Phylogenetic Analysis of the Wintergreen Group (Ericaceae) based on Six Genic Regions

Previous phylogenetic studies based on DNA sequence data from the genic regions ndhF, matK, atpB-rbeL (cpDNA) and ITS 2 (nrDNA) strongly support the monophyly of the wintergreen group (Ericaceae: Gaultherieae: Diplycosia, Gaultheria, Tepuia) and have assessed the relationships of its major clades. Other studies that include additional genic regions have been limited to two clades corresponding to various sections or series within Gaultheria. Here we expand both the number of species (from 42 to 104) and genic regions (chloroplast mat K, ndhF, rpl16, trnL-trnF, trnS-trnG, and the complete ITS region) to further assess phylogenetic relationships in the wintergreen group. With the additional data we detected several areas of incongruence between the trees from the nuclear and combined chloroplast analyses, including a topologically deep conflict involving G. procumbens. Such incongruence likely originated from reticulation events, long considered to have influenced the evolution of various lineages in Gaultheria. We also detected a duplication, possibly nuclear-encoded, of the matK region in one of the Australian/New Zealand lineages. A combined six-gene analysis, in which taxa involved in the conflicting topologies were excluded, yielded higher support values for several early-diverging clades. The monophyly of both Diplycosia and Tepuia is corroborated, as is the successive nesting of Tepuia, G. section Hispidulae (both placements of which have newfound strong support), G. ser. Gymnobotrys, and Diplycosia. Whereas several sections or series with more than one species in the most recent classification of Gaultheria are supported as circumscribed (i.e. G. section Amblyandra and series Hispidulae, Myrtilloideae, and Trichophyllae), others comprise species from two to several different clades.