Monophyly, phylogenetic position and the role of hybridization in Schoenoxiphium Nees (Cariceae, Cyperaceae)

Incongruence between gene trees, even within genomes, is often the result of hybridization and/or other processes such as incomplete lineage sorting, and can cause problems for phylogenetic analyses. We show here that the radiation of the Cyperaceae genus Schoenoxiphium involved at least one hybridization event with a closely related species of Carex, as indicated by a recombinant nuclear ITS region shared by all species in the S. rufum clade and C. camptoglochin. Recombinant sequences were confirmed with cloning experiments and recombination analyses. The monophyly of Schoenoxiphium has, in previous analyses, been suspected but not sufficiently supported, possibly due in part to this problem. Our phylogenetic analyses include an appropriate representation of Schoenoxiphium and other related Cariceae species and an extended sampling of the nuclear ITS and plastid marker regions, trnLF and rps16. We demonstrate that Schoenoxiphium is monophyletic, nested within Carex, and that several supported clades exist in Schoenoxiphium.