Barth Julia M I, Berg Paul R, Jonsson Per R, Bonanomi Sara, Corell Hanna, Hemmer-Hansen Jakob, Jakobsen Kjetill S, Johannesson Kerstin, Jorde Per Erik, Knutsen Halvor, Moksnes Per-Olav, Star Bastiaan, Stenseth Nils Chr, Svedäng Henrik, Jentoft Sissel, André Carl
Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, Oslo, Norway.
Faculty of Medicine, Centre for Molecular Medicine Norway (NCMM), University of Oslo, Oslo, Norway.
Mol Ecol. 2017 Sep;26(17):4452-4466. doi: 10.1111/mec.14207. Epub 2017 Jul 19.
Adaptation to local conditions is a fundamental process in evolution; however, mechanisms maintaining local adaptation despite high gene flow are still poorly understood. Marine ecosystems provide a wide array of diverse habitats that frequently promote ecological adaptation even in species characterized by strong levels of gene flow. As one example, populations of the marine fish Atlantic cod (Gadus morhua) are highly connected due to immense dispersal capabilities but nevertheless show local adaptation in several key traits. By combining population genomic analyses based on 12K single nucleotide polymorphisms with larval dispersal patterns inferred using a biophysical ocean model, we show that Atlantic cod individuals residing in sheltered estuarine habitats of Scandinavian fjords mainly belong to offshore oceanic populations with considerable connectivity between these diverse ecosystems. Nevertheless, we also find evidence for discrete fjord populations that are genetically differentiated from offshore populations, indicative of local adaptation, the degree of which appears to be influenced by connectivity. Analyses of the genomic architecture reveal a significant overrepresentation of a large ~5 Mb chromosomal rearrangement in fjord cod, previously proposed to comprise genes critical for the survival at low salinities. This suggests that despite considerable connectivity with offshore populations, local adaptation to fjord environments may be enabled by suppression of recombination in the rearranged region. Our study provides new insights into the potential of local adaptation in high gene flow species within fine geographical scales and highlights the importance of genome architecture in analyses of ecological adaptation.
适应当地环境是进化中的一个基本过程；然而，尽管基因流很高，但维持局部适应性的机制仍未得到充分理解。海洋生态系统提供了各种各样的多样栖息地，即使在以高水平基因流为特征的物种中，也经常促进生态适应。例如，海洋鱼类大西洋鳕鱼（Gadus morhua）的种群由于强大的扩散能力而高度连通，但在几个关键性状上仍表现出局部适应性。通过将基于12K单核苷酸多态性的种群基因组分析与使用生物物理海洋模型推断的幼体扩散模式相结合，我们发现，生活在斯堪的纳维亚峡湾受保护河口栖息地的大西洋鳕鱼个体主要属于近海海洋种群，这些不同生态系统之间具有相当的连通性。然而，我们也发现了离散峡湾种群的证据，这些种群在基因上与近海种群不同，表明存在局部适应性，其程度似乎受到连通性的影响。基因组结构分析揭示，峡湾鳕鱼中一个约5Mb的大型染色体重排明显过度富集，此前有人提出该重排包含对低盐度生存至关重要的基因。这表明，尽管与近海种群有相当的连通性，但通过抑制重排区域的重组，可能实现对峡湾环境的局部适应。我们的研究为在精细地理尺度上高基因流物种局部适应的潜力提供了新见解，并强调了基因组结构在生态适应分析中的重要性。
