The legumes (family Leguminosae) are the third largest family of flowering plants, with about 19,400 species. Legumes provide food crops, timber, fodder and shade, and fertilise poor soils by nitrogen fixation in their roots.
Legume trees dominate many of the world's most species rich tropical forest ecosystems, but many require basic taxonomic study in order to catalogue their species. For this reason, taxonomic monographs of these genera are a key focus of our research. (See Monographs below.)
We are estimating phylogenies in some of these genera as part of our work in Environmental Change and Biogeography, with particular emphasis on developing a phylogeny for the neotropical genus Inga.
Broad-scale evolutionary relationships within the legumes have also been poorly understood, meaning that the true relationships of economically important, evolutionarily derived groups such as peas, beans, soya and lupins, remain obscure. We are contributing molecular systematic data to global efforts to elucidate legume phylogeny (See generic relationships, below). Our final research area is in legume flower evolution.
Monographs
Taxonomic monographs enable accurate identification of all species and summarise information on their uses, distribution and biology.
The Garden has provided monographs of Geoffroea, Cyclolobium, Andira, Plathymenia, Cenostigma and Barnebydendron. Current work focuses on Berlinia (Caesalpinioideae), Lathyrus and Dussia (Papilionoideae).
Berlinia wood is commercially logged in parts of its range although difficulties in distinguishing species, often compounded by several species being known by the same vernacular name, (e.g. Ebiara), can be an obstacle to assessing the extent of logging of a given species. Commercial forestry is just one of several factors that threaten the conservation of the biodiversity of Berlinia. Others include mining activities, land clearance for agriculture and pressure of human population. Half of the known species of Berlinia qualify for a category of threat as defined by the International Union for the Conservation of Nature. A monograph of Berlinia is being prepared for publication. It will include keys, distribution maps, detailed descriptions, species conservation assessments and present the results of a phylogenetic study which investigated inter- and intra-generic relationships and explored the historical biogeography of the genus.
Lathyrus (the ‘sweet peas'), is the largest genus in tribe Fabeae, the group that contains the true peas (Pisum), lentils (Lens) and vetches (Vicia). Collaborations between RBGE and the University of Tokyo have investigated the molecular phylogenetics and biogeography of Lathyrus. This ongoing study confirms the close relationship between Lathyrus and Pisum, and suggests a Eurasian origin for the South American American lineages. A monograph of the mainly S. American section Notolathyrus is being prepared for publication.
Recent publications
Mackinder, B.A. & Xander M. van der Burgt (2009). Berlinia korupensis (Leguminosae – Caesalpinioideae), a new tree species from Cameroon. Kew Bull. 64(1): 129-134.
Warwick, M. & Lewis, G.P. (2009). A revision of Cenostigma (Leguminosae - Caesalpinioideae). Kew Bull. 64: 135-146.
Warwick, M. & Lewis, G.P. & de Lima, H.C. (2008). A reappraisal of Barnebydendron (Leguminosae – Caesalpinioideae). Kew Bull. 63: 143-149.
Mackinder, B.A. & Harris, D.J. (2006). A synopsis of the genus Berlinia (Leguminosae – Caesalpinioideae). Edinburgh Journal of Botany 63(2-3): 161-182.
Pennington, R.T. (2003). A monograph of Andira (Leguminosae-Papilionoideae). Systematic Botany Monographs. 64: 1-145.
Generic relationships
We have used DNA sequence data to reconstruct phylogeny of basal papilionoid genera. Our sampling of these taxa was thorough, because many have been collected during RBGE's extensive neotropical fieldwork programme. The Garden's collections and information are part of a much wider dataset for the entire legume family produced by several collaborators internationally. The new molecular phylogenies have allowed a re-evaluation of how features such as legume flowers have changed over evolutionary time.
Recent publications
Cronk, Q.C.B., Ojeda, I. & Pennington, R.T. (2005). Legume comparative genomics: progress in phylogenetics and phylogenomics. Current Opinion in Plant Biology9: 1-5.
Haston, E.M., Lewis, G.P. & Hawkins, J.A. (2005). A phylogenetic reappraisal of the Peltophorum group (Caesalpinieae: Leguminosae) based on the chloroplast trnL-F, rbcL and rps16 sequence data. American Journal of Botany, 92: 1359-1371.