title: Phylogenetic relationships in Brassicaceae tribe Alysseae inferred from nuclear ribosomal and chloroplast DNA sequence data.
abstract: Numerous molecular systematic studies within Brassicaceae have resulted in a strongly improved classification of the family, as morphologically defined units at and above the generic level were often found to poorly reflect phylogenetic relationships. Here, we focus on tribe Alysseae, which despite its size (accounting for about 7% of all species) has only received limited coverage in previous phylogenetic studies. Specifically, we want to test phylogenetic hypotheses implied by current tribal and generic circumscriptions and to put diversification within tribe Alysseae into a temporal context. To this end, sequence data from the nrDNA ITS and two plastid regions (ndhF gene, trnL-F intergenic spacer) were obtained for 176 accessions, representing 16 out of 17 currently recognized genera of the tribe, and were phylogenetically analysed, among others, using a relaxed molecular clock. Due to large discrepancies with respect to published ages of Brassicaceae, age estimates concerning Alysseae are, however, burdened with considerable uncertainty. The tribe is monophyletic and contains four strongly supported major clades and Alyssum homalocarpum, whose relationships among each other remain uncertain due to incongruences between nuclear and plastid DNA markers. The largest genus of the tribe, Alyssum, is not monophyletic and contains, apart from A. homalocarpum, two distinct lineages, corresponding to sections Alyssum, Psilonema, Gamosepalum and to sections Odontarrhena and Meniocus, respectively. Clypeola, whose monophyly is supported only by the plastid data, is very closely related to and possibly nested within the second Alyssum lineage. Species of the genus Fibigia intermingle with those of Alyssoides, Clastopus, Degenia, and Physoptychis, rendering Fibigia polyphyletic. The monotypic genera Leptoplax and Physocardamum are embedded in Bornmuellera.
authors.affiliation: University of Zagreb, Faculty of Science, Department of Botany, Marulićev trg 9a, HR-10000 Zagreb, Croatia. Electronic address: ivana.resetnik@biol.pmf.hr.
authors.forename: Ivana
authors.initials: I
authors.lastname: Rešetnik
authors.forename: Zlatko
authors.initials: Z
authors.lastname: Satovic
authors.forename: Gerald M
authors.initials: GM
authors.lastname: Schneeweiss
authors.forename: Zlatko
authors.initials: Z
authors.lastname: Liber
mesh_terms: D001499:Bayes Theorem; D019607:Brassicaceae / Q000145:classification* / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D019143:Evolution, Molecular; D016013:Likelihood Functions; D008957:Models, Genetic; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant; D021903:DNA, Ribosomal Spacer
keywords: Alysseae; Brassicaceae; ITS; Phylogeny; Taxonomy; ndhF; trnL-F