Oreojuncus, a new genus in the Juncaceae.

Juncus trifidus and J. monanthos, two species traditionally included in section Steirochloa of the Juncaceae, are shown to differ substantially in their morphology from other members of this section. Their relationships with the other groups in this family based on DNA data of selected regions of plastome, chondriome and nrDNA, were examined using phylogenetic analyses of the combined data set of all these DNA regions. The resultant cladograms place J. trifidus and J. monanthos at a very basal position in the Juncaceae. Both the morphology and the phylogenetic analysis support the exclusion of these two species from Juncus and placing them in a separate genus. This genus is described under the name Oreojuncus Záveská Drábková et Kirschner. A detailed comparison with the other genera of the Juncaceae and a key for identifying these genera are provided.