Salcedoa gen. nov., a biogeographic enigma in the Caribbean Mutisieae (Asteraceae)

Abstract

A new genus, Salcedoa, is described from the Cordillera Septentrional, in the northern Dominican Republic. The bilabiate florets, smooth style branches, caudate anthers, and the size, shape, exine structure, sculpture, and endoaperture form of its pollen grains place it close to the South American genera of the tribe Mutisieae (Asteraceae), which are centered in the Guayana Shield. Two morphology-based phylogenetic analyses—one using Gochnatia and the other Chaetanthera as outgroups—were conducted, including Salcedoa and the 12 Guayanan genera, to determine the sister-group relationships of Salcedoa. The results suggest that Salcedoa is sister to Gongylolepis. The unusual distribution pattern of Salcedoa and the Guayanan genera was examined through the dispersal–vicariance method, leading to the hypothesis of a trans-oceanic fruit dispersal as the probable mechanism by which Salcedoa reached Hispaniola from a South American ancestor.