Inbreeding involves the mating of closely related individuals at a higher frequency than at random; this can decrease the average fitness of populations and individuals by reducing the presence of heterozygotes and augmenting the expression of deleterious genes. Since marine invertebrates exhibit widespread dispersal, their potential for inbreeding is often disregarded. The adult sessile state of barnacles creates the potential for inbreeding as a result of necessary copulation between neighboring individuals. Depending on the degree of mixing that occurs during dispersal, closely related individuals or siblings may settle in close proximity, generating the possibility of kin aggregation and consequent inbreeding. Despite the high probability of closely related or sibling barnacles to settle contiguously, their genetic relatedness and potential for inbreeding remain relatively understudied. We examined genetic relatedness between individuals of Tetraclita rubescens at Monterey and Bodega Bay to elucidate the potential for nonrandom dispersal and subsequent inbreeding. Genetic relatedness was assessed through microsatellite analysis, and correlated with geographic distance, and size. There was a significant association between geographic distance and genetic relatedness at Bodega Bay, which may be attributed to lower densities of individuals, frequency of settlement events and oceanographic conditions. The results of this study demonstrate high genetic relatedness at small spatial scales, bolstering the potential for nonrandom dispersal and subsequent inbreeding of T. rubescens.

Inbreeding involves the mating of closely related individuals at a higher frequency than at random; this can decrease the average fitness of populations and individuals by reducing the presence of heterozygotes and augmenting the expression of deleterious genes. Since marine invertebrates exhibit widespread dispersal, their potential for inbreeding is often disregarded. The adult sessile state of barnacles creates the potential for inbreeding as a result of necessary copulation between neighboring individuals. Depending on the degree of mixing that occurs during dispersal, closely related individuals or siblings may settle in close proximity, generating the possibility of kin aggregation and consequent inbreeding. Despite the high probability of closely related or sibling barnacles to settle contiguously, their genetic relatedness and potential for inbreeding remain relatively understudied. We examined genetic relatedness between individuals of Tetraclita rubescens at Monterey and Bodega Bay to elucidate the potential for nonrandom dispersal and subsequent inbreeding. Genetic relatedness was assessed through microsatellite analysis, and correlated with geographic distance, and size. There was a significant association between geographic distance and genetic relatedness at Bodega Bay, which may be attributed to lower densities of individuals, frequency of settlement events and oceanographic conditions. The results of this study demonstrate high genetic relatedness at small spatial scales, bolstering the potential for nonrandom dispersal and subsequent inbreeding of T. rubescens.