Phylogenetic relationships within the subtribe Cynoglossinae (Cynoglossoideae: Boraginaceae): new insights from nuclear and plastid DNA sequence data

Cynoglossinae with ca. 200 spp. is one of the taxonomically most challenging subtribes of tribe Cynoglosseae with regard to generic delimitations. Here, we present a phylogenetic analysis based on nuclear ITS and cpDNA trnL-F and rps16 sequences of 270 accessions including 102 newly sequenced ones, representing all currently recognized genera of Cynoglossinae to clarify relationships among Cynoglossum and allied genera. We conducted maximum likelihood, maximum parsimony, and Bayesian inference analyses on separate and combined datasets. Cynoglossinae is recovered as a monophylum of closely related genera. Subtribe Cynoglossinae falls into three major groups: (1) Clade I including Microparacaryum spp., (2) Clade II comprising two species of Lindelofia, several Cynoglossum and Paracynoglossum spp., and (3) a larger clade (Clades III + IV) consisting of Solenanthus, Rindera, Trachelanthus, Paracaryum, Pardoglossum, Mattiastrum, and the remainder of Cynoglossum. None of the genera were monophyletic in the combined nuclear-plastid and nuclear datasets, except for Microparacaryum. A close relationship between Solenanthus apenninus and Cynoglossum officinale is shown, which suggests transferring S. apenninus to Cynoglossum. Moreover, Pardoglossum atlanticum, the type of the genus, is placed within Mediterranean Cynoglossum corroborating its synonymy under Cynoglossum. Lindelofia olgae is distantly related to the type of the genus (L. longiflora), but more closely connected with Solenanthus core-group. The majority of species currently recognized as members of Rindera do not form a clade with the type of the genus (R. tetraspis). The genus Paracaryum as currently circumscribed is paraphyletic and includes some species of Mattiastrum and Rindera.