Generic Delimitation in Cyperaceae Tribe Cypereae
Cyperaceae tribe Cypereae comprises c. 900 species in 19 genera. Most of the genera are identified by only a few distinguishing characters, causing problems of generic delimitation. The best known example of this is the debate over whether Cyperus should be broadly or narrowly defined to include or exclude related genera such as Kyllinga, Mariscus or Pycreus within its circumscription.
Ongoing DNA studies support Cypereae as monophyletic, comprising the ‘Cyperus’ and ‘Ficinia’ clades. The ‘Cyperus’ clade, in which the taxa predominantly have distichous glumes, is not monophyletic and two groups are resolved within it that differ in the presence or absence of C4 Kranz anatomy, but without any defining morphological characters. Taxa in the ‘Ficinia’ clade predominantly have spirally-arranged glumes arrangement although some taxa with distichous glume arrangements have previously been included in Cyperus. Hellmuthia, previously included among the Mapanioideae due to the presence of two floral scales, is resolved within the ‘Ficinia’ clade, although the homology of these scales is not yet understood. DNA work has revealed characteristic evolutionary patterns within the tribe, pointing to the need for a revised tribal circumscription and supports merging the 15 genera belonging to the ‘Cyperus’ clade into one genus.
A broader phylogeny of Cypereae was published in 2009 and we have recently collaborated on a closer phylogenetic study of C3 Cyperus lineages. We continue to identify and describe new species within Cyperus and work closely with overseas collaborators on a larger phylogeny.
Tied in with the above, and subject to funding, we wish to investigate why weedy species of Cyperus (such as Cyperus rotundus, known as the ‘world’s worst weed’) are so successful. Despite their economic importance and wide distribution, nothing is known about their evolution or how they accumulated their weedy characteristics.
Key papers published since 2006.
- Larridon, I., Reynders, M., Huygh, W., Bauters, K., Van de putte, K., Muasya, A.M., Boeckx, P., Simpson, D.A., Vrijdaghs, A. & Goetghebeur, P. (2011). Affinities in C3 Cyperus lineages (Cyperaceae) revealed using molecular phylogenetic data and carbon isotope analysis. Botanical Journal of the Linnean Society 167: 19–46.
- Reynders, M., Huygh, W., Larridon, I., Muasya, A.M., Govaerts, R., Simpson, D.A. & Goetghebeur, P. (2011). Nomenclature and typification of names of genera and subdivisions of genera in Cypereae (Cyperaceae): 3. Names of subdivisions in segregate genera of Cyperus. Taxon 60(3): 885-895.
- Lunkai, D. Tucker, G.C. & Simpson, D.A. (2010). Cyperus. In: Wu Zhengyi, Raven, P.H. & Hong Deyaun (eds), Flora of China 23, pp. 219-241. Science Press, Beijing & Missouri Botanical Garden Press, St Louis.
- Huygh, W., Larridon, I., Reynders, M., Muasya, A. M., Govaerts, R., Simpson, D.A. & Goeghebeur, P. (2010). Nomenclature and typification of names of genera and subdivisions of genera in Cypereae (Cyperaceae): 1. Names of genera in the Cyperus clade. Taxon 59(6): 1883–1890.
- Muasya, A.M., Vrijdaghs, A., Simpson, D.A., Chase, M.W., Goetghebeur, P. & Smets, E. (2009). What is a genus in Cypereae: phylogeny, character homology assessment and generic circumscription in Cyperaceae tribe Cypereae. Botanical Review 75: 2-21.
Project partners and collaborators
University of Ghent
University of Cape Town