The systematics of tribe Millettieae (Leguminosae-Papilionoideae)

Abstract

The tribe Millettieae belongs to the family Leguminosae. As traditionally circumscribed it comprises approximately 45 genera and over 900 species distributed pantropically and in subtropical regions. Previous phylogenetic studies revealed that many genera in the tribe are not monophyletic. The most problematic genus is the massive genera Millettia. Various authors have attempted to clarify generic circumscription since the genus was established in 1834. This thesis attempts to clarify the phylogenetic relationships of doubtfully placed genera of the tribe Millettieae, with the emphasis on the polyphyletic genus Millettia and its closed allies. Forty-five genera placed in the Millettioid s.l. were sampled for phylogeny reconstruction, representing 22 genera putatively part of the Core Millettieae, 17 genera from the Basal millettioid & phaseoloid group (BMP) of the Millettioid s.str. Group, and six genera from the IRLC Clade. Phylogenetic relationships are reconstructed in this study using Maximum Likelihood and Bayesian analysis. Three DNA markers were used in the study, which included published and newly-generated sequence data. In total, there were 361 sequences of the ribosomal nuclear DNA (nrDNA) ITS region; a combined chloroplast (matK+trnL-F) included 306 individuals, and the total evidence analysis (ITS+matK+trnL-F) included 436 individuals. The Maximum Likelihood and Bayesian analyses which produced comparable phylogenies are largely congruent. The total evidence phylogeny supported the monophyly of genera in Millettioid s.str. Group, namely Antheroporum, Apurimacia, Chadsia, Leptoderris, Mundulea, Philenoptera, Piscidia, Platysepalum, Pongamiopsis, Pyranthus, Solori, Sylvichadsia and Tephrosia, while others were not monophyletic and need to be re-evaluated, namely Dahlstedtia, Deguelia, Derris, Fordia, Lonchocarpus, Millettia, Muellera, Ptycholobium and Requienia. Genera with uncertain placement that now more robustly placed are: Antheroporum and Disynstemon in the Basal Millettioid and phaseoloid group (BMP), and Deguelia, Fordia, Leptoderris, Platysepalum and Sylvichadsia in the Core Millettieae. In case of genus Millettia, all sequences were distributed between Group 1 and Group 2 of the Millettioid s.str. Group, groups which correspond with the Canavanine Group and the Non-canavanine Group. Within these groups eleven subgroups were recognized. iii The distribution of canavanine, a Non-Protein Amino Acid Accumulating (NPAAA), is explored by means of a literature review, in the light of the new phylogenetic hypothesis. The investigation found three species without canavanine in the Canavanine Group, and two species with canavanine in the Non-canavanine Group. Consequently, these groups are considered whether to retain old names or proposed possible alternative names. In order to retain the monophyletic Derris, a need for a new combination and a new name for Millettia pachycarpa Benth. was identified. Here Derris lithocarpa (Benth.) Mattapha & Hawkins, com.nov. et nom.nov. is proposed. In relation to this, a new species of Derris from Thailand is newly described as Derris constricta Mattapha & Hawkins, sp.nov. Furthermore, three new species Millettia are also newly described, two species from Thailand namely M. calcicola Mattapha & Hawkins, sp.nov. and M. khaoyaiensis Mattapha & Hawkins, sp.nov. and another species from Vietnam, M. fulva Mattapha, Forest & Hawkins, sp.nov. However, the generic placement for these new species might yet prove to be provisional, since generic limits remain unsatisfactory