HILU, KHIDIR W.* AND LAWRENCE A. ALICE. Department of Biology, Virginia Tech, Blacksburg, Virginia, 24061, and , Department of Biology, Western Kentucky University, Bowling Green, Kentucky, 42101. - Addressing and raising new systematic questions in the Chloridoideae (Poaceae) with matK sequence data.
Monophyly, origin and systematics of the subfamily Chloridoideae have
long been debated. We present evidence from the plastid matK
gene sequences of 74 species representing 55 genera and all tribes,
and from extensive outgroup survey to address these questions. The
monophyly of the Chloridoideae and its origin from an arundinoid group
with C4 photosynthesis are unequivocally ascertained by
this study. Rooted with the arundinoid Centropodia, a basal
polytomy was observed among Triraphis schlecteri and three
strongly supported clades labeled A, B, and C. Clade A comprises the
Pappophoreae, Uniolinae, and three Eragrostideae genera; clade B
includes most representatives of subtribe Sporobolinae, Spartina,
Zoysia, and some Eragrostis; and clade C encompasses the
remaining taxa. The two largest tribes Eragrostideae and
Chloridoideae are polyphyletic. Uniolinae, Orcuttieae and Triodiinae
form strongly supported monophyletic entities. The taxonomic status
of other tribes is discussed. Two large genera, Chloris and
Eragrostis, do not appear monophyletic. A repeated pattern of
segregation of Old World from New World taxa is evident. The results
provide a framework for further detailed studies at the tribal and
generic levels to reach a comprehensive systematic treatment of the
Chloridoideae.
Key words: Chloridoideae, matK, molecular, phylogeny, Poaceae, systematics