The phylogeny of Alyssum L. (Brassicaceae) inferred from molecular data

10 March 2015

Li, Yan; Feng, Ying; Lv, Guanghui; Liu, Bin; Qi, Aladaer

Previous molecular phylogenetic studies have contributed greatly to the phylogenetic position and infra-generic relationships of the genus Alyssum. Nevertheless, due to sampling and incongruences of 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 with a larger sample collection, which included 171 accessions representing 112 species from five sections. The phylogenetic analyses confirmed the paraphyly and recognition of two main clades in the genus. The first clade included sections Alyssum, Gamosepalum and most species from sect. Psilonema. A. lanigerum from sect. Odontarrhena was inferred to be nested in this clade only by ITS dataset. The other clade contained 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 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 trnL-F dataset. Neither the monophyly of 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.