Data from: Contracting patterns of diversity and population differentiation at the innate immunity gene Toll-like receptor 2 (TLR2) in two sympatric rodent species

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 defence may be evolutionarily more dynamic than has previously been appreciated.

比较免疫基因与中性标记（neutral markers）在不同种群间的多样性与分化模式，可阐明寄生虫介导选择的本质特征与地理作用范围。迄今为止，针对脊椎动物此类选择模式的研究主要聚焦于免疫系统的获得性分支，而寄生虫介导选择如何塑造脊椎动物种群内部及跨种群的先天免疫基因，目前仍知之甚少。本研究针对瑞典南部9个种群的黄颈姬鼠（Apodemus flavicollis）与普通田鼠（Myodes glareolus）的先天免疫基因Toll样受体2（Toll-like receptor 2, TLR2）的多样性及种群分化展开分析。在黄颈姬鼠中，TLR2的多样性及其种群分化程度均远低于中性基因座。与之相反，普通田鼠的种群内部及跨种群中均存在多种TLR2单倍型以中等频率共存，且种群间呈现显著的距离隔离效应。两种中性基因座的多样性与分化程度在两个物种中表现相似。上述结果表明，对于生态位相似且同域分布的物种而言，寄生虫介导选择对同一免疫基因的作用模式存在显著差异。此外，普通田鼠TLR2种群分化在较小地理尺度下即可被检测到这一发现，提示脊椎动物的先天免疫防御在演化层面可能比此前认知的更为动态可变。