Data from: Population structure of the invasive forest pathogen Hymenoscyphus pseudoalbidus

Understanding the genetic diversity and structure of invasive pathogens in
source and introduced areas is crucial to reveal hidden biological aspects
of an organism, to reconstruct the course of invasions and to establish
effective control measures. Hymenoscyphus pseudoalbidus (anamorph: Chalara
fraxinea) is an invasive and highly destructive fungal pathogen on common
ash Fraxinus excelsior in Europe and occurs natively in east Asia. To get
insights into the dispersal mechanism and the history of invasion, we used
microsatellite markers and characterized the genetic structure and
diversity of H. pseudoalbidus populations at three spatial levels: (i) in
Europe; (ii) at the epidemic front and (iii) between Europe and Japan. The
1208 European strains form one large population as no evident structure
was detected using Bayesian and multivariate clustering analysis. Only the
distribution of genetic diversity in space, pairwise population
differentiation (GST) and the spatial analysis of principal components
revealed a faint geographic pattern around Europe. A significant allele
deficiency in most European populations pointed to a recent genetic
bottleneck whereas no pattern of isolation by distance was found.
Populations from Japan harbored a higher genetic diversity and were
genetically differentiated from European ones. Nevertheless, phylogenetic
and network analysis clearly demonstrated that individuals from both
regions are conspecific. Our data suggest that H. pseudoalbidus was
introduced only once by a minimum of two individuals. The potential source
region of H. pseudoalbidus is huge and further investigations are required
for a more accurate localization of the source population.