Phylogeny and systematics of African Melastomateae (Melastomataceae)
Résumé
Melastomateae are the most species-rich (185 spp./13 gen.) and morphologically diverse tribe within the African
Melastomataceae. In this study we present the first in-depth phylogenetic analysis of African Melastomateae using sequences
generated from one nuclear (nrITS) and two plastid spacers (accD-psaI, psbK-psbL) sampling 183 accessions representing 75
African, 10 Madagascan and 7 Asian species and a broad outgroup sampling. We infer phylogenetic relationships using maximum
likelihood, maximum parsimony and Bayesian approaches and propose a revised generic classification of African Melastomateae
based on our molecular trees in combination with a careful reassessment of morphological variation. Our phylogenetic analyses
support the monophyly of Old World Melastomateae except Dinophora which clearly falls outside Melastomateae. Asian and
Madagascan endemic genera of Melastomateae are nested among the African genera. Of the African genera only two monophyletic groups, Dichaetanthera and Tristemma, are recovered in addition to the monospecific Pseudosbeckia lineage, while
Antherotoma, Dissotis and Heterotis as currently circumscribed are polyphyletic. However, the subgenera and sections of these
genera are mostly recovered as morphologically distinct and molecularly well-supported clades. Isomorphism versus dimorphism
of the stamens is found to be an unreliable character when delimiting genera in Melastomateae. We propose the reinstatement
of Argyrella and Dupineta, a new status at generic rank for Dissotis subg. Dissotidendron, a broadened circumscription of
Guyonia (to include the species previously placed in Heterotis sect. Cyclostemma), and description of a new, monospecific genus
Anaheterotis for the Heterotis pobeguinii lineage. Heterotis is maintained at generic rank but with a narrower circumscription
in comparison to earlier treatments. We accommodate the rare Osbeckia porteresii lineage from Mt. Nimba (Guinea) within
an expanded Melastomastrum. To complete our generic realignment, a total of 42 new combinations are effected at the species
level and below, and a key is provided for the 12 genera presently recognised in African Melastomateae. Denser taxonomic
sampling and sequencing of more loci will be needed to resolve relationships within the large clade of Dissotis s.str. and allies
(including Antherotoma as well as three West African species erroneously placed in the otherwise Asian Osbeckia).