Phylogenetic relationships of Vulpia and related genera (Poeae, Poaceae) based on analysis of ITS and trnL-F sequences

A phylogenetic study of Vulpia, fine-leaved Festuca (Festuca subg. Festuca p.p.), and other related genera of the tribe Poeae (Poaceae) has been conducted using both separate and combined analyses of DNA sequences from the nuclear ITS region and the chloroplast trnL-F region. All five sections of Vulpia (sects. Vulpia, Monachne, Spirachne, Loretia, Apalochloa) and three sections and one subsection of fine-leaved Festuca (sects. Eskia, Festuca, Aulaxyper, subsect. Exaratae) were included in the analysis. Six minor annual genera that have been considered in the past to be related either to Vulpia or to these fescues (Psilurus, Ctenopsis, Cutandia, Narduroides, Micropyrum, Wangenheimia) were also analyzed in order to estimate an evolutionary framework for this poorly known group of ephemeral or thin-leaved grasses. Single representatives of other less related groups of Poeae (Festuca subg. Schedonorus and Drymanthele, Lolium, Dactylis, Poa, Puccinellia, Sesleria). Triticeae (Secale), and Brachypodieae (Brachypodium) were also studied. Phylogenetic analyses were performed based on parsimony and Bayesian inference criteria using Brachypodium distachyon as outgroup. Our results indicate that Vulpia and the fine-leaved Festuca are, respectively, polyphyletic and paraphyletic assemblages of several taxa. A well-supported monophyletic group that encompasses the fine-leaved Festuca and Vulpia lineages as well as the other six ephemeral genera (FEVRE) has been obtained from both the separate and the combined ITS and trnL-F analyses. Within this FEVRE clade Festuca sect. Eskia is shown to be a paraphyletic assemblage basal to the other taxa; the core of the FEVRE clade contains four supported clades representing, respectively, the lineages Aulaxyper + Vulpia pro part (diploid), Festuca + Wangenheimia, Psilurus + Vulpia pro parte (polyploid), and Spirachne + Monachne + Loretia. Vulpia unilateralis (Apalochloa) constitutes a monospecific lineage with apparent but unsupported affinities to some of its potential closer relatives. Representatives of all the Vulpia sections except those belonging to typical section Vulpia join in a paraphyletic poorly supported assemblage that also includes Cutandia, Festuca plicata, and Ctenopsis. Two of the studied annual genera, Micropyrum and Narduroides, show distant evolutionary placements in the ITS and trnL-F trees. The Festuca subsect. Exaratae taxa belong to a phylogenetic lineage diverging from those of the Festuca ovina (sect. Festuca) an F. rubra (sect. Aulaxyper) fescues. Nucleotide substitution rates show significant differences between most perennial and annual lineages; stabilized selection is maintained in the slowly diverging perennial groups, whereas the rapid adaptive evolutionary processes shown by the annual taxa may have resulted in an increased rate in cladogenesis. The Mediterranean region is hypothesized as the likely place of divergence of these grass lineages.