LAUSR

Natural products can contribute to abiotic stress tolerance in plants and fungi. We hypothesize that biosynthetic gene clusters (BGCs), the genomic elements that underlie natural product biosynthesis, display structured differences along elevation gradients. We analyzed biosynthetic gene variation in natural populations of the lichen-forming fungus Umbilicaria pustulata. We collected a total of 600 individuals from Mediterranean and cold temperate climate. Population genomic analyses indicate that U. pustulata contains three clusters that are highly differentiated between Mediterranean and cold temperate populations. One entire cluster is exclusively present in cold temperate populations, and a second cluster is putatively dysfunctional in all cold temperate populations. In these two clusters the presence of consistent allele frequency differences among replicate populations/gradients suggests that selection rather than drift is driving the pattern. In the third cluster variation is fixed in all cold temperate populations due to hitchhiking. We advocate that the landscape of fungal biosynthetic genes is shaped by both positive- and hitchhiking selection. We demonstrate, for the first-time, the presence of climate-associated BGCs and BGC variations in lichen-forming fungi. While the associated secondary metabolites of the candidate clusters are presently unknown, our study paves the way for targeted discovery of natural products with ecological significance. This article is protected by copyright. All rights reserved.