Generic status, circumscription, and allopolyploid origin of Faberia (Asteraceae: Cichorieae) as revealed by ITS and chloroplast DNA sequence data

The Chinese endemic Faberia (Asteraceae: Cichorieae) is imperfectly understood: its generic status, circumscription, and subtribal affiliation have long been in dispute. Here we present a molecular analysis to address these problems. Nuclear (ITS) and plastid (matK, psbA-trnH, rbcL, and trnL-F) sequence data were analyzed by means of Bayesian inference, maximum likelihood and maximum parsimony methods. Our results support the independent generic status of Faberia but not that of Faberiopsis, which should be re-submerged in the former. Dubyaea glaucescens is revealed as a member of Faberia, resulting in a new combination, E glaucescens. The recent addition of Youngia racemifera to Faberia is refuted but the transfer of Prenanthes faberi to Faberia as F. faberi is corroborated. Consequently, Faberia is circumscribed here to include eight species (E cavaleriei, F ceterach, F. faberi, E glaucescens, E lancifolia, E nanchuanensis, F. sinensis, F thibetica). Most notably, phylogenies based on nrITS and cpDNA sequence data are highly incongruent with respect to the subtribal relationship of Faberia. The ITS phylogeny locates the genus in Lactucinae, whereas the cpDNA phylogeny places it in Crepidinae. This incongruence, together with karyological (Faberia has x = 17, a very rare number in Cichorieae) and palynological (Faberia has larger, 4-porate pollen grains, which are associated with polyploidy in Cichorieae) data, strongly favors the hypothesis that Faberia may have originated via hybridization between a member of Lactucinae with x = 9 (paternal parent or pollen donor) and a member of Crepidinae with x = 8 (maternal parent or ovule donor) and subsequent polyploidization. This work greatly increases our knowledge of Faberia and provides a convincing example of allopolyploid origin at the generic level within Cichorieae.