Cryptic diversity in the Antherospora vaillantii complex on Muscari species.

The anther smut fungi in the ustilaginomycetous genus Antherospora (Floromycetaceae, Urocystidales) that infect monocots, are currently placed in nine species. Against the background of the generally observed high host specificity in smut fungi, the broad host range reported for some of the species suggests much higher diversity. Antherospora vaillantii s. lato includes anther smuts on different Muscari species. In this study, specimens of anther smuts on Muscari armeniacum, M. botryoides, M. comosum, and M. tenuiflorum were analysed by rDNA sequences and morphology to determine whether they represented one polyphagous or several host specific species. The molecular phylogeny revealed three distinct lineages that were correlated with host plants, yet had only slight morphological differences. These lineages are assigned to three cryptic species: Antherospora hortensis sp. nov. on Muscari armeniacum, A. muscari-botryoidis comb. nov. (syn. Ustilago muscari-botryoidis) on M. botryoides, and A. vaillantii s. str. on M. comosum and M. tenuiflorum. All species on Muscari form a monophyletic group within Antherospora, and the phylogenetic relations within this group coincide well with the subgeneric classification of the respective host species. This indicates a common ancestry of Muscari anther smuts and co-evolution as a driver of their diversification.

A new species of Antherospora supports the systematic placement of its host plant.

The morphology and phylogeny of anther smut specimens on Tractema verna collected in the United Kingdom were investigated using light microscopy, scanning electron microscopy and partial rDNA sequence analyses. The anther smut of Tractema verna shows similarity to Antherospora eucomis, A. scillae, A. tourneuxii, A. urgineae, A. vaillantii, and A. vindobonensis but differs in spore size range, spore wall thickness, host plant genera and considerable divergences of ITS and LSU sequences. Consequently, the smut is described here as a new species, Antherospora tractemae. The host plant was formerly included in the genus Scilla (S. verna), but recently moved to a distinct genus Tractema. Molecular phylogenetic analyses reveal that Antherospora tractemae is sister to the lineage of Muscari-parasitizing Antherospora and only distantly related to the Scilla-parasitizing Antherospora species. Thus, the phylogenetic placement of the smut fungus supports the systematic placement of its host plant.