Data from: Mixing of porpoise ecotypes in south western 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 9 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 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 SW-NE 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探究物种如何响应气候变化的重要研究窗口。本研究针对英国周边海域的港湾鼠海豚（Phocoena phocoena）展开分析：通过对9个微卫星位点（microsatellite loci）进行基因分型，共检测了591头搁浅个体的精细尺度遗传与形态变异。本研究将本次数据与既往研究整合，以高分辨率绘制了此前在比斯开湾北部发现的两种生态型之间的接触带。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，其中英国西南部的鼠海豚遗传分化显著，且体型较英国其他海域的个体更大。英国西南部的鼠海豚呈现出南北两种生态型的祖源混合特征，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，祖源沿西南-东北轴从一个遗传类群逐渐过渡至另一个，该梯度与体型变异高度相关，与此前报道的两种生态型间的形态差异相符。本研究还发现幼体存在距离隔离效应，而成体则无此现象，这表明搁浅幼体的跨代扩散能力有所降低。该混合带的精细尺度结构引发了其将如何响应未来气候变化的疑问，同时也为后续研究提供了参考基准。