Fungal communities of West African ectomycorrhizal woodlands

Sammanfattning: Ectomycorrhizal symbiosis is a widespread mutualist relationship between fungi and plants, often trees. It is most well-known in temperate and boreal forests, but also occurs in a variety of tropical ecosystems, including Sudanian savanna woodlands and gallery forests in West Africa. In addition to their important role in nutrient cycling, many ectomycorrhizal fungi also produce edible mushrooms as their fruit-bodies. In this thesis, I explore spatial patterns of above-ground and below-ground diversity in West African ectomycorrhizal communities, as well as the use of wild edible fungi by the local human population. In Papers I and II, I used soil DNA metabarcoding to investigate fungal communities in their vegetative state. Paper I used measurements of the scale of spatial autocorrelation within the fungal community in Sudanian woodlands in Benin as a test to compare different high-throughput DNA sequencing strategies, including short (≈350 bp) amplicon barcoding using the Illumina, Ion Torrent, and PacBio sequencing platforms, as well as long (≈1550 bp) amplicon barcoding using PacBio. There were some differences in species richness and community composition recovered by the two amplicon lengths, attributable to known primer biases for the short amplicons, but these did not lead to different ecological results. Additionally, Paper I introduced new software packages for analysis of long-amplicon metabarcoding data and integrating phylogenetic information into sequence-based taxonomic identification. In Paper II we sampled both Sudanian woodland and gallery forest sites in five countries across West Africa using long-amplicon metabarcoding with PacBio. We found significant differences in fungal community composition between Sudanian woodland and gallery forest sites, but not between different tree species within each vegetation type. Papers III and IV focused above-ground to study the natural production and human use of the mushrooms themselves. In Paper III we exhaustively collected mushrooms from nine Sudanian woodland plots in Benin during three consecutive rainy seasons. We measured the total biomass produced of each morphospecies, as well as environmental variables related to microclimate, host tree availability, and soil chemistry. Mushroom production and diversity were negatively correlated with soil nitrogen levels, and positively correlated with soil phosphorus levels. Although there were no clear differences in the fungal communities associated with the four host trees present in our plots, greater host tree diversity was associated with greater fungal diversity and productivity. Finally, Paper IV combined interviews with local people from four ethnic groups in five villages near the study sites from Paper III about their knowledge and preferences for edible mushrooms with DNA barcoding of specimens. Knowledge and preferences for different mushrooms varied between ethnic groups, but people living in a village where their ethnic group is a minority tended to absorb knowledge about mushrooms from the majority group in the village. Women over age 35 were the most knowledgeable about mushrooms, but the degree of gender difference varied between groups. We compiled a list of the most choice edible mushrooms in the area, which can inform the possibility for commercial trade in wild mushrooms to supplement the income of rural people and encourage sustainable forest management.