HEDGECOCK ET AL.: GENETIC VARIATION IN PACIFIC SARDINES 



Laboratory where they were kept in a -70°C 

 freezer until dissection. 



Data Taken on Specimens 



Eye, heart, Uver, and skeletal muscle tissue 

 samples were taken from each of the 432 north- 

 ern anchovy used for this study. For all speci- 

 mens but those from population sample 8, stan- 

 dard length and sex were recorded and otoliths 

 were taken. Annuli were counted by one of us 

 (F. L. Sly) in a manner similar to that described 

 for the sardine, following the methods of CoUins 

 and Spratt (1969). 



The electrophoretic protocol used to separate 

 24 proteins encoded by 39 scorable genes is given 

 in Table 1. These proteins were assayed in tissue 

 samples from an average of nearly 46 specimens 

 (minimum of three) from each of the 9 population 

 samples. Genetic interpretation and allozyme 

 nomenclature were as described above for the 

 sardine analysis with the following additions: 

 1) Gels for polymorphic enzymes were scored 

 independently by the authors D. Hedgecock and 

 Gang Li, and any discrepancy between the two 

 scores was resolved by ree.xamination and nego- 

 tiation; and 2) problems with the resolution of 

 certain allozymes from Hver tissue became ap- 

 parent. A pattern of missing IDH-2, missing 

 EST-5, and blurred LDH-3 and HBDH-2 pheno- 

 types — the last mimicking the 100/105 polymor- 

 phism — was subsequently associated with de- 

 generated liver tissues in individual specimens 

 or even entire population samples that were, 

 perhaps, not frozen soon enough after trawhng. 

 IDH-2 appeared most sensitive to this and was 

 eliminated from the study, except as an indicator 

 of degenerate liver tissue. To correct for poten- 

 tial bias in Hbdh-2 data, individual HBDH-2 

 scores were omitted if (i) any other element of 

 the above composite, degenerate-liver zymo- 

 gram was observed in that individual and (ii) 

 missing elements (i.e., IDH-2 and EST-5) were 

 observed in at least one other specimen from the 

 same population sample (to prevent a missing or 

 failed enzyme assay from causing data rejec- 

 tion). Mean number of individuals assayed for 

 HBDH per population sample was thus reduced 

 to 33 ± 3. 



Allozyme Data Analysis 



Single-individual genotypes were recoded as 

 paired alphabetical characters and submitted to 

 the BIOSYS-1 program of Swofford and Selan- 



der (1981) for calculations of allelic frequencies, 

 average proportions of heterozygous individuals 

 per locus (Hq and //g as defined above), propor- 

 tions of polymorphic genes (P, where a locus is 

 considered polymorphic if the frequency of the 

 most common allele does not exceed 0.99), chi- 

 square goodness-of-fit tests to Hardy-Wein- 

 berg-Castle (H-W-C) equilibrium genotypic pro- 

 portions using Levene's (1949) correction for 

 small sample sizes, Wright's (1978) F-statistics, 

 and Nei's (1978) unbiased estimates of average 

 genetic identity (/) and genetic distance (D). 

 Averaging of P and H over population samples 

 was done using angular transformation followed 

 by back-transformation of means and confidence 

 limits. Spearman rank correlations of angular- 

 transformed allelic frequencies with the sines of 

 latitude of collection localities, log-likelihood 

 ratio (G) tests of the independence of allelic fre- 

 quency and locality, and analyses of allehc fre- 

 quencies cross-classified by locahty, sex, and age 

 (ACCCD; Fienberg 1980) were used to evaluate 

 sources of genetic heterogeneity. 



RESULTS 



Sardinops sagax caerulea 



Genetic Variation 



We detected electrophoretic variation in the 

 zymograms of seven proteins, including three 

 di- and tripeptidases, from Pacific sardines, 

 (EST-6, FBP, GPDH, IDH-2, LGG, LT, PP, 

 6PGDH, SOD; Table 2B). There is, however, 

 remarkably little protein polymorphism and indi- 

 vidual heterozygosity at the total 32 loci ex- 

 amined in 149 Pacific sardines (Table 2A). The 

 proportion of polymorphic genes ranges from 

 7.4^??^ in each of the samples from Tomales and 

 Magdalena Bays to 26.9% in the Guaymas 

 sample, with an average of 12.3% (95% C.L.: 

 6.4-19.6%). Average heterozygosities range 

 from 0.5% in the Magdalena Bay sample to 1.7% 

 in the Guaymas sample, with a mean over all 

 population samples of 1.0% (95% C.L.: 0.6- 

 1.5%). Estimates of genetic variation are prob- 

 ably best for the Guaymas sample, for two 

 reasons: 1) There were generally larger num- 

 bers of individuals sampled per gene, which ac- 

 counts for the finding of rare heterozygotes at 

 Idh-2, Lgg, and Pp, loci that were not well 

 sampled elsewhere. 2) We sampled two moder- 

 ately polymorphic loci, Est-6 and Fbp, that were 

 not scored in any other large population sample. 

 There are no significant diffei'ences between 



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