Variation patterns of bilateral characters: variation among characters and among populations in the White Sea herring, Clupea pallasi marisalbi (Berg) (Clupeidae, Teleosti)

Abstract

Phenotypic variation in two populations of the White Sea herring Clupea pallasi marisalbi (Berg) (spring spawners and summer spawners), based on 21 meristic and 21 morphometric bilateral characters, has been studied. Total phenotypic variance was partitioned into a within-individual or stochastic component (fluctuating asymmetry) and an among-individual or factorial component, reflecting heterogeneity among individuals and resulting from the diversity of genotypes and environments. Both standardized stochastic and factorial components show clear negative correlations with means across characters. Negative correlation of the factorial components with means is in contradiction to the commonly accepted explanation of negative means-standardized variances association. Slopes of regression of standardized stochastic variances on means in meristic characters was significantly higher in summer spawners than in spring spawners, and results in discordance of stochastic variance across characters: it is higher in spring spawners for low and average variability characters and does not differ for both populations for high variability characters. The populations do not show notable differences in variation of morphometric characters. Consideration of other available data on these populations, such as spawning behaviour and salinity resistance of larvae, suggests that the lower slope of regression of stochastic variances on means is associated with the reduced viability of spring spawners.