Marine Genomics Laboratory, Department of Life Sciences, Texas A&M University-Corpus Christi, Corpus Christi, Texas, USA.
Department of Biology, Saint Anselm College, Manchester, New Hampshire, USA.
Mol Ecol. 2023 Sep;32(18):4953-4970. doi: 10.1111/mec.17096. Epub 2023 Aug 11.
Understanding how interactions among microevolutionary forces generate genetic population structure of exploited species is vital to the implementation of management policies that facilitate persistence. Philopatry displayed by many coastal shark species can impact gene flow and facilitate selection, and has direct implications for the spatial scales of management. Here, genetic structure of the blacktip shark (Carcharhinus limbatus) was examined using a mixed-marker approach employing mitochondrial control region sequences and 4339 SNP-containing loci generated using ddRAD-Seq. Genetic variation was assessed among young-of-the-year sampled in 11 sites in waters of the United States in the western North Atlantic Ocean, including the Gulf of Mexico. Spatial and environmental analyses detected 68 nuclear loci putatively under selection, enabling separate assessments of neutral and adaptive genetic structure. Both mitochondrial and neutral SNP data indicated three genetically distinct units-the Atlantic, eastern Gulf, and western Gulf-that align with regional stocks and suggest regional philopatry by males and females. Heterogeneity at loci putatively under selection, associated with temperature and salinity, was observed among sites within Gulf units, suggesting local adaptation. Furthermore, five pairs of siblings were identified in the same site across timescales corresponding with female reproductive cycles. This indicates that females re-used a site for parturition, which has the potential to facilitate the sorting of adaptive variation among neighbouring sites. The results demonstrate differential impacts of microevolutionary forces at varying spatial scales and highlight the importance of conserving essential habitats to maintain sources of adaptive variation that may buffer species against environmental change.
了解微观进化力量如何相互作用，从而产生受捕捞物种的遗传种群结构，对于实施有助于物种持续生存的管理政策至关重要。许多沿海鲨鱼物种的亲代护幼行为会影响基因流动并促进选择，这对管理的空间尺度有直接影响。本研究采用混合标记方法，利用线粒体控制区序列和 ddRAD-Seq 生成的 4339 个含有 SNP 的位点，研究了黑鳍鲨（Carcharhinus limbatus）的遗传结构。评估了在北大西洋西墨西哥湾的 11 个地点采集的幼鱼的遗传变异，包括墨西哥湾。空间和环境分析检测到 68 个核基因座可能受到选择，这使中性和适应性遗传结构的单独评估成为可能。线粒体和中性 SNP 数据都表明存在三个遗传上不同的单元——大西洋、东墨西哥湾和西墨西哥湾——与区域种群一致，并表明雌雄个体的区域亲代护幼行为。在海湾单元内的各地点观察到与温度和盐度相关的假定选择位点的异质性，表明存在局部适应。此外，在同一地点的不同时间尺度上发现了五对兄弟姐妹，这与雌性生殖周期相对应。这表明雌性会重新使用一个产仔地点，这有可能促进相邻地点适应性变异的分类。研究结果表明，微观进化力量在不同空间尺度上的影响不同，并强调了保护重要栖息地以维持适应性变异来源的重要性，这可能缓冲物种对环境变化的影响。
