Department of Animal Ecology, Lund University, Lund, Sweden.
J Evol Biol. 2011 Jan;24(1):159-67. doi: 10.1111/j.1420-9101.2010.02148.x. Epub 2010 Oct 21.
The genetic structure of a pathogen is an important determinant of its potential rate of adaptation and can thereby influence the dynamics of host-parasite interactions. We investigated how the genetic structure of Borrelia afzelii varies with geographic and ecological sampling scale. Genetic structure was measured as the degree of linkage disequilibrium (LD) across three loci. To test for the effects of geographic and ecological scale, we calculated LD across or within populations 4-82 km apart and across or within different mammal host species. There was highly significant LD across populations and host species. However, there was also evidence for genome-wide recombination, and the LD largely resulted from epidemic spread of certain haplotypes, rather than lack of recombination. Interestingly, the degree of LD was higher in each population than in the sample as a whole, i.e. LD increased with decreasing geographic scale. In contrast, there was no effect of ecological sampling scale on LD. Strong LD may impede the rate of adaptive evolution. Our results suggest this effect might be particularly strong at a small geographic scale.
病原体的遗传结构是其潜在适应速度的重要决定因素，从而影响宿主-寄生虫相互作用的动态。我们研究了伯氏疏螺旋体的遗传结构如何随地理和生态采样规模而变化。遗传结构通过三个基因座的连锁不平衡（LD）程度来衡量。为了检验地理和生态尺度的影响，我们计算了相距 4-82 公里的种群之间或种群内部以及不同哺乳动物宿主物种之间的 LD。种群之间和宿主物种之间存在高度显著的 LD。然而，也有证据表明全基因组重组，LD 主要是由于某些单倍型的流行传播，而不是缺乏重组。有趣的是，每个种群的 LD 程度都高于整个样本，即 LD 随着地理尺度的减小而增加。相比之下，生态采样尺度对 LD 没有影响。强 LD 可能会阻碍适应性进化的速度。我们的研究结果表明，这种影响在小地理尺度上可能特别强烈。
