Molecular Ecology and Evolution Lab, Department of Biology, Lund University, Sölvegatan 37, SE-223 62 Lund, SwedenInstitute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland E-mail:
Evolution. 2012 Mar;66(3):720-731. doi: 10.1111/j.1558-5646.2011.01473.x. Epub 2011 Oct 21.
Comparing patterns of diversity and divergence between populations at immune genes and neutral markers can give insights into the nature and geographic scale of parasite-mediated selection. To date, studies investigating such patterns of selection in vertebrates have primarily focused on the acquired branch of the immune system, whereas it remains largely unknown how parasite-mediated selection shapes innate immune genes both within and across vertebrate populations. Here, we present a study on the diversity and population differentiation at the innate immune gene Toll-like receptor 2 (TLR2) across nine populations of yellow-necked mice (Apodemus flavicollis) and bank voles (Myodes glareolus) in southern Sweden. In yellow-necked mice, TLR2 diversity was very low, as was TLR2 population differentiation compared to neutral loci. In contrast, several TLR2 haplotypes co-occurred at intermediate frequencies within and across bank vole populations, and pronounced isolation by distance between populations was observed. The diversity and differentiation at neutral loci was similar in the two species. These results indicate that parasite-mediated selection has been acting in dramatically different ways on a given immune gene in ecologically similar and sympatric species. Furthermore, the finding of TLR2 population differentiation at a small geographical scale in bank voles highlights that vertebrate innate immune defense may be evolutionarily more dynamic than has previously been appreciated.
比较免疫基因和中性标记群体之间的多样性和分化模式，可以深入了解寄生虫介导的选择的性质和地理范围。迄今为止，在脊椎动物中研究这种选择模式的研究主要集中在免疫系统的获得性分支上，而寄生虫介导的选择如何塑造脊椎动物群体内部和群体之间的固有免疫基因在很大程度上仍然未知。在这里，我们研究了在瑞典南部的九个黄颈鼠（Apodemus flavicollis）和林鼠（Myodes glareolus）群体中固有免疫基因 Toll 样受体 2（TLR2）的多样性和种群分化。在黄颈鼠中，TLR2 的多样性非常低，与中性基因座相比，TLR2 的种群分化也很低。相比之下，在林鼠种群内部和种群之间，多个 TLR2 单倍型以中等频率共同出现，并且观察到种群之间明显的距离隔离。两种物种的中性基因座的多样性和分化相似。这些结果表明，寄生虫介导的选择在生态相似和同域的物种中对给定的免疫基因产生了截然不同的影响。此外，在林鼠中发现 TLR2 种群在小地理范围内发生分化，这表明脊椎动物固有免疫防御可能比以前认识到的更具进化动态。
