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Species Diversity, Ecology and Laccase Gene Diversity of Saprotrophic Fungi Across Different Plant Community Types


This dissertation explores the diversity, ecology and functional diversity of saprotrophic fungal across different plant community types. Saprotrophic fungi are responsible for recycling the majority of carbon from dead organic matter and have the unique ability to break down and release nutrients that can then be readily available for other organisms. A number of different biotic and abiotic factors affect the structure of saprotrophic fungal communities. Here, we investigated the effects of nutrient addition, substrate availability, and dominant plant community type on the structure and diversity of saprotrophic fungal communities. In addition, we investigated the diversity and structure of functional diversity of saprotrophic fungal communities.

The first chapter explores saprotrophic fungal diversity found in leaf litter in a diverse lowland tropical forest. We investigated the affect of nutrient addition on the saptrotrophic fungal community using a replicated factorial N, P, K, micronutrient fertilization experiment. We found that the control plots had the lowest alpha diversity compared to treatments that received fertilization. The long-term addition of nutrients increased species richness relative to controls and had an effect on taxonomic composition of the leaf litter fungal communities at lower taxonomic levels, but not at higher taxonomic levels.

The second chapter characterizes saprotrophic fungal communities on straw and wood substrates across forest and grassland plant community types and characterized how these communities changed over time as substrate quality changed. The goal was to determine if substrate, space, time or plant community were the major determinants of fungal saprotrophic community composition. We found that the wood substrates collected in the grassland and forest had the highest richness, estimated richness and phylogenetic diversity. Overall, there was a decrease in richness on the substrates in both plant communities over time, and plant community type appears to have a greater influence on saprotrophic fungal community structure than substrate type or substrate quality.

In the third chapter, we investigated the diversity of saprotrophic basidiomycete laccase genes in grassland and forest plant community types and on straw and wood substrates. Functional diversity was assessed by the functional gene encoding laccase. Laccases play an important role in soil organic matter turnover and are able to completely degrade lignin. We found that the wood substrates had significantly higher richness of estimated OTUs as compared to the straw substrates. Laccase gene diversity was compared to basidiomycete diversity. We also found that both the laccase genes and basidiomycete assemblages associated strongly with plant community type.

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