Data from: Local and regional founder effects in lake zooplankton persist after thousands of years despite high dispersal potential

We reconstructed the genetic structure of a planktonic crustacean Daphnia longispina living in high mountain lakes and ponds in the Pyrenees to investigate whether it was shaped by persistent founder effects originating shortly after the last glacial maximum or by ongoing dispersal and effective migration (gene flow). We found that the genetic structure can largely be explained by a single colonization event following gradual deglaciation of the Pyrenees c. 10-15 000 years ago. Nuclear genetic diversity declined steeply from southeast to northwest, suggestive of serial colonization of available habitats with advancing deglaciation. The spatial genetic structure suggests that founder effects were major determinants of the present-day diversity, both at the catchment level and at the level of individual water bodies, further supporting extremely low effective migration rates. This study reveals a prime example of a founder effect that is both long-lasting and maintained at small spatial scales. Our data suggest a process of isolation by colonisation as a result of strong priority effects and monopolisation. We found evidence for the spread of haplotypes with Pyrenean ancestry across the Palearctic over distances up to 5500 km, although the local genetic structure after colonization was hardly influenced by contemporary dispersal. Finally, our data also suggest that mitochondrial mutation rates in the studied populations were seven times higher than typically assumed. Overall, we show that founder effects can persist for centuries even at small spatial scales at which the potential for dispersal is high.

我们对栖息于比利牛斯山脉高山湖泊与池塘中的浮游甲壳类长肢溞（Daphnia longispina）的遗传结构进行了重构，旨在探究其遗传结构是由末次冰盛期后不久产生的持续性奠基者效应（founder effect）塑造，还是由持续的扩散与有效迁移（基因流，gene flow）所决定。研究结果显示，该物种的遗传结构在很大程度上可由约1万至1.5万年前比利牛斯山脉逐步冰川消融后的单次定殖事件解释。核遗传多样性从东南向西北急剧下降，这表明随着冰川消融推进，该物种通过一系列连续定殖过程占据了可利用的生境。空间遗传结构表明，无论是在流域尺度还是单个水体尺度，奠基者效应均为现今遗传多样性的主要决定因素，这进一步佐证了极低的有效迁移率。本研究揭示了一个兼具持久性且在小空间尺度上得以维持的奠基者效应的典型案例。我们的数据表明，由于强烈的优先效应与生境垄断，定殖过程引发了隔离效应。我们发现携带比利牛斯山脉起源的单倍型（haplotype）在古北界（Palearctic）范围内扩散的证据，扩散距离可达5500公里，尽管定殖后的局部遗传结构几乎不受当代扩散的影响。最后，我们的数据还显示，所研究种群的线粒体突变率比通常假设的高出7倍。总而言之，本研究证实，即便在扩散潜力较高的小空间尺度上，奠基者效应仍可存续数百年。