Research Document - 2001/097

High Levels of Genetic Variation in Northern Abalone, Haliotis kamtschatkana, of British Columbia

By R. E. Withler, A. Campbell, S. Li, K. M. Miller, D. Brouwer,   B. G. Lucas 

Abstract

Northern abalone (Haliotis kamtschatkana), from 18 sites in British Columbia and one site in southeastern Alaska, were surveyed for variation at 12 polymorphic microsatellite loci. In all samples, levels of observed heterozygosity were high (Ho = 0.64-0.74) but lower than values expected (He = 0.88-0.90) under conditions of Hardy Weinberg equilibrium (HWE), due to heterozygote deficiencies at all 12 loci. Levels of excess homozygosity varied more among loci (fis = 0.02-0.55) than among samples (fis = 0.16-0.28), indicating that inbreeding alone did not account for the large homozygote excess observed at some loci. Based on the six loci at which genotypic frequencies were closest to HWE expectations, the estimated level of inbreeding in northern abalone aggregations was 0.06. The high level of He characterizing all samples resulted in a large estimated effective population size for northern abalone (420,000), consistent with a high estimate for the historical average number of migrants entering abalone aggregations each generation (~20). Hierarchical analysis of gene diversity revealed that 99.6% of genetic variation was contained within abalone samples and only 0.4% partitioned among samples. Approximately 0.2% of variation was accounted for by differentiation between abalone of the Queen Charlotte Islands and Alaska and those found in central and southern British Columbia, and the remaining 0.2% was due to differences among samples within each of those two regions. The results indicate that, historically, northern abalone aggregations did not represent isolated breeding units and any disruption of gene flow that may have been caused by recent low abundance levels cannot yet be detected in non-size-structured samples of adult abalone.

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