Noll et al.: Analysis of genetic structure of Asian and western Oncorhynchus gobuscha 
133 
Sea of Okhotsk Bering Sea Gulf of Alaska 
W Kamchatka 
Japan (Pacific) 
3 ■ i • i • ' i I I f I , — T \ 
0 0 01 0.02 0.03 0.04 0.05 0 06 0 07 
Genetic distance 
Figure 3 
Neighbor-joining tree based on allele frequencies at 21 loci, showing Cavalli-Sforza and 
Edwards ( 1967) chord distances among pink salmon from Japan, Russia, and Alaska. Sig- 
nificance between nodes or of collections joined at nodes were tested within basins by 
using log-likelihood ratios (G-tests; Sokal and Rohlf, 1995) of the 21 loci to test homogene- 
ity of branches joined at a node, and between basins by tests of homogeneity of the two 
adjacent branches. Jack-knifing populations to test the stability of the tree produced two 
local rearrangements that involved only the Aleutian Islands and Bristol Bay collections. 
The eastern Pacific Ocean and Bering Sea collections had the following sample sizes: Bris- 
tol Bay, n = 146; Aleutian Islands, n = 642; Norton Sound, n = 201; and Kodiak Island, n = 
66 (Gharrett et ah, 1988). 
Table 5 
Gene diversity analysis of even-year pink salmon broodlines. Relative gene diversities are estimated from the 21 -locus set common 
to collections of this study and that of Gharrett et al. ( 1988). Estimates and standard deviations are jackknife estimates based on 
the total expected heterozygosity at each level of hierarchy. 
Number of 
Source 
regions 
G st 
g sg 
G gt 
Sea of Okhotsk 
3 
0.0031 ±0.0006 
Bering Sea 
4 
0.0079 ±0.0003 
Gulf of Alaska 
2 
0.0043 ±0.0006 
Total 
9 
0.0230 ±0.0025 
0.0055 ±0.0002 
0.0175 ±0.0025 
ences among regions ( G ST ) as well as to the average varia- 
tion among regions within a basin ( G sg ) and among basins 
(G gt ) (Table 5). The diversity within areas was low, rang- 
ing from 0.31 to 0.79%, and averaging 0.55%. The diver- 
sity among areas was 1.75%, and the average within each 
stream was 98.25%. 
We also analyzed genetic variability by comparing aver- 
age expected heterozygosities (Nei, 1978). Eastern Pacific 
pink salmon populations appeared to have higher hetero- 
zygosities than western populations. With the 36-locus da- 
ta set, the average heterozygosity of the five Alaska collec- 
tions was 0.074 ±0.004 (mean ±SE) compared with 0.056 
±0.004 for 13 Asian collections. Using the 21 loci common 
to the three geographic regions shown by Figure 3, we es- 
timated heterozygosities of 0.061 ±0.002 for three regions 
within the Sea of Okhotsk, 0.073 ±0.004 for four regions 
in the Bering Sea, and 0.099 ±0.003 for the two regions in 
the Gulf of Alaska. Heterozygosities for these samples of 
allozyme loci increased from west to east. 
Discussion 
Heterogeneity among even-year pink salmon populations 
in Asian regions contrasted strongly with the relative 
homogeneity we observed within regions. For example, 
