Environmental conditions were particularly severe during the Last Glacial Maximum, altering the distribution of the Southern Hemisphere biota, particularly at higher latitudes. The copepod Boeckella poppei is the only macroscopic continental invertebrate species known to be distributed today across the three main biogeographic regions in Antarctica as well as in southern South America. Signy Island (South Orkney Islands) is a unique location for the study of Antarctic freshwater ecosystems due to its location and geographic isolation; it contains 17 lakes in several low altitude catchments. We conducted phylogeographic and demographic analyses using the cox1 gene on 84 individuals of B. poppei from seven lakes across Signy Island. We recorded low levels of genetic diversity and a strong genetic differentiation signal between the eastern and western valleys within the island. Phylogeographic structure and demographic inference analyses suggested at least one asymmetrical dispersal event from west to east. Demographic inference detected a strong signal of population growth during the deglaciation process, which may have followed either (1) a strong genetic bottleneck due to a reduction in population size during the last glacial period, or (2) a founder effect associated with postglacial recolonization of Signy Island from elsewhere. The genetic architecture of this island's populations of B. poppei shows that historical events, rather than continuous dispersal events, likely played a major role in the species' current distribution. Finally, our study considers possible mechanisms for dispersal and colonization success of the most dominant species in the Antarctic freshwater community.

中文翻译：

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南奥克尼群岛西尼岛上湖中南极淡水co足类波克氏菌的强烈小规模种群结构的证据

在最后一次冰川最大时期，环境条件特别严峻，这改变了南半球生物群的分布，特别是在高纬度地区。pe足类波克氏菌是当今已知的唯一在南极洲和南美南部三个主要生物地理区域中分布的宏观大陆无脊椎动物。西尼岛（南奥克尼群岛）因其地理位置和地理隔离而成为研究南极淡水生态系统的独特地点；它包含几个低海拔流域的17个湖泊。我们使用cox 1基因对84株罂粟双歧杆菌进行了系统地理学和人口统计学分析来自Signy Island的七个湖泊。我们记录到该岛东部和西部山谷之间的遗传多样性水平很低，而遗传信号却很强。系谱结构和人口统计学分析表明，至少发生了一次从西到东的不对称扩散事件。人口统计学推断在冰消冰过程中出现了人口增长的强烈信号，这可能是由于（1）由于上一个冰川期人口规模减少而造成的强大的基因瓶颈，或者（2）与冰川后再殖民化有关的奠基者效应来自其他地方的Signy Island。该岛上流行双歧杆菌种群的遗传结构表明历史事件而不是连续的传播事件可能在该物种的当前分布中发挥了重要作用。最后，我们的研究考虑了南极淡水群落中最主要物种的扩散和定殖成功的可能机制。