An evaluation of tribes and generic relationships in Melioideae (Meliaceae) based on nuclear ITS ribosomal DNA

Abstract

Phylogenetic analyses of Melioideae, including representatives of all currently recognized tribes, were carried out using nuclear ITS ribosomal DNA sequence data. The secondary structure models employed for ITS1 and ITS2 allowed optimization of the alignment across Meliaceae genera of both subfamilies, yielding a maximum amount of information without the exclusion of some highly variable sites. This study is the first to assess the current circumscription of Melioideae and its tribes in detail, with data independent of morphology. Maximum parsimony, maximum likelihood and Bayesian analyses of nuclear ITS, in contrast to analyses based on plastid rbcL, confirm monophyly for Aglaieae, Sandoriceae and Melieae, an isolated position for Vavaeeae, the position of Pterorhachis and Quivisianthe in Melioideae, and a close relationship between Turraeeae and Trichilieae. Trichilieae are morphologically and genetically the most complex tribe. Trichilieae cannot be separated from Turraeeae, Vavaeeae and Sandoriceae. Anthocarapa and Pseudocarapa form a clade but exhibit a high number of autapomorphies, which needs further investigation. We propose to keep Naregamia separate from Turraea, and to reconsider the present circumscription of Trichilieae.