Hirase Shotaro, Nagano Atsushi J, Nohara Kenji, Kikuchi Kiyoshi, Kokita Tomoyuki
Fisheries Laboratory, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Hamamatsu, Shizuoka, Japan.
Faculty of Agriculture, Ryukoku University, Otsu, Shiga, Japan.
Mol Ecol. 2025 Jan;34(2):e17599. doi: 10.1111/mec.17599. Epub 2024 Dec 16.
In the marine realm, unidirectional ocean currents often lead to high migration rates of marine organisms and, therefore, inhibit the formation of their latitudinal genetic structure. In contrast, cryptic latitudinal structures associated with local adaptation may frequently exist in widespread species generally exposed to a strong environmental heterogeneity. However, our understanding of the evolvability of locally adapted populations in open marine environments still needs to be completed. The coastal area along the Sea of Japan, where the Tsushima Warm Current flows from south to north in the Japanese Archipelago, provides a good model system for exploring this question. This study explored evidence for latitudinal local adaptation along with the prevailing ocean current in the ice goby Leucopsarion petersii at the phenotypic and genomic levels. Common garden experiments clearly showed genetically based clinal variation in growth rate, strongly suggesting local adaptation through conutergradient selection of this fitness-related trait. Analyses based on reduced-representation sequencing revealed a slight signal of genetic differentiation between the southern and northern populations, although continuous historical gene flow between them was supported by demographic modelling. Also, whole-genome resequencing showed their independent demographic history during the last glacial period. Thus, these results suggest that gene flow along with the prevailing ocean current is somewhat limited, and the populations are not completely panmictic. Furthermore, the selection scan based on low-coverage genome-wide sequencing detected putative genomic signatures of latitudinal adaptation of growth-related genes. Thus, our integrative study provided a novel example of marine local adaptation under a large ocean current.
在海洋领域，单向洋流常常导致海洋生物的高迁移率，因此抑制了它们纬度遗传结构的形成。相比之下，与局部适应相关的隐性纬度结构可能经常存在于普遍面临强烈环境异质性的广泛分布物种中。然而，我们对开阔海洋环境中局部适应种群的进化能力的理解仍有待完善。日本海沿岸地区，对马暖流在日本列岛由南向北流动，为探索这个问题提供了一个很好的模型系统。本研究在表型和基因组水平上探索了冰鰕虎鱼（Leucopsarion petersii）沿盛行洋流的纬度局部适应证据。共同花园实验清楚地表明了生长率基于遗传的渐变变异，强烈暗示了通过对这种与适应性相关性状的反梯度选择实现局部适应。基于简化基因组测序的分析揭示了南部和北部种群之间轻微的遗传分化信号，尽管种群动态建模支持它们之间持续的历史基因流动。此外，全基因组重测序显示了它们在上一个冰期的独立种群动态历史。因此，这些结果表明，沿盛行洋流的基因流动在一定程度上受到限制，种群并非完全随机交配。此外，基于低覆盖度全基因组测序的选择扫描检测到了与生长相关基因纬度适应的假定基因组特征。因此，我们的综合研究提供了一个在大洋流作用下海洋局部适应的新例子。
