The Historical Role of Africa in the Biogeography of the Detarieae (Leguminosae)
Kew is investigating the processes that lead to the current distribution of the tropical forest and woodland legumes of the tribe Detarieae.
The most widely accepted explanation for the current cosmopolitan distribution of the Leguminosae invokes an early Tertiary origin along the Tethys Sea margin. From the mid-Tertiary it was hypothesised that legumes dispersed in a southerly direction from the northern Tethyan (Eurasian) coast into Africa, using recently appeared islands around Turkey and western Asia. This assertion, however, is not congruent with the fossil record for the legumes of tribe Detarieae which have a pantropical distribution but are most diverse in African. The fossil record for Detarieae is much older in Africa than Eurasia which suggests that dispersal would have been south to north, in fact in the opposite direction. Within Detarieae, generic distributions are usually restricted to one of the three main tropical areas and nearly two-thirds of all Detarieae genera are confined to the Afromadagascan region. However, all those genera that do occur in more than one region have part of their extant diversity in Africa. There are eight such genera. Copaifera, Crudia and Cynometra are pantropical as currently circumscribed. Afzelia, Intsia and Sindora occur in Africa and SE Asia whilst Guibourtia and Hymenaea have amphi-Atlantic distributions. This project, started in 2011, will use taxonomic accounts in conjunction with molecular systematics to test generic limits and resolve species relationships. Time-calibrated phylogenetic reconstructions will offer the possibility of addressing questions concerning the processes that have lead to current distribution and diversity in these genera, and the research will focus in particular on the historical role that Africa played in those processes.
Project Partners and Collaborators
University of Montreal, Canada
National Herbarium of the Netherlands,Wageningen University Branch
Chicago Botanic Garden, USA