Transboundary dispersal: California moray eels exhibit local adaptation in the face of high gene flow. Gymnothorax mordax

We examined population connectivity across nearly the entire adult range of a subtropical Eastern Pacific fish species, the California moray (Gymnothorax mordax). Our objectives were to determine if California morays are genetically homogenous or show distinct genetic structure across different parts of their range, identify signatures of sources/sinks, and examine which environmental or oceanographic processes may contribute to structuring populations. We used restriction site-associated sequencing (RADseq) to examine genetic diversity across 252 individuals from 11 locations. We used satellite data to examine whether environmental characteristics at the time of settlement were correlated with patterns of local adaptation. We found high gene flow across all locations, though a small subset of loci showed strong signs of local adaptation. Patterns of local adaptation were correlated with sea surface temperature, sea surface temperature anomaly, and sea surface height at the time of settlement, but not with geographic distance. Genes under selection have been implicated in teleost eye development, reproduction, and stress. Despite high gene flow, California morays exhibit local adaptation with phenotype-environment mismatches during the late larval/early juvenile stages ultimately constraining the species range. Our study supports a long-standing hypothesis that morays in southern California have limited local reproduction.

本研究针对亚热带东太平洋鱼类物种加州裸胸鳝（Gymnothorax mordax）的几乎整个成体分布范围开展种群连通性分析。本研究旨在明确加州裸胸鳝种群在其分布区内是否呈现遗传均一性，抑或在不同区域存在显著遗传结构分化；识别源/汇种群特征，并解析驱动种群结构形成的环境或海洋学过程。本研究采用限制性位点关联测序（restriction site-associated sequencing, RADseq）技术，对来自11个采样点的252尾个体开展遗传多样性分析；同时借助卫星遥感数据，探究幼体定居时期的环境特征与本地适应模式的相关性。研究结果显示，所有采样点间均存在较高的基因流，但少数基因座呈现出显著的本地适应特征。本地适应模式与幼体定居时期的海表温度、海表温度距平及海表高度显著相关，但与地理距离无关联。受选择作用的基因涉及硬骨鱼的眼睛发育、繁殖及应激响应过程。尽管存在较高的基因流，加州裸胸鳝仍表现出本地适应特征；幼体晚期至幼体早期阶段出现的表型-环境错配现象，最终限制了该物种的分布范围。本研究验证了一项长期存在的学术假说：南加州海域的裸胸鳝种群本地繁殖能力有限。