Systematic Study of Tribe Indigofereae (Leguminosae: Papilionoideae)
The economically important indigo dye genus Indigofera is the third largest genus in the family Leguminosae, and occurs throughout the tropics of the world with more than 750 species.
Indigofera hebepetala. Photo: B. Schrire.
The tribe Indigofereae (Leguminosae – Papilionoideae) comprises six genera and c. 800 species. The Madagascan dry forest Disynstemon is resolved as sister to the tribe, and Phylloxylon, another Madagascan dry forest endemic, is resolved as sister to the rest of the tribe. A clade containing Cyamopsis, Indigastrum, Microcharis, and Rhynchotropis (CRIM clade) is sister to Indigofera. All species of the genus Indigofera comprise just four well supported clades, each of which is diagnosable with derived morphologies and ecological and geographical predilections. Indigofera,with a worldwide distribution and c. 750 species, is the third largest genus in legumes. Centres of diversity occur primarily in Africa and Madagascar (c. 550 species), Asia, especially the temperate Sino-Himalayan region (c. 105 species), Australia (c. 50 species), and the New World (c. 45 species). The results of recent phylogenetic analyses of the tribe suggest that niche conservation (ecology) and dispersal limitation (geography) are important processes rendering signature shapes to the Indigofereae phylogeny in different biomes. Clades confined to temperate and succulent-rich biomes are more dispersal limited and have more geographical phylogenetic structure than those inhabiting tropical grass-rich vegetation. The African arid corridor, particularly the Namib centre of endemism, harbours many of the oldest Indigofera lineages. A rates analysis of nucleotide substitutions confirmed that the ages of the oldest crown clades are mostly younger than 16 Ma, including the three amphi-Atlantic disjunct clades, implicating dispersal in explaining the worldwide distribution of the tribe.
The next phase of research is aimed at developing a mobile application and computer field identification guide to Indigofera in southern Africa (c. 320 spp.), where the entry point is a map of the region divided into quarter degree square grids. The underlying data of species occurring in each grid is derived from a fully verified PRECIS database, with collections added from other relevant herbaria. By pointing at an appropriate grid square in the field (or entering a GPS reading), the intention is to get a subset (A List) of the Indigofera species recorded from that grid. A second layer comprises a digitised version of the Vegetation Atlas of South Africa, Lesotho & Swaziland (Mucina & Rutherford, 2006) and similar digitised vegetation maps for Botswana and Namibia. Vegetation types identified by actual species occurrences are then, for each species, converted into quarter degree square grid maps covering the full extent of all included vegetation types. This will generate a B List of species that are likely to occur from any one of the quarter degree squares making up that vegetation type map. A C List of possible or less likely species to be found in a grid would be generated by expanding the grid map of vegetation types identified in the B List to neighbouring vegetation types considered to have a reasonable probability of also containing that species. A third layer would be a LUCID interactive key customised to include diagnostic characters and images of all Indigofera species in southern Africa so that species in the A,B and/or C Lists, or indeed any unidentified species, can be keyed out quickly.
Key publications 2006-2011
- Lewis, G.P., Klitgaard, B.B. & Schrire, B.D. (2006). Seasonally dry forests of southern Ecuador in a continental context: insight from legumes. In R.T. Pennington, G.P. Lewis & J.A. Ratter (eds.) Neotropical savannas and seasonally dry forests: plant diversity, biogeography and conservation. Boca Raton: CRC, Taylor & Francis, Boca Raton. 281–314.
- Schrire, B.D., Lavin, M., Barker, N.P. & Forest, F. (2009). Phylogeny of the tribe Indigofereae (Leguminosae–Papilionoideae): Geographically structured more in succulent-rich and temperate settings than in grass-rich environments. American Journal of Botany 96(4): 816–852.
- Ireland, H.E., Kite, G.C., Veitch, N.C., Chase, M.W., Schrire, B., Lavin, M., Linares, J. & Pennington, R.T. (2010). Biogeographical, ecological, and morphological structure in a phylogenetic analysis of Ateleia (Swartzieae-Fabaceae) derived from combined molecular, morphological and chemical data. Bot. J. Linn. Soc. 162: 39–53.
- Warren, B.H., Bakker, F.T., Bellstedt, D.U., Bytebier, B., Claßen-Bockhoff, R., Dreyer, L.L., Edwards, D., Forest, F., Galley, C., Hardy, C.R., Linder, H.P., Muasya, A M., Mummenhoff, K., Oberlander, K.C., Quint, M., Richardson, J.E., Savolainen, V., Schrire, B.D., Van der Niet, T., Verboom, G.A., Yesson, C., Hawkins, J.A. (2011). Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora. BMC Evolutionary Biology 11:39 (1–11) (open access)
- Davies, T.J., Smith G.F., Bellstedt, D.U., Boatwright, J.S., Bytebier, B., Cowling, R.M., Forest, F., Harmon, L.J., Muasya, A.M., Schrire, B.D., Steenkamp, Y., Van der Bank, M. & Savolainen, V. (2011). Extinction risk and diversification are linked in a plant biodiversity hotspot. PLoS Biol. 9(5): e1000620 (open access)
Project partners and collaborators
Nigel Barker, Rhodes University, South Africa
Matt Lavin, Montana State University