Vickia, a new genus of tribe Gochnatieae (Compositae)

Abstract

The tribe Gochnatieae is restricted to America. A recent molecular study including over 60% of the species of the tribe was carried out to untangle evolutionary relationships among the taxa. Eight supported clades were recovered as monophyletic genera, while Gochnatia s.l. was revealed as paraphyletic and currently restricted to the Central Andes. Gochnatia rotundifolia was not included in this phylogeny since extracted DNA from few and old collections from Brazil was unusuable. Since Cabrera's treatment of Gochnatia s.l., this species has received special attention due to its distinct morphological characters when compared with the other monophyletic genera of Gochnatieae. Therefore, this paper aims to provide new evidence that supports Gochnatia rotundifolia to be described as a separate monospecific genus based on a morphological study and a maximum parsimony (MP) analysis. A total of 21 species were studied. The leaf venation was analysed using digital X-ray capture (VIVA-Varian Image viewing & Aquisition). Seventeen morphological characters obtained from vegetative and floral parts of the plants were included in the data matrix. Our results reinforce the placement of Gochnatia rotundifolia within the tribe Gochnatieae. Gochnatia rotundifolia is consistently recovered in a clade as sister to the Cnicothamnus-Richterago group. The species differs from the other genera of the tribe by an actinodromous basal leaf venation with three primary veins, and pappus elements composed by (50-)60-75 bristles, sometimes almost flat setae, arranged in 2 or 3 series, unequal in length. Our results support Gochnatia rotundifolia as the sole species Vickia rotundifolia comb. nov. in a new genus of Gochnatieae, Vickia gen. nov. The new genus is described, illustrated, and a generic identification key for the tribe Gochnatieae is provided.