MOLECULAR SYSTEMATICS OF RHODODENDRON SUBGENUS TSUTSUSI (RHODOREAE, ERICOIDEAE, ERICACEAE)

Abstract

Rhododendron subgenus Tsutsusi (Rhodoreae, Ericoideae, Ericaceae), commonly known as evergreen azaleas, includes approximately 117 deciduous and evergreen species from Japan, China and northeastern Asia. Subgenus Tsutsusi has been divided into two sections, Brachycalyx and Tsutsusi, based on characteristics of the leaves, young twigs and corolla. We obtained molecular data from three chloroplast (matK, ndhF and trnS-trnG) and two nuclear (nrITS and the third intron of rpb2) regions for 30 species of Rhododendron subgenus Tsutsusi and five species of Menziesia. Parsimony, Bayesian and likelihood analyses based on total evidence were used to assess the monophyly of the sections within Rhododendron subgenus Tsutsusi and relationships among the species sampled. In particular, the placement of the problematic Rhododendron tashiroi was addressed. Results support Rhododendron tashiroi as a member of the Rhododendron section Brachycalyx clade. Molecular evidence also supports a clade within Rhododendron section Tsutsusi containing R. indicum, R. tsusiophyllum, R. tschonoskii and R. serpyllifolium, species which were not previously considered closely related.