Data from: Genetic drift during the spread phase of a biological invasion

Recent theoretical and experimental models have evidenced the role played
by evolution during species spread, and particularly question the
influence of genetic drift at range edges. By investigating the spread of
an aquatic invader in patchy habitats, we quantified genetic drift and
explored its consequences on genetic diversity and fitness. We examined
the interplay of gene flow and genetic drift in 36 populations of the red
swamp crayfish, Procambarus clarkii, in a relatively recently invaded
wetland area (30 years, Brière, northwestern France). Despite the small
spatial scale of our study (15 km²), populations were highly structured
according to the strong barrier of land surfaces and revealed a clear
pattern of colonisation through watercourses. Isolated populations
exhibited small effective sizes and low dispersal rates that depended on
water connectivity, suggesting that genetic drift dominated in the
evolution of allele frequencies in these populations. We also observed a
significant decrease in the genetic diversity of isolated populations over
only a two-year period, but failed to demonstrate an associated fitness
cost using fluctuating asymmetry. This study documents the possible strong
influence of genetic drift during the spread of a species, and such
findings provide critical insights in the current context of profound
rearrangements in species distributions due to global change.

近年来的理论与实验模型均证实了演化在物种扩散进程中的核心作用，并针对性地质疑了物种分布边界处遗传漂变（genetic drift）的影响。本研究以栖息于斑块生境中的水生入侵物种为研究对象，通过追踪其扩散过程量化了遗传漂变，并探讨了其对遗传多样性与适合度的影响。我们以法国西北部布里耶尔（Brière）一处入侵时长约30年的湿地中的36个克氏原螯虾（Procambarus clarkii，红沼泽小龙虾）种群为研究样本，分析了基因流（gene flow）与遗传漂变之间的相互作用。尽管本研究的空间尺度仅为15平方千米，但陆地构成了较强的扩散屏障，种群间呈现出显著的遗传结构，并展现出通过水系完成定殖的清晰模式。孤立种群的有效种群大小（effective population size）规模较小，且扩散速率依赖于水系连通性且处于较低水平，这表明遗传漂变主导了这些种群的等位基因频率演化。我们还观察到，仅在两年的时间跨度内，孤立种群的遗传多样性便出现了显著下降，但通过波动不对称性（fluctuating asymmetry）分析未能证实这一现象伴随适合度成本。本研究证实了遗传漂变在物种扩散过程中可能发挥的强烈作用，在当前全球变化导致物种分布发生剧烈重塑的背景下，该研究结果为相关领域提供了至关重要的理论参考。