Multilocus heterozygosity and sexual selection in a natural population of the marine snail littorina mariae (Gastropoda: Prosobranchia)

Abstract

A positive relationship between heterozygosity and growth rate, or less frequently, between heterozygosity and fitness components, has been found in many species. A particularly important component of net fitness is sexual selection. However, no studies have been made of the relationship between this character and multilocus heterozygosity in natural populations. In this study, a natural population of the intertidal flat periwinkle Littorina mariae was used to investigate the heterozygosity-sexual fitness relationship. A positive heterozygosity-sexual fitness relationship was found in male L. mariae, but not in females. The selective coefficients acting on the different heterozygosity classes of males ranged between 0.21 and 0.57 (average 0.39), and are similar to those found in previous studies on correlations between heterozygosity and other fitness components. This relationship accounted for approximately 1 per cent of the variance in matings. Furthermore, the contribution of each locus was associated with its homozygosity excess across loci. The positive heterozygosity-sexual fitness relationship showed the same characteristics as the heterozygosity-growth rate correlation. Finally, relationships between sexual selection and size of snail, and heterozygosity and size were found, although they did not account for the heterozygosity-sexual selection relationship. © 1995 The Genetical Society of Great Britain.