Spatial analysis of within-population microsatellite variability reveals restricted gene flow in the Pacific golden chanterelle (Cantharellus formosus)

Abstract

We examined the within-population genetic structure of the Pacific golden chanterelle (Cantharellus formosus) in a 50 y old forest stand dominated by Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) with spatial autocorrelation analysis. We tested the null hypothesis that multilocus genotypes possessed by chanterelle genets were randomly distributed within the study area. Fruit bodies from 203 C. formosus genets were collected from a 50 ha study plot. One hundred six unique multilocus genotypes were identified after scoring these collections at five microsatellite loci. Statistically significant positive spatial autocorrelation was detected indicating the presence of fine-scale genetic structure within the area. Repeated autocorrelation analyses with varied minimum distance classes (50–500 m) detected positive spatial genetic structure up to 400 m. Therefore nonrandom evolutionary processes (e.g., isolation by distance) can cause fine-scale genetic structure in C. formosus. The implications of this research for future broad-scale population studies of this species are that population samples should be separated by at least 400 m to be considered statistically independent. Sampling designs that account for fine-scale genetic structure will better characterize heterogeneity distributed across the landscape by avoiding the effects of pseudo replication.

• correlogram
• Ectomycorrhizal
• fungi
• genetic structure
• spatial autocorrelation

The authors thank Jason Dunham and Annette Kretzer for many useful discussions regarding sampling design, Dylan Nelson for countless DNA extractions, Dave Pilz for identification of the study area and Caprice Rosato for running many genescan gels on short notice. Joey Spatafora and Mike Blouin provided laboratory resources, and Mike Taft and Teresa Lebel were indispensable during field sampling and laboratory processing of samples. Kelly Collins kindly provided data that aided in genet resolution. This manuscript greatly benefited from comments made by David Geiser and two anonymous reviewers. Our research was financed by cooperative agreement PNW 97-5090-2-CA between the USDA Forest Service and Oregon State University.