Molecular phlogeny of Fibigia (Brassicaceae) and allied genera

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. Recently the study of tribe Alysseae provided insight into the generic circumscriptions of one of the largest tribes within Brassicaceae, which harbours about 7% of the family’s species diversity. One of the identified monophyletic clades was the Fibigia clade encompassing several species poor genera, namely Alyssoides, Clastopus, Degenia, Fibigia and Physoptychis. The genera within the clade are mainly distributed within Irano-Turanian floristic region, with some taxa occurring in the Mediterranean region and the majority of species exhibiting a narrow geographic range (“narrow endemics”). Morphologically, species of this clade are characterized by being perennial herbs, subshrubs or shrubs with an indumentum of stellate hairs sometimes mixed with simple ones, relatively large yellow or purple flowers and large fruits with mostly winged seeds. Additionally, this clade encompasses greater fruit diversity than the rest of the tribe ; being dehiscent or indehiscent, inflated fruits or strongly compressed, with papery, leathery or thickened valves. The initial phylogenetic analysis revealed that the largest genus in the clade, Fibigia was not monophyletic and the relationships among genera were poorly resolved and burdened with incongruences among markers. In order to provide further insight into phylogenetic relationships we included additional taxa, encompassing the majority of species in the clade. To this end, we obtained sequence data from the nrDNA ITS and ndhF gene plastid region. The non-monophyly of Fibigia was confirmed and six lineages were identified. Most lineages were strongly supported and included only one species supporting the taxonomical recognition of additional monotypic genera. However, F. afghanica, F. membranacea and F. multicaulis were intermingled with genera Clastopus and Straussiella indicating complex phylogenetic relationships. Separation of genus Alyssoides into monotypic Alyssoides including A. utriculata and monotypic Lutzia with L. cretica was also confirmed.