• Home
• Science Strategy
• Science Teams
• Projects
  • Generic Delimitation in Cyperaceae Tribe Cypereae
• People
• Publications
• Acronyms

Generic Delimitation in Cyperaceae Tribe Cypereae

Cyperus hemisphaericus Boeck. from Zimbabwe. © David Simpson

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 off 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 the unpopular taxonomic view of merging the 15 genera belonging to the ‘Cyperus’ clade into one genus.

Kew has taken a lead in this work having revised one of the larger genera in the ‘Ficinia’ clade (published in 2001-02) and prepared the first molecular phylogenies of Cyperus (2002, with one in press).  We have also identified and described several new species within Cyperus.

We are currently investigating the two groups within the ‘Cyperus’ clade. We want to find out if these groupings are reflected in other genes/gene regions particularly from nuclear DNA. We also want to confirm whether the taxa we have sequenced are C3 or C4 using stable carbon isotope ratios. Collaborative studies on floral development are being undertaken. In addition we need to obtain a larger molecular dataset for tribe Cypereae Tied in with this, and subject 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.

Kew Home | Science Directory | Copyright & Privacy