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.通过水产养殖将外来物种人为引入沿海区域，是引发生物入侵的主要途径之一。为制定应对生物入侵的防控策略，明确野外定殖种群究竟是可自我维持，还是依赖持续重复引入的种群，至关重要。太平洋牡蛎（Crassostrea gigas）的入侵与全球范围内不断发展的牡蛎水产养殖业密切相关。本研究以爱尔兰最大的封闭海湾的养殖与野生牡蛎为研究对象，采用7个匿名位点与7个与表达序列标签（EST）连锁的微卫星（microsatellite）标记，对其遗传变异的时间动态进行评估，以此重建野生种群的近期生物学历史。本研究未发现EST连锁标记存在选择印记的相关证据。野生种群的等位基因丰富度显著高于养殖种群（配对t检验，p=0.003）。几乎所有位点与样本均检测到因杂合子缺失导致的哈迪-温伯格平衡（Hardy-Weinberg equilibrium, HWE）显著偏离，该现象极有可能由无效等位基因（null-allele）的存在所导致。养殖与野生牡蛎种群间以及养殖牡蛎不同年组间均呈现较高的遗传分化：养殖与野生种群间的最大成对多位点FST为0.074（p<0.01），养殖牡蛎年组间的最大成对多位点FST为0.073（p<0.01）；贝叶斯聚类分析结果也显示养殖与野生样本呈现显著分离，进一步验证了这一结论。野生牡蛎的有效种群大小（effective population size, Ne）较养殖种群高出一个数量级，且拥有大量私有等位基因，这表明该区域已形成可自我维持的野生种群。本研究中的野生牡蛎种群在种群动态上似乎与当前河口区域的水产养殖活动相互独立，本文同时探讨了其他可能的物种引入途径。