Data from: Genetic signature of range expansion of a disease vector - the black-legged tick

Monitoring and predicting the spread of emerging infectious diseases requires that we understand the mechanisms of range expansion by its vectors. Here, we examined spatial and temporal variation of genetic structure among 13 populations of the Lyme disease vector, the black-legged tick, in southern Quebec, where this tick species is currently expanding and Lyme disease is emerging. Our objective was to identify the primary mode of tick movement into Canada based on observed spatial and temporal genetic patterns. Upon genotyping ten microsatellite loci from 613 tick specimens, Wwe found multiple genetic signatures of frequent long-distance dispersal events, supporting the hypothesis that migratory birds are the primary carriers of black-legged ticks into southern Quebec. When we compared results from analyses of pairwise differences among ticks collected from eight different sites at different years between 2011 and 2014, we found that genetic variation observed among tick individuals appeared to be better explained by collection year than sampling locality. This suggests that while cohorts of black-legged ticks can rapidly invade large areas across southern Quebec, they also appear to be undergoing frequent turnover. Finally, the amount of genetic variation in tick populations across our study area appeared to be related to their degree of establishment, with established populations displaying a lower amount of temporal genetic variation than adventitious ones. Given that Lyme disease infection risk in a region can be influenced by the relative presence of established and/or adventitious tick populations, our results are useful for understanding both the seasonality and spatial variation of Lyme disease.监测与预测新发传染病的传播，需要我们明晰其媒介物种的分布扩张机制。本研究针对魁北克南部13个莱姆病（Lyme disease）媒介——黑脚硬蜱（black-legged tick）种群的遗传结构时空变异展开分析——该区域目前正处于该蜱种的分布扩张阶段，莱姆病也呈新发态势。本研究的目标是基于观测到的遗传结构时空模式，明确该蜱类迁入加拿大的主要传播途径。研究团队对613份蜱类标本的10个微卫星位点（microsatellite loci）进行基因分型后，检测到频繁发生长距离扩散事件的多重遗传信号，支持了“候鸟是黑脚硬蜱迁入魁北克南部的主要携带者”这一假说。通过对比2011至2014年间不同年份、8个采样点的蜱类个体间成对差异分析结果，研究团队发现，蜱类个体的遗传变异更易由采样年份而非采样地点来解释。这表明，尽管黑脚硬蜱种群能够快速扩散至魁北克南部的大片区域，但其种群也正经历频繁的更替过程。最后，研究区域内蜱类种群的遗传变异总量与其定殖程度呈相关关系：已成功定殖的种群，其时间尺度上的遗传变异水平显著低于偶发性迁入种群。鉴于某一区域的莱姆病感染风险会受到该区域内定殖与/或偶迁入蜱类种群相对占比的影响，本研究结果有助于解析莱姆病传播的季节动态与空间变异特征。