Génétique et Evolution des Maladies Infectieuses, UMR CNRS-IRD 2724, IRD, 911 avenue Agropolis, BP 64501, 34394 Montpellier Cedex 5, France.
Infect Genet Evol. 2010 Oct;10(7):989-97. doi: 10.1016/j.meegid.2010.06.003. Epub 2010 Jun 19.
Population genetics can help us better understand species microevolution and population biology, but inferences made from the genetic polymorphisms of field-collected organisms critically rely on sampling design. The population structure of the tick Ixodes ricinus L. (Acari, Ixodidae), a commonly encountered ectoparasite and the principal vector of human Lyme disease in Europe, has been the focus of some study, but many ecological aspects of this species remain poorly understood. Here, we apply a Bayesian clustering approach to observed and simulated data to examine within-population structure in I. ricinus, and to re-analyse patterns of sex-biased dispersal based on this substructure. We found between 18 and 27 distinct clusters within each of the 12 subsamples examined with a significant drop of heterozygote deficits. Parallel analyses on a comparable species, the seabird tick Ixodes uriae, indicated that these clusters can reflect important ecological features of the species (i.e., local host-associations). Analyses that considered the within-population clustering pattern of I. ricinus showed reversed patterns of sex-biased dispersal as compared to raw data (i.e., female-biased instead of male-biased dispersal). Simulated data supported the hypothesis that these scale-dependant patterns could be due to a combination of sex-specific dispersal and mortality. These different results raise new questions on the dispersal and host use strategies of I. ricinus and the potential importance of these ecological features for disease transmission. Furthermore, this work underlines the importance of taking into account patterns of genetic substructure when investigating sex-biased dispersal in natural populations.
群体遗传学可以帮助我们更好地理解物种的微观进化和种群生物学，但从野外采集的生物体的遗传多态性中得出的推论，关键依赖于采样设计。硬蜱（蜱螨目，硬蜱科）是一种常见的外寄生虫，也是欧洲人类莱姆病的主要传播媒介，其种群结构一直是一些研究的重点，但该物种的许多生态方面仍了解甚少。在这里，我们应用观察和模拟数据的贝叶斯聚类方法来研究硬蜱的种群内结构，并根据这种亚结构重新分析性别偏向扩散的模式。我们在 12 个样本中的每一个样本中都发现了 18 到 27 个不同的聚类，杂合子缺失显著减少。对相似物种——海鸟蜱——的平行分析表明，这些聚类可以反映该物种的重要生态特征（即，局部宿主关联）。考虑到硬蜱的种群内聚类模式的分析显示，与原始数据相比，性别偏向扩散的模式发生了反转（即雌性偏向而不是雄性偏向的扩散）。模拟数据支持了这样一种假设，即这些依赖于尺度的模式可能是由于性别特异性扩散和死亡率的组合所致。这些不同的结果对硬蜱的扩散和宿主利用策略提出了新的问题，以及这些生态特征对疾病传播的潜在重要性。此外，这项工作强调了在调查自然种群中性别偏向扩散时，考虑遗传亚结构模式的重要性。
