PHYLOGENETIC-RELATIONSHIPS OF RHODODENDROIDEAE (ERICACEAE)

The Rhododendroideae are usually recognized as a subfamily within Eric aceae. This group has been considered primitive (i.e., occupying the a ncestral or basal position relative to all other Ericaceae) due to the occurrence of separate petals in several taxa, deciduous corollas, an d septicidally dehiscent capsules. Previous molecular studies using rb cL, and nr18s sequences have indicated that Rhododendroideae may be pa raphyletic and cladistically derived (i.e., the relative position in t he geneology of Ericaceae is not basal). The matK sequences of 42, tax a from traditional Rhododendroideae and potentially related clades wer e obtained via standard gene amplication and double-stranded dideoxy s equencing. Phylogenetic analyses of these sequences using Actinidia ch inensis as the outgroup indicate that the Rhododendroideae are paraphy letic. Trees obtained in the analyses indicate an expanded rhododendro id clade that includes four major subclades-empetroid, rhode, ericoid, and phyllodocoid. The ericoid clade is sister to the phyllodocoid cla de and the empetroid clade is sister to the rhode clade. Relationships within the clades are generally well resolved except within the rhode clade where matK data indicate that Rhododendron is probably paraphyl etic. Daboecia and Calluna are included within the ericoid clade; Eric a is paraphyletic. Cassiope lies outside the rhododendroid clade. The relationships indicated by the matK data suggest that sympetalous hewe rs are likely plesiomorphic within rhododendroids.