The delimitation of Senecio series Otopteri (Asteraceae, Senecioneae): a new molecular phylogenetic hypothesis

Abstract

Senecio series Otopteri, as currently circumscribed, consist of thirteen South American species. Previous molecular phylogenetic research showed that series Otopteri is not monophyletic, but these studies only included three Otopteri species. The aim of the research presented here was to use sequence data from two nuclear DNA regions (ITS and ETS) to improve our understanding of the phylogenetic relationships of series Otopteri and propose a revised hypothesis of its delimitation. This study included nine Otopteri species and a broad sampling of other South American Senecio lineages. Our molecular phylogenetic analyses resolved several clades consisting of Otopteri species. As in previous studies, our data show that S. otites is only distantly related to Senecio s.str. and therefore should be excluded from it. Some of the other Otopteri species formed clades with species classified in Senecio series Culcitium and/or Corymbosi. Senecio otopterus composed a clade with four other species classified in series Otopteri, and morphological observations suggest that four Otopteri species that could not be sequenced for this study might also belong to this clade. Awaiting studies aimed at resolving the phylogenetic relationships of series Otopteri using DNA sequences of the plastid genome, we suggest that the S. otopterus clade is used as the basis for a narrower, but monophyletic delimitation of series Otopteri. An updated species list, illustrations, and a key to the species of series Otopteri are presented. In addition, a lectotype is designated for S. sepium.