Systematic studies in the Boea group

Abstract

Since it was first published, many additional species have been ascribed to the genus Boea Comm. ex Lam. As the genus grew in size, it also grew in morphological diversity until it was recircumscribed and became the source of a number of new segregate genera. Today, the Boea group (i.e. Boea, the segregate genera and other close relatives) comprises over 200 species in some 15 genera, found from China to Australia and throughout Malesia from Sumatra to the Solomon Islands. Previous molecular studies suggested a much more complex structure to the clade than previously thought. Here the most up to date phylogeny, covering all the genera known to belong to the Boea group, is presented. Parsimony and Bayesian Inference were the chosen approaches to the phylogenetic analysis of nine matrices generated using DNA data from 277 accessions. The markers used were the nuclear ITS and the chloroplast regions trnL-trnF (intron and spacer) and ndhF-rpl32-trnLUAG. The results show important discrepancies between the current taxonomy of the group and the clades delineated by the phylogeny. In an attempt to establish a natural classification of Boea and its allies, taxonomic and nomenclatural work was carried out on most of the genera found to be non-monophyletic. Boea Comm. ex Lam. is divided into two genera. The recircumscribed Boea is restricted to the group of taxa found in New Guinea, Solomon Islands and Australia. The genus is fully revised and contains 11 species, including the newly described Boea morobensis C.Puglisi. The Southeast Asian group of species formerly attributed to Boea, centred in Thailand, is given the resurrected name Dorcoceras Bunge. To the four species traditionally known to belong to this group, three new ones are added. These are Dorcoceras brunneum C.Puglisi, D. glabrum C.Puglisi and D. petiolatum C.Puglisi. Damrongia is deeply transformed with the synonymisation of D. cyanantha Triboun in D. trisepala (Barnett) D.J.Middleton & A.Weber, and the inclusion of Boea clarkeana Hemsl. and the three Asian species of Streptocarpus Lindl., S. orientalis Craib, S. burmanicus Craib and S. sumatranus B.L.Burtt. As a result of the phylogenetic study, a new genus, Middletonia C.Puglisi, is segregated from Paraboea. Middletonia consists of five species, including the newly described Middletonia glebosa C.Puglisi, and has its centre of distribution in Thailand. Finally, Paraboea (C.B.Clarke) Ridl. is recircumscribed with the inclusion of the genera Trisepalum C.B.Clarke and Phylloboea Benth. In order to limit the number of new combinations needed and maintain clarity, the name Paraboea was conserved against both Phylloboea and Trisepalum. In addition to the 15 new combinations in Paraboea, a new species from the Philippines, P. zamboangana C.Puglisi, is described.