Data from: Fine-scale spatial covariation between infection prevalence and susceptibility in a natural population

The prevalence of infection varies dramatically on a fine spatial scale. Many evolutionary hypotheses are founded on the assumption that this variation is due to host genetics, such that sites with a high frequency of alleles conferring susceptibility are associated with higher infection prevalence. This assumption is largely untested and may be compromised at finer spatial scales where gene flow between sites is high. We put this assumption to the test in a natural snail-trematode interaction in which host susceptibility is known to have a strong genetic basis. A decade of field sampling revealed substantial spatial variation in infection prevalence between 13 sites around a small lake. Laboratory assays replicated over 3 years demonstrate striking variation in host susceptibility among sites in spite of high levels of gene flow between sites. We find that mean susceptibility can explain more than one-third of the observed variation in mean infection prevalence among sites. We estimate that variation in susceptibility and exposure together can explain the majority of variation in prevalence. Overall, our findings in this natural host-parasite system argue that spatial variation in infection prevalence covaries strongly with variation in the distribution of genetically based susceptibility, even at a fine spatial scale.

感染率在精细空间尺度上存在剧烈波动。诸多进化假说均基于这样一项假设：此类感染率变异源于宿主遗传学差异，即携带高频率易感性等位基因的采样点，其感染率往往更高。这一假设在很大程度上尚未得到验证，且在采样点间基因流较高的更精细空间尺度下，该假设可能不再成立。我们依托一个宿主易感性已被证实具有较强遗传基础的天然蜗牛-吸虫（snail-trematode）互作系统，对该假设开展了检验。十年野外采样结果显示，小型湖泊周边的13个采样点间，感染率存在显著的空间变异。为期三年重复开展的实验室实验测定结果表明，尽管采样点间存在较高水平的基因流，各采样点的宿主易感性仍存在显著变异。我们发现，平均易感性可以解释采样点间平均感染率变异的三分之一以上。经估算，易感性与暴露水平的变异共同作用，可以解释感染率变异的绝大部分。总体而言，我们在该天然宿主-寄生虫系统中获得的研究结果表明，即便在精细空间尺度下，感染率的空间变异与遗传决定的易感性分布变异均存在显著的协同变化关系。