Genetic Interpretation of Broad-Scale Microsatellite Polymorphism in Odd-Year Pink Salmon

We examined genetic variation at five microsatellite loci in 12 odd-year populations and one even-year population of pink salmon Oncorhynchus gorbuscha from six geographic regions of North America. The degree of polymorphism varied widely among loci. The total number of alleles in the odd-year samples varied from 4 (Oneμ3) to 53 (Ssa85). A probability test revealed significant heterogeneity in allele frequencies among all odd-year samples and among pooled odd-year samples from six regions. We compared estimates of a standard index of population structure (θ) based on variance in allele frequency with a new index suggested for microsatellites (ρST) based on variance in allele size. Our results suggest is a better estimator of intralineage (odd-year × odd-year) population structure, whereas is best suited for estimating interlineage (odd-year × even-year) population structure. The difference in performance of and for estimating intralineage and interlineage population structure suggests high migrat...