Widespread Infection of the Hair Lichen Genus Bryoria (Parmeliaceae) by a Previously Unknown Fungal Pathogen

Abstract

Bryoria Brodo & D. Hawksw. (Parmeliaceae, Ascomycota) is one of the dominant genera of hair lichens in western North America and is characteristic of high elevation conifer forest ecosystems. In areas where Bryoria is abundant, it is common to find thalli in which the thalline filaments become conglutinated, forming brittle dead zones, or “rattails”. I sampled Bryoria thalli across western Canada and the northwestern United States monitoring thallus dieback at different times of the year. I found that this dieback phenomenon is associated with the winter growth of a mold-forming basidiomycete not previously known to associate with Bryoria. Similar Bryoria die-off has been attributed to extreme rain events in British Columbia and Norway, but not in the presence of a necrotrophic mold. I report that this fungus belongs to Athelia Pers., a cosmopolitan genus of the basidiomycete family Atheliaceae containing economically significant pathogens. To place the Bryoria-associated fungi within Athelia, I designed Athelia-specific primers for two gene regions (EF1-α and ITS) and screened the mold directly along with apparently uninfected lichen specimens to assess its potential latent occurrence. The pathogen initially appeared to be related to A. epiphylla Pers. and A. acrospora Jülich, a species heretofore known only from dead wood. Based on phylogenetic placement along with its distinctly sized basidia and basidiospores, this mold is presented here as Athelia seborrheica, a new species. It was found to frequently infect members of Bryoria sect. Implexae (Gyeln.) Brodo & D. Hawksw., occasionally associates with other foliose and fruticose species within Parmeliaceae, and does not appear to exist within thalli asymptomatically. Whether or not this widespread infection of Bryoria in western North America is a recent event or simply an overlooked phenomenon is difficult to determine with certainty. This research will serve as a benchmark for documenting the pathogenic outbreak affecting an ecologically significant lichen genus.