New Phylogeny of the Caesalpinioideae, Leguminosae
The legume subfamily Caesalpinioideae (as currently circumscribed) comprises 171 genera, a number of which form the basally branching lineage within the legume phylogeny. Using a combination of molecular and morphological data the project aims to reveal inter-generic relationships within the study group that lead to a new phylogeny (and ultimately a new classification) of the Caesalpinioideae in its broadest sense.
Caesalpinia cassioides from the Andes of South America © G. P. Lewis
A robust Caesalpinioideae phylogeny will serve as the basis for a new classification system, and the foundation to explore patterns of morphological and molecular evolution. Although the Leguminosae is traditionally treated as consisting of three subfamilies the problem is that the Caesalpinioideae are not monophyletic. Preliminary analyses demonstrate that while some caesalpinioid lineages are basally branching in legumes, others are more closely related to Mimosoideae or Papilionoideae than they are to other caesalpinioids. Key questions are: 1) How many distinct lineages are there in 'Caesalpinioideae'?, 2) At what level should these be recognised relative to Mimosoideae and Papilionoideae? and 3) What are the relationships among “caesalpinioid” legume genera? Targeted fieldwork aims to fill gaps at the generic level where fresh leaf material is needed for molecular analysis. Once we have a robust phylogeny and a complete specimen-based morphological data set in place we will be in a good position to explore the implications of the phylogeny with respect to patterns of morphological evolution, especially floral structure. In addition, data on a diverse array of fossil legumes will allow us to explore the implications of the palaeobotanical data.
In the past five years Kew has contributed to a multi-disciplinary, international collaboration on the Caesalpinioideae, a programme largely supported by the NSF of the USA. As part of an ongoing gap-filling drive, fieldwork has targeted genera (in Asia, Africa and the Neotropics) not previously included in any molecular studies. A large morphological data matrix has been constructed and a number of genus level studies and subfamily level molecular and combined molecular/morphological analyses have been undertaken and published in a series of internationally co-authored papers.
The project has become part of a larger one co-ordinated by the recently established international Legume Phylogeny Working Group (LPWG) that has as a central goal the production a new classification for the whole legume family.
Key publications 2006-2011
- Sotuyo, S., Delgado-Salinas, A., Chase, M.W., Lewis, G.P. & Oyama, K. (2007). Cryptic Speciation in the Caesalpinia hintonii complex (Leguminosae: Caesalpinioideae) in a Seasonally Dry Mexican Forest. Annals of Botany 100(6): 1307 – 1314.
- Bruneau, A., Mecure, M., Lewis, G.P. & Herendeen, P.S. (2008). Phylogenetic patterns and diversifications in the caesalpinioid legumes. Canadian Journal of Botany 86: 697–718.
- Sinou, S., Forest, F., Lewis, G. & Bruneau, A. (2009). The genus Bauhinia s. l. (Leguminosae): a phylogeny based on the plastid trnL-trnF region. Botany 87: 947 – 960.
- Conceiçao, A.de S., Queiroz, L.P. de, Lewis, G.P., Andrade, M.J.G. de, Almeida, P.R.M. de, Schnadelbach, A.S. & Berg, C. van den (2009). Phylogeny of Chamaecrista Moench (Leguminosae-Caesalpinioideae) based on nuclear and chloroplast DNA regions. Taxon 58: 1168 – 1180.
- Gasson, P., Warner, K. & Lewis, G. (2009). Wood anatomy of Caesalpinia s.s., Coulteria, Erythrostemon, Guilandina, Libidibia, Mezoneuron, Poincianella, Pomaria and Tara (Leguminosae, Caesalpinioideae, Caesalpinieae). IAWA Journal 30(3): 247 – 276.
Project partners and collaborators
Dr Anne Bruneau, University of Montreal
Carole Sinou, University of Montreal
Dr Pat Herendeen, Chicago Botanic Garden
Dr Luciano Paganucci de Quieroz
Dr Jeny Sotuyo
Dr Jan Wieringa
National Science Foundation (grant ended)