Strong biogeographic signal in the phylogenetic relationships of Rochefortia Sw. (Ehretiaceae, Boraginales)

Dioecious and thorny Rochefortia Sw. is a poorly known though distinct element of the Ehretiaceae comprising woody plants restricted to the Caribbean and the adjacent American mainland. The approximately ten species display a great morphological variability and overlapping taxonomic boundaries, which makes it difficult to differentiate them (particularly in the Caribbean region). We investigated the phylogenetic relationships of Rochefortia using DNA sequence data from one nuclear locus (Internal Transcribed Spacer) and three chloroplast DNA loci ( rps 16, trn L– trn F, trn S– trn G). The monophyly of Rochefortia was confirmed, with a sister group relationship between an American mainland clade and a Caribbean clade. The latter segregates into three, morphologically rather variable lineages, distributed either in the Lesser Antilles or in the eastern Greater Antilles or in the western Greater Antilles. Thus, geographic occurrence rather than morphology is indicative of taxonomic delimitation in Rochefortia .