The Dalbergioid Legumes (Leguminosae: Papilionoideae)

Systematics, taxonomy, floristics, biogeography and uses of Dalbergioid legume genera.

Pterocarpus rohrii (Image: Gwilym Lewis)

The “Dalbergioid legumes” constitute a recently recognized monophyletic group of 49 papilionoid legume genera which previously belonged to four different tribes (Adesmieae, Aeschynomeneae, Dalbergieae and Desmodieae subtribe Bryinae). The formal recognition of this group represents one of the largest rearrangements of the papilionoid legumes in recent time. The phylogenetic resolution among the genera, and biogeographic understanding of this largely pantropical group, is lacking but extremely interesting, and the taxonomic knowledge of each constituent genus is very variable. As several of the Dalbergioid genera contain many of the worldʼs most commercially important timber species and ornamental street trees, plus edible and medicinal plants (e.g. Brya ebenus DC. = West Indian ebony, Dalbergia nigra (Vell.) Allemao ex. Benth. = rose wood, Tipuana tipu (Benth.) Kuntze = tipu, Pterocarpus tinctorius Welw. = sangre de draco and Arachis hypogaea L. = peanut), there is, from a biodiversity, conservation, commercial uses and biogeographic standpoint, a need for a global multidisciplinary project to study this plant group.

The project addresses the following questions: (1) What is the phylogenetic relationship among the constituent genera? (2) Which biogeographic distribution patterns do the Dalbergioid legumes follow and what are the ages of the clades which constitute them? (3) What are the relationships among the species of the constituent genera and how do these compare with their current taxonomic frameworks? and (4) What do these patterns tell us about the known uses of the species?

The project aims to answer the questions using a variety of approaches, including field work (to gather fresh material for analysis, ecological data and images), molecular sequencing, palynological and wood anatomical methods, analyses of chemical compounds, flower and fruit micromorphological surveys (using SEM and TEM), and herbarium collections-based taxonomic methods. Outputs from the project have included, and will continue to include, comparative science papers in high-impact journals, taxonomic monographs of selected genera, and treatments in local floras (these usually including species conservation assessments).

Key publications 2006-2011

• Lozano, P. & Klitgård, B.B. (2006). The genus Machaerium (Leguminosae: Dalbergieae) in Ecuador. Brittonia 58(2): 124–150.
• Saslis-Lagoudakis, C.H., Chase, M.W., Robinson, D.N., Russell, S.J. & Klitgård, B.B. (2008). Phylogenetics of Neotropical Platymiscium (Leguminosae: Dalbergieae): systematics, divergence times, and biogeography inferred from nuclear ribosomal and plastid DNA sequence data. American Journal of Botany 95 (10): 1270–1286.
• Pirie, M.D., Klitgård, B.B. & Pennington, R.T. (2009). Revision and biogeography of Centrolobium (Leguminosae, Papilionoideae, Dalbergieae). Systematic Botany 34(2): 345–359.
• Gasson, P., Miller, R., Stekel, D., Whinder, F. & Zieminska, K. (2010). Wood identification of Dalbergia nigra (CITES Appendix I) using quantitative wood anatomy, principal components analysis and naïve Bayes classification. Annals of Botany 105: 45-56.
• Saslis-Lagoudakis, C.H., Klitgård, B.B., Forest, F., Francis, L., Savolainen, V., Williamson, E.M. & Hawkins, J.A. (2011). The use of phylogeny to interpret cross-cultural patterns in plant use and guide medicinal plant discovery: an example from Pterocarpus (Leguminosae). PLoS ONE 6(7): e22275 (open access).