Data from: Genetic structure, admixture, and invasion success in a Holarctic defoliator, the gypsy moth (Lymantria dispar, Lepidoptera: Erebidae)

Characterizing the current population structure of potentially invasive species provides a critical context for identifying source populations and for understanding why invasions are successful. Non-native populations inevitably lose genetic diversity during initial colonization events, but subsequent admixture among independently introduced lineages may increase both genetic variation and adaptive potential. Here we characterize the population structure of the gypsy moth (Lymantria dispar Linnaeus), one of the world's most destructive forest pests. Native to Eurasia and recently introduced to North America, the current distribution of gypsy moth includes forests throughout the temperate region of the northern hemisphere. Analyses of microsatellite loci and mitochondrial DNA sequences for 1738 individuals identified four genetic clusters within L. dispar. Three of these clusters correspond to the three named subspecies; North American populations represent a distinct fourth cluster, presumably a consequence of the population bottleneck and allele frequency change that accompanied introduction. We find no evidence that admixture has been an important catalyst of the successful invasion and range expansion in North America. However, we do find evidence of ongoing hybridization between subspecies and increased genetic variation in gypsy moth populations from Eastern Asia, populations that now pose a threat of further human-mediated introductions. Finally, we show that current patterns of variation can be explained in terms of climate and habitat changes during the Pleistocene, a time when temperate forests expanded and contracted. Deeply diverged matrilines in Europe imply that gypsy moths have been there for a long time and are not recent arrivals from Asia.解析潜在入侵物种当前的种群结构，可为确定其入侵源种群、阐释入侵成功的内在机制提供关键依据。外来种群在初始定殖过程中不可避免会丢失遗传多样性，但后续独立引入的谱系间的遗传混合，或可提升其遗传变异水平与适应潜能。本研究针对全球极具破坏性的森林害虫之一——舞毒蛾（Lymantria dispar Linnaeus），解析其种群结构。该虫原生分布于欧亚大陆，近年传入北美，当前其分布覆盖北半球温带区域的各类森林生态系统。研究团队通过对1738个个体的微卫星位点（microsatellite loci）与线粒体DNA（mitochondrial DNA）序列开展分析，在舞毒蛾中鉴定出4个遗传聚类群。其中3个聚类群对应已定名的3个亚种；北美种群则构成独立的第4个聚类群，推测这是传入过程中遭遇种群瓶颈、等位基因频率改变所导致的结果。本研究未发现遗传混合是北美舞毒蛾成功入侵与分布范围扩张的关键诱因的相关证据。但本研究发现，亚种间存在持续的杂交现象，且东亚地区的舞毒蛾种群遗传变异水平有所提升——这类种群当前存在进一步通过人类活动介导传入其他区域的风险。最后，本研究证实，当前的遗传变异模式可通过更新世（Pleistocene）时期的气候与栖息地变化得到阐释——该时期温带森林经历了扩张与收缩的循环。欧洲地区存在分化程度极高的母系谱系，表明舞毒蛾在当地已存续许久，并非近年从亚洲传入的类群。