Aedes aegypti in North America (Microsatellite and SNP array)

The Aedes aegypti mosquito first invaded the Americas about 500 years ago and today is a widely distributed invasive species and the primary vector for viruses causing dengue, chikungunya, Zika, and yellow fever. Here we test the hypothesis that the North American colonization by Ae. aegypti occurred via a series of founder events. We present findings on genetic diversity, structure, and demographic history using data from 70 Ae. aegypti populations in North America genotyped at 12 microsatellite loci and/or ~20,000 single nucleotide polymorphisms (SNPs), the largest genetic study of the region to date. We find evidence consistent with a colonization driven by serial founder effect (SFE), with Florida as the putative source for a series of westward invasions. This scenario was supported by 1) a decrease in the genetic diversity of Ae. aegypti populations moving west, 2) a correlation between pairwise genetic and geographic distances, and 3) demographic analysis based on allele frequencies. A few Ae. aegypti populations on the west coast do not follow the general trend, likely due to a recent and distinct invasion history. We argue that SFE provides a helpful albeit simplified model for the movement of Ae. aegypti across North America, with outlier populations warranting further investigation.

埃及伊蚊（Aedes aegypti）约于500年前首次入侵美洲，如今已是广泛分布的入侵物种，同时作为登革热、基孔肯雅热、寨卡病毒病及黄热病相关病毒的主要传播媒介。本研究验证了"埃及伊蚊经一系列奠基者事件（founder events）定殖北美"这一假说，利用北美70个埃及伊蚊种群的基因分型数据——这些种群在12个微卫星位点（microsatellite loci）及/或约20000个单核苷酸多态性（SNPs）位点完成基因分型——分析了其遗传多样性、种群结构及种群历史动态，是目前该区域规模最大的相关遗传学研究。我们发现的证据支持：北美埃及伊蚊的定殖过程由连续奠基者效应（SFE）驱动，且佛罗里达或为一系列西向入侵的源头种群。该推论得到以下三方面证据的支撑：其一，西向扩散的埃及伊蚊种群遗传多样性逐步降低；其二，种群间的遗传距离与地理距离呈显著相关；其三，基于等位基因频率的种群历史动态分析结果亦支持该模型。西海岸的少数埃及伊蚊种群未遵循这一总体趋势，这大概率与其近期独特的入侵历史有关。我们认为，尽管连续奠基者效应模型较为简化，但仍可为埃及伊蚊在北美的扩散模式提供合理的解释框架；而那些偏离总体趋势的种群则有待进一步深入研究。