Résumé
Fungi are an omnipresent and highly diverse group of organisms, making up
a significant part of eukaryotic diversity. Little is currently known
about the drivers of fungal population differentiation and subsequent
divergence of species, particularly in symbiotic, mycorrhizal fungi. Here,
we investigate the population structure and environmental adaptation in
Suillus brevipes (Peck) Kuntze, a wind-dispersed soil fungus that is
symbiotic with pine trees. We assembled and annotated the reference genome
for Su. brevipes and resequenced the whole genomes of 28 individuals from
coastal and montane sites in California. We detected two clearly
delineated coast and mountain populations with very low divergence.
Genomic divergence was restricted to few regions, including a region of
extreme divergence containing a gene encoding for a membrane Na+/H+
exchanger known for enhancing salt tolerance in plants and yeast. Our
results are consistent with a very recent split between the montane and
coastal Su. brevipes populations, with few small genomic regions under
positive selection and a pattern of dispersal and/or establishment
limitation. Furthermore, we identify a putatively adaptive gene that
motivates further functional analyses to link genotypes and phenotypes and
shed light on the genetic basis of adaptive traits.