Asymmetric gene flow and the evolutionary maintenance of genetic diversity in small, peripheral Atlantic salmon populations

摘要: Small populations may be expected to harbour less genetic variation than large populations, but the relation between census size (N), effective population (Ne), and diversity is not well understood. We compared microsatellite in four small peripheral Atlantic salmon from Iberian peninsula three larger Scotland test whether was related size. also examined historical decline of one over a 50-year period using archival scales order marked reduction abundance accompanied by decrease diversity. Estimates (Ne) calculated temporal methods were consistently low ranging 12 31 individuals per generation considering migration, 38 175 if they regarded as closed populations. Corresponding Ne/N ratios varied 0.02 0.04 assuming migration (mean=0.03) 0.18 (mean=0.10) Population bottlenecks, inferred excess heterozygosity allelic diversity, detected all particularly those year classes derived smaller number returning adults. However, despite their declining status, continue display relatively high levels richness, similar found Scottish Furthermore, R. Ason no evidence for loss during last five decades. Thus, our results point two familiar paradigms salmonid conservation: (1)␣endangered can maintain size, (2) declines necessarily result significant Although there are several explanations such results, data physical tagging suggest that dispersal asymmetric gene flow have probably helped these thus avoid negative consequences inbreeding.