RELATIONSHIP BETWEEN MULTIPLE-LOCUS HETEROZYGOSITY AND GROWTH RATE IN OSTREA EDULIS POPULATIONS

Relationships between multilocus heterozygosity at allozyme loci and shell length were analysed in 1-year-old cohorts of Ostrea edulis (five populations, seven loci). In contrast with usual observations for marine bivalves, as well as previous studies on captive O. edulis, our results show: (i) a lack of significant heterozygote deficiency within populations and no differentiation in allele frequences among populations; (ii) no association between multilocus heterozygosity and size, although the statistical power is sufficient to detect regressions that explain as little as 5% variance in size. The lack of repeatability of multilocus heterozygosity-fitness correlations across species or across populations within one species has already been observed, and suggested to depend on the age of the sampled cohorts. However, variation in the breeding structure of the samples can also play a role. According to the `inbreeding' hypothesis for multilocus heterozygosity-fitness correlations, populations with very low inbreeding should lack both heterozygote deficiencies and multilocus heterozygosity-fitness correlations, consistent with the present results in oysters.