Phylogeny of New World Stipeae (Poaceae): an evaluation of the monophyly of Aciachne and Amelichloa

CIALDELLA, A.M.; SALARIATO, D.L.; AAGESEN, L.; GIUSSANI, L.M.; ZULOAGA, F.O.; MORRONE, O.

CLADISTICS (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010 vol. 26 p. 563 - 578

0748-3007

The tribe Stipeae, with nearly 550 species, includes 28 core genera, of which 13 occur in America: Achnatherum, Aciachne, Amelichloa, Anatherostipa, Hesperostipa, Jarava, Nassella, Ortachne, Oryzopsis, Pappostipa, Piptatherum, Piptochaetium, and Ptilagrostis. Based on 37 species representing 14 Stipeae genera and using four chloroplast markers and morphological characters, we provide a phylogenetic hypothesis of the New World Stipeae, with our focus on Amelichloa and Aciachne. Parsimony analyses included two aproaches: a) a multiple-sequence alignment where gaps were treated as missing or coded, b) using direct sequences by direct optimization as implemented by POY. Analyses under direct optimization were conducted using the molecular datasets independently and combined, and with morphological data. Different cost regimes were explored and that producing the highest congruence between partitions was chosen. Among the genera considered, only Piptochaetium, Austrostipa, and Hesperostipa resolved as monophyletic, while Achnatherum, Amelichloa s.l., Anatherostipa, Jarava, and Nassella were polyphyletic, and Aciachne was polyphyletic or paraphyletic. As a result, Amelichloa can be restricted to a monophyletic clade if including A. brachychaeta, A. ambigua, A. clandestina, and A. caudata, or it should be considered within Nassella. The phylogenetic position of species of Aciachne suggests inbreeding and outbreeding events with species of Anatherostipa, Ortachne and Hesperostipa.