Molecular sequence data assess the value of morphological characteristics for a phylogenetic classification of species of Cintractia

摘要

The genus Cintractia s. l. (Ustilaginales, basidiomycetes) comprises about 40 species of smut fungi infecting Cyperaceae and Juncaceae. These organisms form a phenetic continuum with respect to their sets of morphological character states, which do not allow a clear delimitation of infrageneric groups. According to sequence data of the large subunit ribosomal DNA of 17 species of Cintractia s. l. and related taxa of other genera of smut fungi, Cintractia s. l. is polyphyletic. Five groups of species shown by sequence data are characterized morphologically as different genera: Cintractia s. s., Tolyposporium, and the new genera Gymnocintractia, Leucocintractia, and Stegocintractia. Species of Cintractia s. s. and Tolyposporium form one clade, which is supported morphologically by similar soral structure. In the phylogram based on large subunit rDNA sequence data presented here, Cintractia s. s. seems to be paraphyletic, but the bootstrap values of this topology are very low and members of Cintractia s. s. and Tolyposporium are morphologically easily distinguishable by the presence of irregularly roughly warty teliospores in balls in species of Tolyposporium and single, finely warty teliospores in species of Cintractia s. s. Species of Gymnocintractia and those of Leucocintractia are sister taxa, although the former are similar to species of Stegocintractia by the absence of a sterile stroma in the sori and foveolate teliospores, and the latter to those of Cintractia s. s. by the presence of a sterile stroma, peridia, and nonfoveolate teliospores. Distinctive morphological characteristics were, however, found, such as the presence of fungal peridia in sori of species of Stegocintractia and their absence in those of species of Gymnocintractia, teliospores with rough warts forming ridges in species of Leucocintractia and finely warty ones in species of Cintractia s. s. Hosts of species of Cintractia s. s., Gymnocintractia, and Leucocintractia belong to the Cyperaceae, those of species of Stegocintractia and Tolyposporium to the Juncaceae.