Data from: Genetic evidence for the uncoupling of local aquaculture activities and a population of an invasive species – a case study of Pacific oysters (Crassostrea gigas)

Human-mediated introduction of non-native species into coastal areas via
aquaculture is one of the main pathways that can lead to biological
invasions. To develop strategies to counteract invasions it is critical to
determine whether populations establishing in the wild are self-sustaining
or based on repeated introductions. Invasions by the Pacific oyster
(Crassostrea gigas) have been associated with the growing oyster
aquaculture industry worldwide. In this study, temporal genetic
variability of farmed and wild oysters from the largest enclosed bay in
Ireland was assessed to reconstruct the recent biological history of the
feral populations using seven anonymous and seven microsatellites linked
to expressed sequence tags (ESTs). There was no evidence of EST-linked
markers showing footprints of selection. Allelic richness was higher in
feral than in aquaculture samples (p=0.003, paired t-test). Significant
deviations from Hardy-Weinberg equilibrium (HWE) due to heterozygote
deficiencies were detected for almost all loci and samples, most likely
explained by the presence of null-alleles. Relatively high genetic
differentiation was found between aquaculture and feral oysters (largest
pairwise multilocus FST 0.074, p < 0.01) and between year classes
of oysters from aquaculture (largest pairwise multilocus FST 0.073, p
< 0.01), which was also confirmed by the strong separation of
aquaculture and wild samples using Bayesian clustering approaches. A
ten-fold higher effective population size (Ne) – and a high number of
private alleles – in wild oysters suggest an established self-sustaining
feral population. The wild oyster population studied appears
demographically independent from the current aquaculture activities in the
estuary and alternative scenarios of introduction pathways are discussed.