Improving Fungal Biodiversity Knowledge Through Field Work, Fungarium Collections, and Public Datasets

Over 90% of fungal species are undescribed and tropical areas are presumed to be both highly diverse and less studied, therefore containing a large portion of fungal species awaiting discovery. In this dissertation, I first examine this presumption by reviewing literature from long-term studies of fungi in the tropics and examining data in public biodiversity repositories. Both literature review and metabarcoding studies of soils suggest the tropics are greater in diversity than non-tropical regions in general, and for certain taxonomic groups and functional guilds. Public biodiversity repositories show that fewer molecular, conservation, and alpha diversity data exist for fungi occurring in tropical versus non-tropical locations and that less data is generated from citizen scientists in tropical localities. Second, I describe the start of a long-term fungal biodiversity study in Cusuco National Park, Honduras to improve knowledge of fungal alpha diversity in this region and determine if increased fungal richness is associated with certain environmental variables such as elevation, leaf litter depth, soil density, and canopy cover. Descriptive statistics from opportunistic collections in the summers of 2019, 2022, and 2023 and an analysis of collections from standardized plots from 2022 and 2023 are provided. Overall, 466 nuclear ribosomal internal transcribed spacer (ITS) barcode sequences were generated from 993 collections from at least 11 different classes of fungi that cluster into 392 operational taxonomic units (OTUs). The high number of OTUs represented by a single sequence and the high likelihood a new DNA sequence represented a new OTU indicate we have not captured the majority of fungal diversity in Cusuco. Preliminary results from standardized plots show that fungal richness increases as soils are less compacted and decreases as leaf litter depth increases. Finally, through a combination of fieldwork and specimens preserved in herbaria and culture collections, five new species of Helotiales in the genus Chlorosplenium are described and four new species in the genus Ascocoryne are proposed. Incorporating metabarcoding of herbarium specimens in both genera has improved our understanding of the diversity and biogeography of these groups. In both cases, the estimated number of species in each genus is double the number previously described and unique morphological features are reported, such as the production of macroscopic crystals in culture in the genus Chlorosplenium. This work highlights that advances in fungal biodiversity knowledge can occur in both temperate and tropical regions by making new collections and examining collections of fungi stored in fungaria, particularly in understudied groups, like the Helotiales.