Relationships between heterozygosity, allelic distance (d2), and reproductive traits in chinook salmon,Oncorhynchus tshawytscha

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Abstract
Correlations of various measures of individual genetic variation with fitness have been reported in a number of taxa; however, the genetic nature of such correlations remains uncertain. To explore this, we mated 100 male and 100 female chinook salmon (Oncorhynchus tshawytscha) in a one-to-one breeding design and quantified reproductive fitness and allocation (male gonadosomatic index, GSI; female fecundity; egg size; egg survival). Each fish was scored for allele size at seven microsatellite loci. We applied univariate and multivariate regression models incorporating two genetic variation statistics (microsatellite heterozygosity and squared allelic distance, d2) with reproductive parameters. The majority of the relationships were found to be nonsignificant; however, we found significant, positive, univariate relationships for fecundity and GSI (25% of tests) and significant, multivariate relationships at individual loci for all four traits (13% of tests). One microsatellite locus, Omy207, appeared to be closely associated with reproductive fitness in female chinook salmon (but not male), based on the multivariate analysis. Although direct tests for overdominance versus inbreeding effects proved inconclusive, our data are consistent with the presence of both inbreeding (general) and overdominance (local) effects on reproductive traits in chinook salmon.