A new subgenus of Sonchus (Asteraceae: Cichorieae) inferred from molecular data

Abstract

A new subgenus, Sonchus subg. Palustres, is established to accommodate S. erzincanicus endemic to Turkey and former Sonchus ser. Palustres including S. palustris and S. sosnowskyi. Although the exclusive placement of S. palustris has already been documented by previous studies based on molecular phylogenetic analyses without morphological evidence, there has not been any study of S. erzincanicus above the specific level. The present study proposes a new subgenus based on chiefly molecular data, and contribute macro- and micro-morphological features (i.e. pollen grains and achenes) of the studied species together with the phylogenetic position based on nrITS and matK with multiple sampling. Further literature and morphological studies evidently showed that S. erzincanicus and S. palustris have slightly heteromorphic achenes which is a subtle character and underestimated up to now in the infrageneric classification of the genus Sonchus. Besides, the molecular analyses revealed that S. erzincanicus and S. palustris are sister taxa, forming an exclusive clade of their own within the genus. Moreover, the Palustres clade is the first diverged one among the clades of the genus Sonchus based on the nrITS data. Consequently, S. erzincanicus, S. palustris and S. sosnowskyi are treated as members of the suggested new subgenus. Therefore, the slightly heteromorphic achene feature could be taken into consideration for species delimitation in the genus Sonchus as a supportive morphological character. Furthermore, S. araraticus is suggested as a synonym of S. erzincanicus based on its morphological and ecological characteristics.