The large geographic distribution of the eastern oyster, Crassostrea virginica makes it an ideal species to test how populations have adapted to latitudinal gradients in temperature. Despite inhabiting distinct thermal regimes, populations of C. virginica near the species' southern and northern geographic range show no population differences in their physiological response to temperature. In this study, we used comparative transcriptomics to understand how oysters from either end of the species' range maintain enantiostasis across three acclimation temperatures (10, 20, and 30˚C). With this approach, we identified genes that were differentially expressed in response to temperature between individuals of C. virginica collected from New Brunswick, Canada and Louisiana, USA. We observed a core set of genes whose expression responded to temperature in both populations, but also an even larger set of genes with expression patterns that were unique to each population. Intriguingly the genes with population-specific responses to temperature had elevated FST and Ka/Ks ratios compared to the genome-wide average. In contrast, genes showing only a response to temperature were found to only have elevated FST values suggesting that divergent FST may be due to selection on linked regulatory regions rather than positive selection on protein coding regions Taken together our results suggest that, despite coarse-scale physiological similarities, natural selection has shaped divergent gene expression responses to temperature in geographically separated populations of this broadly eurythermal marine invertebrate.

中文翻译：

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东部牡蛎Crassostrea virginica温度适应的转录组学特征。

东部牡蛎（Crassostrea virginica）的地理分布广泛，使其成为测试种群如何适应温度的纬度梯度的理想物种。尽管居住在不同的热态下，但该物种的南部和北部地理范围附近的维吉尼亚梭菌种群在其对温度的生理反应中没有种群差异。在这项研究中，我们使用比较转录组学方法来了解该物种范围两端的牡蛎如何在三个适应温度（10、20和30°C）下保持对映体稳定。通过这种方法，我们鉴定了从加拿大新不伦瑞克省和美国路易斯安那州收集的维吉尼亚衣原体个体对温度的响应而差异表达的基因。我们观察到一组核心基因，其表达在两个种群中均响应温度，但还观察到一组更大的基因，其表达模式对每个种群而言都是独特的。有趣的是，与全基因组范围内的平均值相比，对温度具有种群特异性响应的基因具有更高的FST和Ka / Ks比。相反，发现仅显示对温度响应的基因的FST值仅升高，这表明FST的差异可能是由于在相关调控区的选择，而不是由于蛋白质编码区的正选择。在生理上相似，自然选择已在这个广泛的无性热海洋无脊椎动物的地理上分离的种群中塑造了不同的基因表达对温度的响应。