LB 30-255 - The population structure and local adaptation of an endemic Californian fungus

Dispersal limitations and geographic barriers can influence microbial population structure and gene flow at the landscape level, resulting in divergent genotypes and regional endemism. However, the drivers and genetic basis of population differentiation across large spatial scales, particularly among mycorrhizal fungi, remains poorly understood. In this study, we investigate the population structure of Suillus pungens, an ectomycorrhizal fungus endemic to the coast of California and a host-specialist to Pinus muricata and Pinus radiata. We performed whole-genome sequencing on 70 individuals collected across a latitudinal gradient, ranging from the Channel Islands in Southern California to Humboldt County in Northern California. Using analysis of single nucleotide polymorphisms, we found strong signals of population differentiation across landscapes and identified geographic features that have influenced the distribution and structure of our population. We identified dozens of putative loci under selection, and downstream analyses will provide insights into the functions of these gene regions implicated in local adaption. Our study provides evidence for strong population structure in Suillus pungens, and identifies the genetic basis of ecological adaptation to environmental gradients.