A morphology-based cladistic analysis of the Xanthocephalum group (Asteraceae, Astereae)

BARTOLI A; RUA GH; KATINAS L; TORTOSA RD

San Miguel de Tucumán, Argentina

Simposio; XXVII International Meeting of the Willi Hennig Society and VIII Reunión Argentina de Cladística y Biogeografía; 2008

Willi Hennig Society

The so-called ‘Xanthocephalum-group’ comprises 6 or 7 genera (according to different authors) of the Astereae (Asteraceae), characterized by yellow ray florets (if present), corollas of disk florets abruptly ampliate into the throat and basic chromosome number x=6. It includes North and South American representatives. To test the monophyly of both the Xanthocephalum-group as a whole and each of the genera included in it, a morphology-based phylogenetic analysis was conducted using parsimony under implied weights. Analyses were performed under 33 different k values and the resulting topologies were summarized as a majority rule consensus tree. All genera except Grindelia resulted monophyletic across the range of k values tried. Olivaea was nested within Grindelia. Haplopappus and Grindelia were sister groups, and some South American Grindelias were basal to the remainder of the genus. Nevertheless, other South American species were nested deeply within the genus. Monophyly of the Xanthocephalum-group as a whole was not confirmed, since Gutierrezia was placed within it in about 50% of the topologies. A more comprehensive taxon sampling comprising the whole tribe Astereae would be necessary to assess the phylogenetic relationships between the Xanthocephalum-group and the related species in the tribe.