Little to no genetic structure in the ectomycorrhizal basidiomycete Suillus spraguei (Syn. S-pictus) across parts of the northeastern USA

Population genetic studies of ectomycorrhizal fungi at scales larger than 100 km are still relatively rare with highly variable results. In this study, we determined the population genetic structure of the ectomycorrhizal basidiomycete Suillus spraguei over distances up to 600 km in northeastern USA forests. S. spraguei associates exclusively with five-needled pines and only with white pine (Pinus strobus) in the eastern USA. We used six microsatellite loci to assess the genetic structure between eight sites sampled in the Adirondack Park of New York and seven sites sampled in other forests of New York, Pennsylvania, and Massachusetts. Except for one site, little to no genetic differentiation was detected in pairwise comparisons of the sites (F (ST) = 0 to 0.05). Only one site was moderately differentiated from most other sites (F (ST) = 0.02 to 0.15). The Mantel test showed no significant correlation between genetic and geographic distances (isolation by distance; R (2) = 0.003, P = 0.3). The STRUCTURE analysis also supported the presence of a single cluster (K = 1).