Molecular Phylogeny of the Species-Rich Carex sect. Racemosae (Cyperaceae) Based on Four Nuclear and Chloroplast Markers

Carex is one of the most species-rich genera of the world and an important component of vegetation, particularly in colder regions. One of its larger groups is sect. Racemosae with almost 60 species, which are distributed mainly in mountains of the northern hemisphere as well as in the Andes of South America. To address the systematics and evolution of this section and related groups we sampled nearly 80% of the species from all morphological groups previously recognized in the section and estimated their phylogenetic relationships using maximum parsimony, maximum likelihood and Bayesian analyses on a combined nuclear (ITS, ETS) and chloroplast (trnK-matK, rps16) DNA sequence dataset. We observed incongruence only between the chloroplast trnK-matK and the nuclear ETS 1f data and attribute this to a putative parallelism in the chloroplast data set. Our results indicate that sect. Racemosae is not monophyletic in its traditional circumscription. Most species, however, belong to a well-supported clade that is sister to clades consisting of all other sampled species from sections Bicolores, Paniceae, Phacocystis, and Scitae. We recognize eight major clades within the Racemosae, most of them supported by morphological and, in part, geographical data. Previously suggested vicariant distribution patterns between western North American and Eurasian species could not be corroborated. The phylogenetic tree suggests that whereas single morphological characters are highly homoplasious, combinations of characters are nevertheless suitable to recognize clades.