Phylogeny and classification of Carex section Ovales (Cyperaceae)

Section Ovales is the most species-rich section of the sedge genus Carex in the New World. Phylogenetic analyses of molecular data recover a predominantly New World clade as sister to a solitary east Asian species, C. maackii. Nuclear ribosomal DNA are congruent in the placement of all taxa within the section, with a solitary exception: incongruence between ITS and ETS data in the placement of C. bonplandii and C. roraimensis suggests a hybrid origin for this lineage. Biogeography correlates strongly with phylogeny in the section, but there have been at least two instances of long-range dispersal, one from an eastern North American clade to western North America and one from the New World to Eurasia. Morphological characters studied are all homoplastic. Developing a comprehensive infrasectional classification with a phylogenetic basis would be complicated by the fact that most of the novel morphological characters in the section have evolved within relatively small, independent clades.