Data from: Phenotypic and genetic divergence among harbour porpoise populations associated with habitat regions in the North Sea and adjacent seas.

Determining the mechanisms that generate population structure is essential to the understanding of speciation and the evolution of biodiversity. Here, we investigate a geographic range that transects two habitat gradients, the North Sea to North Atlantic transition, and the temperate to sub-polar regions. We studied the harbour porpoise (Phocoena phocoena), a small odontocete inhabiting both sub-polar and temperate waters. To assess differentiation among putative populations we measured morphological variation at cranial traits (N=462 individuals) and variation at eight microsatellite loci for 338 of the same individuals from Norwegian, British and Danish waters. Significant morphological differentiation reflected the size of the buccal cavity. Porpoises forage in relatively shallow waters preying mainly on benthic species in British and Danish waters, and on mesopelagic and pelagic fish off the coast of Norway. We suggest that the observed differentiation may be explained by resource specialization and either adaptation or developmental responses to different local habitats.

阐明驱动种群结构（population structure）形成的机制，对于理解物种形成与生物多样性演化至关重要。本研究聚焦横穿两类生境梯度的地理分布区：即北海至北大西洋的过渡带，以及温带至亚极地的过渡区域。我们以港湾鼠海豚（*Phocoena phocoena*）为研究对象，这是一类栖息于亚极地与温带水域的小型齿鲸类（odontocete）。为评估推测种群间的分化程度，我们对462个个体的颅骨性状（cranial traits）形态变异，以及来自挪威、英国与丹麦海域的338份同批次个体的8个微卫星位点（microsatellite loci）的遗传变异进行了检测。观测到的显著形态分化与颊腔（buccal cavity）大小密切相关：在英国与丹麦海域，鼠海豚多在相对浅水区觅食，主要捕食底栖物种（benthic species）；而挪威近海的鼠海豚则以中层与远洋鱼类（mesopelagic and pelagic fish）为食。我们认为，本次观测到的种群分化可通过资源特化，以及对不同本地生境的适应或发育响应得到合理解释。