Data from: Extensive gene flow over Europe and possible speciation over Eurasia in the ectomycorrhizal basidiomycete Laccaria amethystina complex.

Biogeographic patterns and large-scale genetic structure have been little
studied in ectomycorrhizal fungi, despite the ecological and economic
importance of ectomycorrhizal symbioses. We coupled population genetics
and phylogenetic approaches to understand spatial structure in fungal
populations on a continental scale. Using 9 microsatellite markers, we
characterised gene flow among 16 populations of the widespread
ectomycorrhizal basidiomycete Laccaria amethystina over Europe (over
2900km). We also widened our scope to two additional populations from
Japan (104 km away), and compared them with European populations through
microsatellite markers and multi-locus phylogenies, using 3 nuclear genes
(NAR, G6PD and ribosomal DNA) and two mitochondrial ribosomal genes.
European L. amethystina populations displayed limited differentiation
(average FST=0.041) and very weak isolation by distance. This panmictic
European pattern may result from effective aerial dispersal of spores,
high genetic diversity in populations, and mutualistic interactions with
multiple hosts that all facilitate migration. The multi-locus phylogeny
based on nuclear genes confirmed that Japanese and European specimens were
closely related but clustered on a geographical basis. By using
microsatellite markers, we found that Japanese populations were strongly
differentiated from the European populations (FST=0.416), more than
expected by extrapolating the European pattern of isolation by distance.
Population structure analyses clearly separated the populations into two
clusters, European and Japanese clusters. We discuss the possibility of
isolation by distance in a continuous population (considering some
evidence for a ring species over the Northern Hemisphere) versus an
allopatric speciation over Eurasia, making L. amethystina a promising
model of intercontinental species for future studies.