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态势，需先明确其媒介物种的分布扩张机制。本研究针对魁北克南部的13个莱姆病（Lyme disease）传播媒介黑腿蜱（black-legged tick）种群，开展了遗传结构的时空变异特征分析——该区域目前正处于黑腿蜱的扩张阶段，莱姆病亦呈新发态势。本研究的核心目标是基于观测到的遗传结构时空模式，明确黑腿蜱迁入加拿大的主要传播路径。本研究对613份黑腿蜱样本的10个微卫星位点（microsatellite loci）进行基因分型后，检测到多次长距离扩散事件的多重遗传信号，这一结果支持"候鸟是黑腿蜱迁入魁北克南部的主要携带媒介"这一假说。通过对比2011至2014年间不同年份、8个采样点的黑腿蜱个体间两两差异分析结果，我们发现：相较于采样地点，采样年份能更好地解释黑腿蜱个体间的遗传变异。这表明：尽管黑腿蜱种群可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，研究区域内黑腿蜱种群的遗传变异水平与其定殖程度相关：定殖种群的时间尺度遗传变异水平显著低于偶殖种群。鉴于某一区域的莱姆病感染风险可受定殖种群与/或偶殖种群的相对占比影响，本研究结果有助于同时解析莱姆病的季节动态与空间变异特征。