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（ecotype）间的接触带是探究物种响应气候变化机制的重要窗口。本研究通过对英国周边海域591头搁浅的港湾鼠海豚（Phocoena phocoena）的9个微卫星位点（microsatellite loci）进行基因分型，分析了其精细尺度下的遗传与形态变异。本研究将此次数据与既往研究相结合，对此前在比斯开湾北部交汇的两种生态型间的接触带开展了高分辨率制图。聚类分析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；其中英国西南部的种群不仅在遗传上存在分化，其体型也较英国其他区域的个体更大。英国西南部的港湾鼠海豚呈现出南方与北方生态型的混合血统，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，种群血统沿西南-东北轴从一个遗传类群渐变为另一个，该梯度与体型变异呈显著相关，与此前报道的两种生态型间的形态差异一致。本研究还在幼体群体中检测到了距离隔离（isolation-by-distance）效应，但成体群体中并未发现该现象，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关于其未来如何响应气候变化的科学疑问，同时也为后续相关研究提供了重要参考基准。