We used DNA sequences from the nuclear ribosomal internal transcribed spacer (ITS) region and the chloroplast gene matK to examine generic circumscriptions and infer phylogenetic relationships of the grass genus Chloris (Chloridinae: Chlorideae: Chloridoideae) and several related taxa. Our ITS and matK data sets include 36 and 29 species, respectively, and represent at least 13 genera plus three outgroups from the tribe Eragrostideae. Independent and combined analyses of both data sets firmly suggest that Chloris is polyphyletic and should be redefined. However, a clade containing 7-11 Chloris species, Enteropogon dolichostachys, and Lintonia nutans is strongly supported by bootstrap values of 99%. Thus, it appears that Lintonia nutans of subtribe Pommereullinae and Enteropogon dolichostachys should be included in Chloris. Species treated either as a separate genus (Eustachys) or as a subgenus of Chloris (except for C. retusa) form a monophyletic group that is distinct from Chloris and weakly associated with a clade comprising Cynodon + Brachyachne. The relationships among Eustachys, Cynodon-Brachyachne, and Chloris are not clear based on either data set alone or the combined analysis due to an internal polytomy. Additional taxa that have been treated in Chloris and as separate genera, such as Trichloris and Oxychloris, are distinct in these analyses and should be retained. This study forms the phylogenetic foundation for a taxonomic revision of Chloris.

Key words: Chloridoideae, Chloris, ITS, matK, phylogeny, Poaceae