Gall et aL: Geographic variation in population genetics of Oncorhynchus tshawytscha 



Analyses 



Genetic variability for each collection of salmon was 

 assessed by calculating the frequencies of alleles at each 

 locus and average heterozygosity assuming Hardy- 

 Weinberg proportions (Nei 1973). A locus was con- 

 sidered variable if we observed polymorphism in at 

 least one sample. Analyses were based on a maximum 

 of 78 loci. If a sample was not scored for a particular 

 locus, the locus was retained for analyses involving 

 multiple samples. Deviations from expected Hardy- 

 Weinberg genotypic proportions were tested by chi- 

 square goodness-of-fit tests (Sokal and Rohlf 1981). 

 Variant allele frequencies were pooled so the expected 

 number of genotypes in a given class was always five 

 or greater. Some loci could not be tested for goodness- 

 of-fit because pooling allele frequencies to achieve a 

 minimum class-size reduced the degrees of freedom to 

 zero. In addition, the loci, PGM-3 and PGM-4, were ex- 

 cluded from goodness-of-fit tests due to the arbitrary 



nature of assigning variation to a specific locus. GPI-H, 

 LDH-1, and MDHP-2 were excluded because of the 

 method of calculating allele frequencies from the fre- 

 quency of the alternate homozygotes. 



Genetic identities (I) were calculated for each pair of 

 samples (Nei 1972) and a dendrogram was constructed 

 from estimates of I using the unweighted pair-group 

 method (UPGMA) (Sneath and Sokal 1973). Total gene 

 diversity (Hx) was partitioned to estimate within- 

 sample (Hs) and between-sample (Dgx) components, 

 and to estimate relative gene diversity (Ggx = Dgx/Hx) 

 (Nei 1973, Chakraborty and Leimar 1987). Total gene 

 diversity was partitioned into three hierarchical levels: 

 panmixia (T), area or drainage (D), and sample (S) based 

 on a priori geographic considerations (Table 1). 



An estimate of average gene flow was calculated 

 from Wright's (1943) fixation index 



FsT = l/(4Nm + 1) 



(1) 



