| With approximately 2000 species, Carex is the largest genus in the Cyperaceae and is one of the most widespread genera in the world. This study focused on two primary goals: to create a hypothesis of relationships for the Cariceae tribe, and to assess relationships within Carex section Acrocystis. Acrocystis traditionally has include 45 to 49 species that predominantly inhabit dry forest understory and that range across temperate North America and Eurasia, with one species in the Andes Mountains of South America. Relationships within Carex and among the genera of the Cariceae (Carex, Cymophyllus, Kobresia, Schoenoxiphium, and Uncinia) were assessed using molecular phylogenetic tools including the nrDNA internal transcribed spacer region (ITS) and cpDNA trn-L-F spacer sequences. Studies within Acrocystis employed the ITS and the nuclear alcohol dehydrogenase (Adh) gene family. Results of this study suggest that the Cariceae form three main clades: (1) Carex subgenus Vignea; (2) Carex subgenus Primocarex (in part) plus the genera Cymophyllus, Kobresia, Schoenoxiphium, and Uncinia; and (3) Carex subgenera Carex, Indocarex, and Primocarex (in part). Carex section Acrocystis is not monophyletic, with the North American and some of the Eurasian species forming a clade, and several of the Eurasian species not associated with this primary clade. The ITS data suggest that the Acrocystis clade is composed of two primary lineages: one associated exclusively with eastern North American species and the other composed of the western North American species, plus some eastern North American species and a few Eurasian species. The Adh gene family is composed of two loci in Carex and supports many of the results of the ITS study, but provides a complicated picture of relationships in the section. Given the topology of the Adh gene phylogeny, lineage sorting and/or hybridization are likely obscuring the phylogenetic relationships of Acrocystis species. |
