Phylogenetic relationships among Dorema, Ferula and Leutea (Apiaceae: Scandiceae: Ferulinae) inferred from nrDNA ITS and cpDNA noncoding sequences

Dorema, Ferula and Leutea are genera of Apiaceae tribe Scandiceae, subtribe Ferulinae. Their placement in Scandiceae was established based only on nuclear ribosomal DNA internal transcribed spacer (nrDNA ITS) sequence variation. Previous molecular studies suggested that Dorema and Leutea are nested within Ferula. To confirm relationships and eventual nomenclatural changes, we increased taxonomic sampling and examined nrDNA ITS and three noncoding cpDNA markers: rpoB-trnC intergenic spacer and rps16 and rpoC1 introns. Ninety-one species were included representing 68 species of Ferula, 6 species of Dorema, 9 species of Leutea and 8 outgroup taxa. Nuclear and plastid DNA data were analysed separately and combined using maximum likelihood and Bayesian approaches; based on the set of Bayesian trees several topological hypotheses on relationships among these genera were tested. As nrDNA and cpDNA gene trees differed somewhat, the degree of topological conflict was assessed using internode certainty (IC) and tree certainty (TC) measures calculated from ML bootstrap analyses. In all analyses, Leutea was monophyletic. In nrDNA trees it was nested within Ferula (with low support), while in cpDNA it was sister to the Ferula + Dorema clade. In all analyses, Dorema species were placed in one subclade of Ferula and intermingled with its members. IC support for the sister position of Leutea to remaining Ferulinae and the TC support were higher in combined analyses than in the analyses of cpDNA data alone, indicating that the gene trees are not significantly different with respect to this internode. Our results do not contradict the taxonomic position of Leutea as a separate genus but suggest that Dorema should be subsumed within Ferula.