XVI International Botanical Congess

Piptochaetium is an American genus, being scarcely represented in tropical regions. According to recent treatments of the Stipeae, this genus is closely related to Hesperostipa and Nassella s.s. The aims of this study are to complete the taxonomic revision of the genus and to analyze its monophyly and phylogeny. A cladistic analysis was made to evaluate relationships among the 35 species of Piptochaetium, based on approximately 30 morphological characters, including microcharacters ofthe floret. Hesperostipa and Nassella were considered as outgroups.The monophyly of Piptochaetium was confirmed, based on three autapomorphies: palea 2-nerved and grooved, and involute lemma margins included in the groove. The monophyly of its sections is also discussed.