The phylogeny of Alyssum (Brassicaceae) inferred from molecular data

Previous molecular phylogenetic studies have contributed greatly to our knowledge about the phylogenetic position and infra-generic relationships of the genus Alyssum. Nevertheless, due to limited sampling and incongruences between the different markers used, the phylogenetic relationships within the genus are still unresolved. In this study, the phylogenetic relationships within Alyssum were studied using nrDNA ITS and plastid trnL-F sequences from 171 accessions representing 112 species from five sections of the genus. The phylogenetic analyses confirmed the paraphyly and recognition of two main clades in the genus. The first clade included the sections Alyssum, Gamosepalum and most species from sect. Psilonema. Alyssum lanigerum from sect. Odontarrhena was inferred to be nested in this clade only by the ITS dataset. The other clade contained the sections Meniocus, Odontarrhena and the genus Clypeola. The monophyly of the five sections defined by morphology was not well supported by molecular data. Species of the sections Gamosepalum and Psilonema (apart from A. homalocarpum) were intermixed with species of sect. Alyssum, and the monophyly of sect. Meniocus and the genus Clypeola were supported only by the trnL-F dataset. Neither sect. Odontarrhena nor that of its three subsections, subsect. Inflata, Compressa and Samarifera, were recovered as monophyletic. The incongruence between morphology and molecular data indicates that the current taxonomic circumscription of the genus and sections need to be revised.