Groups of Dalbergia present in Madagascar:
Two main broad groups of species can be distinguished on the basis of a preliminary, unpublished phylogenetic study, likely representing 2 separate migration events to Madagascar: Supergroup 1: plants with relatively large flowers and relatively small racemose or paniculate inflorescences; and Supergroup 2: plants generally with small flowers in large well-branched paniculate cymes. These supergroups can be further divided into 3 and 7 subgroups respectively, that each possess a suite of differential characters and coherent biogeography.
In addition at least two species appear to belong outside these groups (and separate from each other), and include the liana D. bracteolata the only species in Madagascar that also occurs elsewhere, and D. xerophila a shrub or small tree from the south-west, and characterised by typical xeromorphic features including the development of brachyblasts.
Taxonomy
Recently it has become clear that the existing taxonomy of the genus requires revision and the delimitation of certain species is problematic. Collaborative efforts are now underway to address these issues, and will be incorporated here as they progress. A working list of potential new species, and their associated specimens is provided here. It is envisaged that the total number of species recognized in Dalbergia for Madagascar may be close to 100.
Exploitation of timber and protection of data
Numerous species of Dalbergia are exploited for their timber and are known in Madagascar as "Bois de rose" (Rosewood) or "Palissandre" (Palisander). Many of them are threatened through over-exploitation and illegal logging. In the treatment presented here in the Madagascar Catalogue, data are withheld (in particular geo-coordinates and detailed locality information) for species that may develop into sufficiently large trees to be potential sources of valuable wood, which are under significant pressure in Madagascar from illegal, unsustainable exploitation (Mason et al., 2016). A list of taxa, including as yet unpublished species, currently considered to capable of developing into large trees that produce commercially valuable timber is provided here: Malagasy Dalbergia large tree species list.
Reference
Mason J., M. Parker, L. Vary, P.P. Lowry II, S. Hassold & G. Ruta (2016). Malagasy precious hardwoods: Scientific and technical assessment to meet CITES objectives. Report submitted by the World Resources Institute and the World Bank, Washington. [https://www.scribd.com/document/318123493/WRI-WB-Malagasy-Precious-Woods-Assessment-1-pdf]
Hybridization is believed to occur between closely related species of Dalbergia in Madagascar, based on observations in the field and evidence from molecular species. We believe that this accounts, at least partially, for the difficulty experienced in the past with respect to species delimitation and specimen determination.