New circumscription of the genus Gamochaeta (Asteraceae, Gnaphalieae) inferred from nuclear and plastid DNA sequences

LÓPEZ, ALICIA ; BAEZA, CARLOS M. ; CHEMISQUY, MARÍA A. ; MOREIRA, ANDRES ; BAYÓN, NÉSTOR DAVID ; SALOMÓN, LUCIANA; NESOM, GUY L. ; FREIRE, SUSANA ; URTUBEY, ESTRELLA ; ANDERBERG, ARNE ALFRED ; PAZ DEBLE, LEONARDO ; ALFORD, MAC H.

PLANT SYSTEMATICS AND EVOLUTION

SPRINGER WIEN

Lugar: Viena; Año: 2016 vol. 13 p. 1 - 20

0378-2697

Gamochaeta(tribe Gnaphalieae, Asteraceae) iscomposed of ca. 60 species primarily distributed in tropicaland subtropical America. Within the tribe Gnaphalieae, thegenus is characterized by capitula arranged in spikes orhead-like clusters, few hermaphroditic central florets,truncate style branches with apical sweeping trichomes,pappus bristles connate at the base into a ring falling as aunit, and achenes with globose twin trichomes. Previousmolecular phylogenetic studies have suggested the para-phyly of the genus, but have not provided a basis forredefining generic limits due to incomplete taxon sampling.To address this problem, DNA sequences from the plastid(trnL-F) and nuclear (ETS and ITS) genomes were ana-lyzed from a broad taxon sample representing the full rangeof morphological variation known in the genus. Our resultsaffirm thatGamochaetais paraphyletic as presently cir-cumscribed. Two clades can be recognized: one clade thatincludes the majority of the species currently assigned toGamochaetaand a second clade that includesGamochaetopsis,Stuckertiellaand seven species ofGamochaeta.We present here a new circumscription ofGamochaeta, including two new combinations,Gamo-chaeta alpinaandGamochaeta peregrina,and the resur-rection ofGamochaeta capitata. Our results also showOmalotheca supina,O. norvegicaandO. sylvatica, whichwere placed by some authors inGamochaetaor inGnaphalium, form a monophyletic group distantly relatedto both genera.