Molecular delimitations in the Ehretiaceae (Boraginales)

Abstract

Major taxa of Ehretiaceae (including parasitic Lennoaceae) have not all been included in previous molecular phylogenetic analyses. As a result, the generic limits and their circumscriptions have not been satisfactorily resolved, despite its importance for floristic studies. To clarify which monophyletic groups can be recognized within the Ehretiaceae, sequences from one nuclear (ITS) and three plastid loci (rps16, trnL–trnF, trnS–trnG) were obtained from 67 accessions tentatively assigned to the Ehretiaceae (including 91 new GenBank entries) and covering the known diversity of the group. In phylogenetic analyses, Ehretiaceae were monophyletic when Lennoaceae were included and segregated into nine monophyletic lineages that correspond to accepted, morphologically distinct taxonomic units, namely Bourreria (s.l., paraphyletic in its current circumscription if not including Hilsenbergia), monotypic Cortesia, Ehretia (s.l., paraphyletic in its current circumscription if not including Carmona and Rotula), Halgania, monotypic Lennoa, Lepidocordia, Pholisma, Rochefortia, and Tiquilia. Bourreria and Ehretia have representatives in both the Old World and the New World, but all other taxa are restricted to the tropical and subtropical Americas (Cortesia, Lennoa, Lepidocordia, Pholisma, Rochefortia, Tiquilia) or Australia (Halgania). The historical biogeography of Ehretiaceae can be explained by few colonization events. The molecular trees are also discussed with respect to fruit evolution, where the fusion of endocarp parts may have taken place several times independently.