，扩展的杜鹃类群包括四个主要的亚群——鹿蹄草状、杜鹃状、石楠状和叶状。石楠状分支与叶状分支是姐妹分支，鹿蹄草状分支与杜鹃状分支是姐妹分支。分支内的关系通常得到很好的解决，除了在杜鹃状分支中，matK 数据表明杜鹃属可能是并系的。茶藨子属和杉叶藻属被包含在石楠状分支中；石楠属是并系的。卡西奥佩亚属位于杜鹃类群之外。matK 数据所表明的关系表明，合瓣花在杜鹃类群中可能是原始的。
