With approximately 2,000 species, Carex is the largest genus in the Cyperaceae and is one of the most widespread genera in the world. Relationships within Carex and among the genera of the Cariceae (Carex, Cymophyllus, Kobresia, Schoenoxiphium, and Uncinia) are unclear. For this reason, a molecular phylogenetic study employing nrDNA ITS and cpDNA trnT-L-F spacer sequences was undertaken. In addition to creating hypotheses of relationship for the Cariceae and testing classifications of this tribe, a primary goal of this study was to assess relationships within Carex section Acrocystis and identify a monophyletic group for more detailed study. These analyses suggest that Cymophyllus, Kobresia, Schoenoxiphium, and Uncinia are nested within Carex. Three primary clades are suggested: a Carex subgenus Vignea clade, a clade including Carex subgenus Primocarex (for the most part) and the other genera of Cariceae, and a clade predominately comprised of Carex subgenera Carex and Indocarex. A large part of Carex section Acrocystis forms a monophyletic group but several Eurasian species are more closely related to other groups rather than to this core clade. Assessment of chromosome number variation across the Cariceae clade suggests that the ancestor of the Cariceae had a moderate to high chromosome number. In addition, these analyses suggest the sister group of the Cariceae is a clade including Scirpus sensu stricto, Amphiscirpus, and Dulichium.

Communicating Editor: Jeff H. Rettig