Systematics of the tribe Stipeae (Gramineae) using molecular data

摘要

Internal transcribed spacer (ITS) sequences have been determined for a wide range of stipoid grasses (Poaceae, Pooideae, Stipeae). Nardus was confirmed as the most appropriate outgroup. Anisopogon is consistently included among the stipoid genera. Lithachne and Oryza form a clade and are clearly not close to Stipeae, and there is no support for including Brachyelytrum within Stipeae. Ampelodesmos and Diarrhena do appear among the core taxa in some analyses, but their positions are unstable and the evidence for retaining them is limited. So far there is inadequate support for rejecting them from Stipeae, so they should be included in any comprehensive study of the tribe. The ITS phylogeny supports a narrow interpretation of Jarava, one that includes only species with clear adaptations to anemophilous diaspore dispersal. There is no support for Achnatherum s.l. being a monophyletic group, nor are there any clear and consistent groups within it. Nassella, Hesperostipa, and Piptochaetium remain well supported. The data support some internal groupings within Nassella, but the sample size is small. It maybe worthwhile investigating subgeneric relationships within Nassella. Anemanthele always appears associated with, and sometimes within, Austrostipa, but its position is inconsistent. We recommend continuing to recognize it at the generic level because of its distinctive morphological characters. Stipa s.s. shows some cohesion, but the results also suggest that some species currently included in the genus do not belong in it, suggestions that are supported by other studies. There has been no advance in understanding Piptatherum. The data support some of the subgeneric groupings within Austrostipa, but suggest that others should be combined. Austrostipa subgen. Falcateae is well supported, in part by a shared deletion. Additional species of Stipa s.s. and Piptatherum are being sequenced to broaden the sampling of these two genera.