Abstract：
The extent to which chemical contamination affects the population structure and genetic diversity of natural populations remains elusive. Here, we used the whole-genome resequencing and transcriptome to diagnose the effects of long-term exposure to multiple elevated chemical pollutants on the population differentiation and genetic diversity in oysters Crassostrea hongkongensis in a typically polluted Pearl River Estuary (PRE) of Southern China. Population structure revealed an obvious differentiation between the PRE oysters and those collected from a nearby clean Beihai (BH) individuals, while no significant differentiation was observed among individuals collected from the three pollution sites within PRE due to the high gene flow. The decreased genetic diversity in the PRE oysters reflected the long-term effects of chemical pollutants. Selective sweeps between BH and PRE oysters revealed that chemical defensome genes, including glutathione S-transferase, zinc transporter, were responsible for their differentiation, sharing common metabolic process of other pollutants. Combined with the genome-wide association analysis, 25 regions containing 77 genes were identified to be responsible for the direct selection regions of metals. Linkage disequilibrium blocks and haplotypes within these regions provided the biomarkers of permanent effects. Our results provide important insights to the genetic mechanisms underlying the rapid evolution under chemical contamination in marine bivalves.
摘要：
化学污染对自然种群的种群结构和遗传多样性的影响程度仍然难以捉摸。这里,我们使用全基因组重测序和转录组来诊断长期暴露于多种升高的化学污染物对中国南方典型污染的珠江口（PRE）牡蛎种群分化和遗传多样性的影响。种群结构显示，PRE牡蛎与从附近干净的北海（BH）个体收集的牡蛎之间存在明显差异，而由于高基因流量，从PRE内三个污染地点收集的个体之间没有观察到明显的差异。PRE牡蛎遗传多样性的下降反映了化学污染物的长期影响。BH和PRE牡蛎之间的选择性扫描揭示了化学防御基因，包括谷胱甘肽S-转移酶,锌转运蛋白,负责他们的分化，共享其他污染物的共同代谢过程。结合全基因组关联分析，含有77个基因的25个区域被鉴定为负责金属的直接选择区域。这些区域内的连锁不平衡块和单倍型提供了永久效应的生物标志物。我们的结果为海洋双壳类动物在化学污染下快速进化的遗传机制提供了重要见解。
