Hidden treasures of herbaria – even small collections contain a wealth of diversity: the powdery mildews of the North Carolina State Larry F. Grand Mycological Herbarium

Summary

Scientists examined preserved powdery mildew samples stored in a university herbarium and discovered four previously unknown fungal species using DNA analysis. The study shows that even small museum collections contain valuable hidden biodiversity that cannot be discovered through visual examination alone. This research highlights why it is important to preserve and maintain herbarium collections rather than discard them due to space or funding constraints, as they serve as crucial resources for understanding fungal diversity and disease.

Background

Herbaria serve as critical infrastructure for biodiversity research and species identification. Small herbarium collections, despite their size, can contain significant fungal diversity and represent underutilized resources for understanding fungal evolution and biodiversity. The Larry F. Grand Mycological Herbarium at North Carolina State University houses approximately 14,000 specimens including ~300 powdery mildew specimens.

Objective

This study assessed fungal diversity within the Larry F. Grand Mycological Herbarium with focus on powdery mildew fungi (Erysiphaceae) to determine the number of phylogenetic species compared to morphological identifications and identify undescribed species. The research aimed to demonstrate the critical role of herbarium collections in uncovering fungal biodiversity through molecular analysis of preserved specimens.

Results

Successful DNA extraction and sequencing was achieved for 220 specimens (73% success rate) representing 60 species in 10 genera from 134 host plant species. Approximately 83% of sequenced specimens had incorrect or outdated identifications based on current phylogenetic concepts. Four new species were described: Erysiphe amphicarpaeicola, E. ulmi-alatae, E. quercus-virginianae, and Takamatsuella grandii, with additional undescribed species likely present.

Conclusion

The discovery of four undescribed powdery mildew species demonstrates the urgent need to preserve herbarium collections as they represent irreplaceable scientific resources for documenting fungal biodiversity. The study emphasizes that even small, well-maintained collections contain substantial undiscovered diversity, particularly through molecular analysis of preserved specimens. Digitization alone is insufficient for cryptic species discovery, highlighting the critical importance of maintaining physical herbaria collections.
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