Contrasting demographic histories revealed in two invasive populations of the dry rot fungus Serpula lacrymans

Globalization and international trade have impacted organisms around the
world leading to a considerable number of species establishing in new
geographic areas. Many organisms have taken advantage of human-made
environments, including buildings. One such species is the dry rot fungus
Serpula lacrymans, which is the most aggressive wood-decay fungus in
indoor environments in temperate regions. Using population genomic
analyses of 36 full genome sequenced isolates, we demonstrated that
European and Japanese isolates are highly divergent and the populations
split 3,000 - 19,000 generations ago, probably predating human influence.
Approximately 250 generations ago, the European population went through a
tight bottleneck, likely corresponding to the fungus colonization of the
built environment in Europe. The demographic history of these populations,
probably lead to low adaptive potential. Only two loci under selection
were identified using a Fst outlier approach, and selective sweep analyses
identified three loci with extended haplotype homozygosity. The selective
sweep analyses found signals in genes possibly related to decay of various
substrates in Japan and in genes involved DNA replication and protein
modification in Europe. Our results suggest that the dry rot fungus
independently established in indoor environments in Europe and Japan and
that invasive species can potentially establish large populations in new
habitats based on a few colonizing individuals.