Phylogenetic relationships of Piptochaetium Presl (Poaceae: Stipoideae) and related genera as reconstructed from nuclear and chloroplast datasets.

HAMES, K.; CIALDELLA, A. M.; GIUSSANI L. M.; BARBER, L. C.

Chico, USA

Congreso; Annual meeting of the American Society of Plant Taxonomy: Botany 2006, Looking to the future conserving the past.; 2006

Piptochaetium (Poaceae, Pooideae, Stipeae) is a New World genus of grasses distributed primarily in temperate South America, with several species extending into Central and southern North America. The genus comprises ca. 37 species and 2 subspecies. Morphological synapomorphies include the presence of a longitudinally-grooved palea that is longer than the lemma and protrudes from the lemma apex, and lemma margins that are involute and fitted into the palea groove. The closely related genera Nassella Desv. (116 spp.) and Jarava Ruiz & Pav. (59 spp.) are also primarily South American, with a few species found in Central and North America. Published molecular studies to date have focused upon generic-level relationships within the tribe Stipeae, but none have included more than a few representatives of each genus. We present here results of phylogenetic analyses of these genera based upon DNA sequences of both nuclear (ITS) and cpDNA (trnL; rpl16) markers. Piptochaetium is supported as monophyletic in all studies, but our data cannot clearly distinguish Nassella and Jarava. We compare relationships resolved in the two data partitions (nuclear and combined chloroplast). Several clades are common to both, but there are several well-supported instances of incongruence. Infrageneric relationships of Piptochaetium are also compared to a recent (2002) morphological phylogeny of the genus.