Heterozygosity and morphological variability of pink salmon (Oncorhynchus gorbuscha) from southern British Columbia and Puget Sound

Abstract

We compared variability in gill raker number and four morphometric characters with heterozygosity at enzymatic loci within and among populations of pink salmon (Oncorhynchus gorbuscha) in southern British Columbia and Puget Sound. Among individuals, there was no relationship between levels of heterozygosity at eight electrophoretic loci and degree of meristic or morphometric variation. Decreased phenotypic variance was not associated with increased heterozygosity. Among populations of pink salmon, increased levels of average heterozygosity were not associated with decreased phenotypic variation. Our results do not support the hypothesis that more heterozygous individuals are less phenotypically variable than more homozygous ones as a result of genetic homeostasis and a canalisation of morphology during development. Genetic distances between pairs of pink populations were significantly correlated with pairwise Mahalanobis distances derived from meristic characters (gill rakers) and less strongly correlated with distances derived from morphometric characters. Pink salmon are morphometrically adapted to the natal stream environment, whereas biochemical and meristic characters in these populations may be less affected differentially by local selective forces.Key words: salmon, electromorphs, homeostasis, genetic variability, heterozygosity.