Host specificity in the fungal plant parasite Anthracoidea sempervirentis (Anthracoideaceae, Ustilaginales) reveals three new species and indicates a potential split in the host plant Carex sempervirens.

The smut fungal genus Anthracoidea contains more than 100 species that parasitize hosts predominantly in the sedge genus Carex. Anthracoidea species are mainly found in the boreal zones of the Northern Hemisphere and many species have an arctic-alpine distribution. Recent re-organization of the taxonomy of the main host genus Carex questions current understanding of host associations in Anthracoidea. Host specificity for many of the species in this genus is considered to be quite broad and a host spectrum of over 10 host species is common. One aim of the study is to understand the potential influence that host taxonomy has on the evolutionary patterns of Anthracoidea. Additionally, by including more specimens, we clarify host specificity and species delimitation in Anthracoidea sempervirentis, a prevalent species occurring on different host species in different Carex subgroups using molecular data. Host colonization patterns within Anthracoidea are complex, and different subclades of Carex have been colonized several times independently, whereas clades of related Anthracoidea species often occur on Carex species from the same host clade. Parasites previously thought to be Anthracoidea sempervirentis occurring on the different Carex host are shown to be at least four distinct species that are restricted to individual host species. Three new species, Anthracoidea ferrugineae on Carex ferruginea from the Alps and the Carpathians, A. firmae on Carex firma from the Alps, and A. kitaibelianae on Carex kitaibeliana from mountains in the Balkan Peninsula, are described and illustrated. An emended description of Anthracoidea sempervirentis is also provided. Anthracoidea sempervirentis in its emended circumscription consists of two clades that correspond to respective clades within Carex sempervirens. The study shows that host colonization in Anthracoidea is more complex than current host taxonomy suggests. Further, including several specimens per host species results in a much higher diversity within Anthracoidea than previously assumed. [ABSTRACT FROM AUTHOR]