Molecular phylogeny of North American Festuca Linnaeus (Poaceae).

Abstract

Current hypotheses of the phyletic relationships in the genus Festuca and generic segregates, as expressed in classification systems, were tested using molecular data (DNA restriction endonuclease site variation of the chloroplast and nuclear genomes). Taxa native or introduced to North America were used as exemplars for seven subgenera: Drymanthele, Subulatae, Subuliflorae, Obtusae, Schedonorus, Leucopoa sensu lato (sections Leucopoa and Breviaristatae) and Festuca; and four generic segregates: Leucopoa sensu stricto (section Leucopoa), Argillochloa, Vulpia and Lolium. Cladistic analysis of 67 shared, polymorphic chloroplast DNA restriction sites (11 endonucleases) indicated that Festuca and subgeneric taxa, as circumscribed in morphologically based classifications, are polyphyletic. Phenetic analysis of 108 polymorphic chloroplast DNA restriction sites (11 endonucleases) and nuclear ribosomal DNA restriction fragment patterns (12 endonucleases) supported the results of the cladistic analysis. Two main evolutionary lines were indicated within the genus Festuca as presently constructed. One contained the vast majority of the genus Festuca exemplars, including the subgenera Drymanthele, Subulatae, Subuliflorae, Obtusae and Festuca, as well as Vulpia, Argillochloa and subgenus Leucopoa section Breviaristatae. The other lineage included subgenus Schedonorus, subgenus Leucopoa section Leucopoa and the genus Lolium. Analyses support the recognition of four related genera in the two lineages, Vulpia and Festuca (including subgenus Leucopoa section Breviaristatae, and the subgenera Drymanthele, Subulatae, Subuliflorae, Obtusae, and Festuca) in one and Leucopoa sensu stricto (including only section Leucopoa) and Lolium (including Festuca subgenus Schedonorus) in the other, respectively. The recognition of the monotypic generic segregate Argillochloa (= Festuca dasyclada) is not supported by the analyses.