Effects of land use on the fungal spore richness in small crater-lake basins of western Uganda

Mycological tools to estimate the effects of diverse land-use practices on fungal diversity are scarce, because of poor knowledge of the taxonomic diversity of tropical fungi and their response to anthropogenic habitat change. Here, we investigate assemblages of fungal spores, recently deposited in the bottom sediments of 24 small crater lakes in western Uganda, to assess the relationship between the local richness of fungi and environmental variation in the crater basin along regional gradients of natural vegetation and land use. We recovered similar to 9500 fungal spore specimens, which could be attributed to 216 morphotypes. Using an information-theoretic approach based on the corrected Akaike Information Criterion (AICc), we determined the environmental factors which best explained variation in the diversity of fungal spores among three datasets: (i) the full set of 24 crater basins, (ii) the subset of 22 basins with freshwater lakes, and (iii) the subset of 17 basins partly or completely in agricultural use (cropland, fallow land, pasture and plantation). In these 17 human-impacted crater basins our results revealed a negative relationship between fungal spore richness and the areal fraction of basins in agricultural use. However, this detrimental effect of land use on fungal spore richness was not apparent across the full set of both disturbed and (presently) undisturbed basins. This was due to large variation in fungal spore richness among the undisturbed basins covered either with forest or savannah vegetation, probably resulting from site-specific controls on fungal habitat diversity, such as climatic moisture balance and the composition of natural and/or secondary vegetation. The land-use effects on fungal spore diversity, as documented in this study, suggest that communities of tropical fungi progressively exposed to land-use practices are threatened by species loss. Hence, our study demonstrates the need to develop conservation strategies mitigating the impacts of agriculture on the biodiversity of tropical fungi.