Phylogeny of Braya and Neotorularia (Brassicaceae) based on nuclear ribosomal internal transcribed spacer and chloroplast trnL intron sequences

Abstract

Sequence data from the nuclear ribosomal internal transcribed spacer (ITS) region and the chloroplast trnL intron were used to examine the evolutionary relationships and generic delimitations of Braya, Neotorularia, Dichasianthus, and Sisymbriopsis. Several species, especially the North American - Asian Braya (= Neotorularia) humilis (C.A. Mey.) B.L. Rob., were previously assigned to more than one genus. Sequence data were obtained from all Braya species, except Braya pilosa Hook., seven species of Neotorularia, one of Dichasianthus, and two of Sisymbriopsis. Maximum parsimony analyses showed a poly phyletic origin for Neotorularia, with the genus split into three or four major clades. For both the ITS and trnL sequence data, three species (Neotorularia brachycarpa (Vassilcz.) Hedge & J. Léonard, Neotorularia gamosepala (Hedge) O'Kane & Al-Shehbaz, and Neotorularia humilis (C.A. Mey.) Hedge & J. Léonard) fell within the Braya clade; Neotorularia korolkowii (Regel & Schmalh.) Hedge & J. Léonard formed a separate clade with Dichasianthus subtilissimus (Popov) Ovcz. & Yunussov, while Neotorularia torulosa (Desf.) Hedge & J. Léonard, Neotorularia contor tuplicata (Stephan ex Willd.) Hedge & J. Léonard, Neotorularia dentata (Freyn & Sint.) Hedge & J. Léonard, and Neotorularia tetracmoides (Boiss. & Hausskn.) Hedge & J. Léonard formed either one clade (trnL data) or two clades (ITS data). Sisymbriopsis was not monophyletic, although ITS and trnL data showed a weakly supported relationship between Sisymbriopsis mollipila (Maxim.) Botsch. and one of the Neotorularia clades. Except for Braya forrestii W.W. Sm., which is well supported as sister to the remainder of the Braya clade (ITS data), ITS and trnL sequences showed poor resolution within Braya. Additive ITS sequences indicated allopolyploid origins for Braya fernaldii Abbe, Braya longii Fernald, and three accessions of Braya glabella Richardson (all species with 2n = 56). Morphology and molecular data strongly suggest expanding Braya to include N. humilis, N. brachycarpa, and N. gamosepala; delimiting Neotorularia to include N. torulosa, N. contortuplicata, N. dentata, N. korolkowii, N. tetracmoides, D. subtilissimus, and S. mollipila; and revising Sisymbriopsis.Key words: Braya, Neotorularia, Dichasianthus, Sisymbriopsis, ITS, trnL, Brassicaceae.