Abstract
INTRODUCTION: Bryophyte herbarium material often contains inadvertently collected bryophilous fungi preserved with their host plant tissues, providing snapshots of the biotic aspects of bryophyte ecology in space and time. During an ongoing project to study bryophilous fungi on leafy liverworts in the genus Gymnomitrion, new records of the bryophilous ascomycete Bryobroma gymnomitrii (≡ Bryomyces gymnomitrii) were discovered in herbarium material from areas in which the fungus was previously unknown. While many host vouchers were screened, the fungus was observed in only five collections. Using B. gymnomitrii as a case study, some of the advantages and limitations associated with the utility of bryophyte collections for bryo-mycological analyses are considered. METHODS: More than 400 herbarium specimens from across Europe and North America were screened for the presence of fungi by different researchers at the following four herbaria: ALA, BBSUK, NMW and OSC. KEY RESULTS AND CONCLUSIONS: Bryobroma gymnomitrii appears to be specific to Gymnomitrion concinnatum and G. corallioides, forming gregarious, black perithecioid fruitbodies on the lower parts of host shoots. The study expands the known distribution of the fungus from a stronghold in northern and northeastern Europe to include the Aleutian Islands in Alaska. One of the host bryophytes, G. corallioides, is threatened by deterioration of its high-altitude Arctic-montane habitats, especially along the southern parts of its range, including Britain and Ireland. Our work supports the concept that research utilising herbarium material may provide valuable, unexpected outcomes, with bryophytes as important sources of fungi that have been inadvertently collected in the past.