Species distributions have been profoundly affected by past climate change, and are expected to change considerably in response to future environmental change. To better apprehend how future climate change is likely to affect genetic diversity in marine populations, it is essential to first evaluate the processes that have shaped the current distribution of genetic diversity in the sea. The honeycomb worm is a reef-building polychaete that hosts high biodiversity. Here we show that the genetic diversity in populations of S. alveolata is highest towards the edges of the current species range and lowest at its center. Pleistocene glacial cycles likely led to extirpations of S. alveolata from central populations in the Bay of Biscay, with coalescent-based estimates of post-glacial colonization dating to the beginning of the Holocene interglacial, from 10,000 to 14,000 years ago. Meanwhile, populations in the Irish Sea and English Channel likely persisted in glacial refugia since the Eemian interglacial, 120,000 years ago. Northern populations host at least two sets of divergent haplotypes, indicating that two refugia possibly existed in the north, with Ireland being a likely second refugium. Within biogeographic regions, populations were overall well-connected, but strong genetic differentiation suggests that little exchange occurs between regions. These two unexpected reservoirs of genetic diversity at the range edges deserve greater attention as warming temperatures threaten trailing edge populations, while greater climatic variability threatens leading edge populations.

过去的气候变化对物种的分布产生了深远的影响，并有望随着未来的环境变化而发生很大的变化。为了更好地理解未来的气候变化可能如何影响海洋种群的遗传多样性，必须首先评估影响海洋遗传多样性当前分布的过程。蜂窝蠕虫是一种拥有高生物多样性的造礁珊瑚。在这里，我们表明，S。alveolata种群的遗传多样性在当前物种范围的边缘最高，而在其中心最低。更新世的冰川周期可能导致S. alveolata的灭绝来自比斯开湾的中心人口，基于聚结的冰期后殖民时期的估算可追溯到10,000至14,000年前全新世间冰期开始。同时，自12万年前的Eemian跨冰期以来，爱尔兰海和英吉利海峡的人口很可能仍在进行冰期避难。北部人口至少拥有两组不同的单倍型，这表明北部可能存在两种避难所，爱尔兰可能是第二避难所。在生物地理区域内，种群总体上联系良好，但是强大的遗传分化表明区域之间几乎没有交换。由于气温升高威胁到后缘种群，这两个在范围边缘的未曾预料到的遗传多样性储藏库值得进一步关注。