ABSTRACT Aspergillus fumigatusis a ubiquitous mold and a common human fungal pathogen. Recent molecular population genetic and epidemiological analyses have revealed evidence for long-distance gene flow and high genetic diversity within most local populations of A. fumigatus. However, little is known about the impact of regional landscape factors in shaping the population diversity patterns of this species. Here we sampled extensively and investigated the population structure of A. fumigatusfrom soils in the Three Parallel Rivers (TPR) region in Eastern Himalaya. This region is remote, undeveloped and sparsely populated, bordered by glaciated peaks more than 6,000 m above sea level, and contained three rivers separated by tall mountains over very short horizontal distances. A total of 358 A. fumigatusstrains from 19 sites along the three rivers were isolated and analyzed at nine loci containing short tandem repeats. Our analyses revealed that mountain barriers, elevation differences, and drainage systems all contributed low but statistically significant genetic variations to the total A. fumigatuspopulation in this region. We found abundant novel alleles and genotypes in the TPR population of A. fumigatusand significant genetic differentiation between this population and those from other parts of Yunnan and the globe. Surprisingly, despite limited human presence in this region, about 7% of the A. fumigatusisolates were resistant to at least one of the two medical triazoles commonly used for treating aspergillosis. Our results call for greater surveillance of this and other human fungal pathogens in the environment. IMPORTANCE
The extreme habitat fragmentation and substantial environmental heterogeneity in the TPR region have long known to contribute to geographically shaped genetic structure and local adaptation in several plant and animal species. However, there have been limited studies of fungi in this region.
Aspergillus fumigatusis a ubiquitous pathogen capable of long-distance dispersal and growth in diverse environments. In this study, using A. fumigatusas a model, we investigated how localized landscape features contribute to genetic variations in fungal populations. Our results revealed that elevation and drainage isolation rather than direct physical distances significantly impacted genetic exchange and diversity among the local A. fumigatuspopulations. Interestingly, within each local population, we found high allelic and genotypic diversities, and with evidence ~7% of all isolates being resistant to two medical triazoles, itraconazole and voriconazole. Given the high frequency of ARAF found in mostly natural soils of sparsely populated sites in the TPR region, close monitoring of their dynamics in nature and their effects on human health is needed.