Grasses of the Intermountain Region

CYNODONTEAE

174 CHLORIDOIDEAE The subfamily Chloridoideae is most abundant in dry, tropical and subtropical regions. In North America, it reaches its greatest diversity in the southwestern United States (Barkworth and Capels 2000). Almost all its members, and all those in North America, have C4 photosynthesis. Most employ the NAD-ME or PCK pathways, but Pappophorum utilizes the NADP-ME pathway. The subfamily has been recognized, with essentially the same limits as here, for some time, although reservations have been expressed concerning its monophyly (Campbell 1985; Jacobs 1987; Kellogg and Campbell 1987). More recent studies, both morphological (Van den Borre and Watson 1997, 2000) and molecular (Grass Phylogeny Working Group 2001; Hilu and Alice 2001, Bouchenak-Khelladi et al. 2008) support its recognition as a monophyletic unit. There is less agreement concerning the subfamily’s closest relative, some studies pointing to the Arundinoideae (Grass Phylogeny Working Group 2001) and some to the Danthonioideae (Barker et al. 1995; Hilu and Esen 1993; Hilu and Alice 2001, Bouchenak-Khelladi et al. 2008). There is considerable disagreement concerning the tribal treatment within the Chloridoideae, the number of tribes recognized varying from two (Prat 1936) to eight (Gould and Shaw 1983). Hilu and Wright (1982, p. 28) concluded, on the basis of their morphological study, that “... the boundaries between most of the tribes in this subfamily are not pronounced.” They noted that Savile (1979) reached the same conclusion from considering the host specificity of various pathogenic fungi. Subsequent work has not resolved the issue (see, e.g., Hilu and Alice 2001 and Bouchenak-Khelladi et al. 2008). The treatment presented here is conservative in recognizing Pappophoreae as a distinct tribe. It departs from most other treatments in merging all other North American taxa into a single tribe, the Cynodonteae. Consensus on how the Cynodonteae sensu lato should be broken up is unlikely to be reached until the generic limits of its members have been more thoroughly examined. 1. Lemmas 1–11-veined, unawned or with 1 or 3 awns, sometimes with hyaline lobes on either side of the central awns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10. Cynodonteae 1. Lemmas 5–13-veined, all the veins extending into awns, often alternating with hyaline lobes or teeth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. Pappophoreae 10. CYNODONTEAE Dumort. Mary E. Barkworth Pl ann or per. Clm 1–500 cm, not woody, usu not brchd above the base. Shth usu open, often with coarse hairs at the top; aur rarely present; lig of hairs or memb, if memb, often ciliate, cilia smt longer than the memb base; bld often with stiff, coarse mrgl hairs adjacent to the lig, glab or variously pubescent elsewhere. Infl tml, smt also axillary, simple pan, pan of 1–many spikelike br, spikelike rcm, spikes, or, in 1 species, a solitary spklt, in dioecious taxa the stmt and pist infl smt morphologically distinct; dis usu beneath the ftl flt or the glm but, particularly if the pan br are short, smt at the base of the br. Spklt usu lat compressed, with 1–60 flt, strl or rdcd flt, if present, usu distal to the bisex flt. Glm from shorter than the adjacent flt to exceeding the distal flt; lm 1–3-veined or 7–13-veined, rarely 5-veined, if with 7–13 veins, the veins often in 3 groups; lod 2, or absent. x = 7, 8, 9, 10, 12. Most members of the Cynodonteae in the Intermountain Region can be recognized by their possession of two or more of the following characteristics: 1–3- or 7–13-veined lemmas, laterally compressed spikelets, spikelike inflorescence branches, and the presence of coarse hairs near the junction of the sheath and blade. All employ the NAD-ME or PCK C4 photosynthetic pathways, have Kranz blade anatomy, and tend to grow in hot, dry areas. Having said this, it must be acknowledged that each of these characteristics can be found in other tribes and, within the Cynodonteae, there are genera that lack one or more of them. The tribe Cynodonteae, as interpreted here, includes genera that are normally placed in two tribes, the Cynodonteae sensu stricto, and the Eragrostideae Stapf (Clayton and Renvoize 1986; Peterson et al. 2001; Grass Phylogeny Working Group 2001, but see Campbell 1985). Genera 10.01 to 10.18 correspond to the Eragrostideae and genera 10.19 to 10.26 to their Cynodonteae. The two are treated as one here because recent morphological, anatomical, and molecular studies (Van den Borre 1994; Van den Borre and Watson 1997; Hilu and Alice 2001, Bouchenak-Khelladi et...