Can we rescue <i>Centranthus</i> (Caprifoliaceae: Valerianoideae) from the <i>Valeriana</i> sea?

Abstract Centranthus is a small Mediterranean taxon that was recognized as a distinct genus throughout the 19th and 20th centuries, but initially and more recently was included in Valeriana. The authors propose a molecular phylogenetic study involving all the species and subspecies in Centranthus and confirming its monophyly. Two datasets were used for the phylogeny based on nuclear and plastid markers with Sanger sequencing. The first dataset (DS-I) was based on the nuclear rRNA cistron and 10 plastid markers (five genes, three introns, and two intergenic spacers) and was integrated with literature data for a wide sample of Valerianoideae; the second dataset (DS-II) involved an additional analysis exclusively focused on Centranthus taxa, incorporating five additional plastid markers (four intergenic spacers and one gene) to achieve better resolution within this group. According to the results, the Spanish endemic V. longiflora is identified as the closest living relative of Centranthus. Despite previous hypotheses, Centranthus reliably originated in western continental Europe not in the Sardo-Corse system; in addition, two different lineages precociously originated, one including all and only the annual species, and the other including all and only the perennial ones. All our analyses suggest that the Centranthus clade is nested within a larger Valeriana with extremely strong support. Therefore, and given the relationship with V. longiflora, with the present state of knowledge, the separation of Centranthus from Valeriana appears at least to be not well justified.