Species distribution, phylogenetic structure and functional roles of detritus inhabiting fungi across contrasting aquatic environments
Freshwater fungi play a key role in plant debris decomposition, are pivotal in transferring energy and nutrients to higher trophic levels, and are essential for removing toxic heavy metals and degrading xenobiotics. In light of global climate change, habitat loss, and water pollution, it has become increasingly important to examine this understudied group of fungi. Using both culture-dependent and culture-independent techniques, I examined how habitat, geography, and phylogeny influence the structure of detritus-inhabiting fungal communities within temperate peatland and alkaline stream habitats. In addition, this research utilized traditional agar-based assays, fluorometric assays, and sequence-based methods to: 1) link community function to individual species/isolates, 2) determine functionally redundancy at the class and isolate level, 3) determine the functional magnitude of individual isolates and 4) determine if function and functional magnitude are pH-dependent. Samples of fine submerged detritus or substrate on or beneath the stream bed from six sites, four in Pennsylvania and two in Wisconsin, were collected in May, July/August, and November in 2014 for two sites and 2016 for four sites. Culture-independent analyses were conducted on 42 environmental samples collected in November 2016. Statistical analyses were conducted at the community and class level for the nine dominant fungal classes within these habitats. Functional roles were assigned using FUNGuild, agar-based assays and fluorescence assays. Alpha-diversity results indicated that stream habitats were more species rich, both in number of species and phylogenetic diversity, as compared to peatland habitats and beta-diversity analyses indicted that peatland communities were distinct from stream communities suggesting local variation and habitat as the main factors. Phylogenetic clustering within the major Ascomycota and Basidiomycota classes were prevalent within peatland habitats, while, phylogenetic clustering was more prevalent within the Mortierellomycota for stream habitats. Functional analysis indicated that many isolates are functionally redundant but that the magnitude of function varies, even between closely related isolates. Dothideomycetes isolates appeared to be more sensitive to environmental pH change as compared to Sordariomycetes isolates. The inability to assign functional roles to the majority (50%-95%) of OTUs within the nine major fungal classes highlights a huge knowledge gap in our understanding of what fungi are doing within these habitats. Lastly, two new species, Coniella lustricola and Hongkongmyces snookiorum, were isolated and described. Coniella lustricola will be a valuable comparison to pathogenic Coniella species and the discovery of Hongkongmyces snookiorum connected the asexual state with the sexual state.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign