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Currently, the monophyletic lineage of anther smuts on Caryophyllaceae includes 22 species classified in the genus Microbotryum. They are model organisms studied in many disciplines of fungal biology. A molecular phylogenetic approach was used to resolve species boundaries within the caryophyllaceous anther smuts, as species delimitation based solely on phenotypic characters was problematic. Several cryptic species were found amongst the anther smuts on Caryophyllaceae, although some morphologically distinct species were discernible, and most species were characterized by high host-specificity. In this study, anther smut specimens infecting Silene saxifraga were analysed using rDNA sequences (ITS and LSU) and morphology to resolve their specific status and to discuss their phylogenetic position within the lineage of caryophyllaceous anther smuts. The molecular phylogeny revealed that all specimens form a monophyletic lineage that is supported by the morphological trait of reticulate spores with tuberculate interspaces (observed in certain spores). This lineage cannot be attributed to any of the previously described species, and the anther smut on Silene saxifraga is described and illustrated here as a new species, Microbotryum silenes-saxifragae. This species clusters in a clade that includes Microbotryum species, which infect both closely and distantly related host plants growing in diverse ecological habitats. It appears possible that host shifts combined with changes to ecological host niches drove the evolution of Microbotryum species within this clade.

The recently described fungal phylum Entorrhizomycota was established solely for the genus Entorrhiza, species of which cause root-galls in Cyperaceae and Juncaceae. Talbotiomyces calosporus (incertae sedis) shares morphological characteristics and an ecological niche with species of Entorrhiza. We investigated the higher classification of T. calosporus to determine whether it belongs in Entorrhizomycota. Ribosomal DNA sequences showed Talbotiomyces to be a close relative of Entorrhiza and both taxa form a highly supported monophyletic group. Based on molecular phylogenetic analyses and in congruence with existing morphological and ecological data, Entorrhiza and Talbotiomyces represent a deep dichotomy within the Entorrhizomycota. While species of Entorrhiza are characterised by dolipores and occur on monocotyledons, members of Talbotiomyces are characterised by simple pores and are associated with eudicotyledons. This expands the host range of the recently described Entorrhizomycota from Poales to other angiosperms. Higher taxa, namely Talbotiomycetales ord. nov. and Talbotiomycetaceae fam. nov., are proposed here to accommodate Talbotiomyces.