Data from: Mixing of porpoise ecotypes in southwestern UK waters revealed by genetic profiling

Contact zones between ecotypes are windows for understanding how species may react to climate changes. Here, we analysed the fine-scale genetic and morphological variation in harbour porpoises (Phocoena phocoena) around the UK by genotyping 591 stranded animals at nine microsatellite loci. The data were integrated with a prior study to map at high resolution the contact zone between two previously identified ecotypes meeting in the northern Bay of Biscay. Clustering and spatial analyses revealed that UK porpoises are derived from two genetic pools with porpoises from the southwestern UK being genetically differentiated, and having larger body sizes compared to those of other UK areas. Southwestern UK porpoises showed admixed ancestry between southern and northern ecotypes with a contact zone extending from the northern Bay of Biscay to the Celtic Sea and Channel. Around the UK, ancestry blends from one genetic group to the other along a southwest--northeast axis, correlating with body size variation, consistent with previously reported morphological differences between the two ecotypes. We also detected isolation by distance among juveniles but not in adults, suggesting that stranded juveniles display reduced intergenerational dispersal. The fine-scale structure of this admixture zone raises the question of how it will respond to future climate change and provides a reference point for further study.

生态型间的接触带是解析物种响应气候变化机制的关键窗口。本研究针对英国周边海域的港湾鼠海豚（Phocoena phocoena）开展精细尺度的遗传与形态变异分析，通过对591头搁浅个体的9个微卫星位点（microsatellite loci）进行基因分型。本研究整合既往研究数据，以高分辨率绘制了此前在比斯开湾北部交汇的两类生态型间的接触带。聚类与空间分析结果显示，英国周边的港湾鼠海豚源自两个遗传基因库：英国西南部的鼠海豚种群在遗传上存在分化，且体型显著大于英国其他区域的个体。英国西南部的鼠海豚兼具南北两类生态型的混合血统，其接触带从比斯开湾北部延伸至凯尔特海与英吉利海峡。在英国周边海域，遗传血统沿西南-东北轴呈现两类遗传类群的渐渗混合格局，且与体型变异高度相关，这与此前报道的两类生态型间的形态差异完全一致。本研究还在幼体个体中检测到了距离隔离（isolation by distance）效应，但成体种群中未发现该现象，这表明搁浅幼体的跨世代扩散能力有所降低。该混合带的精细尺度结构引发了关于其未来如何响应气候变化的探讨，同时也为后续相关研究提供了重要的基准参照。