If parasites transmit more readily between closely related hosts, then parasite burdens should decrease with increased genetic diversity of host populations. This important hypothesis is often accepted at face value—notorious epidemics of crop monocultures testify to the vulnerability of host populations that have been purged of diversity. Yet the relationship between genetic diversity and parasitism likely varies across contexts, differing between crop and noncrop hosts and between experimental and natural host populations. Here, we used a meta‐analytic approach to ask if host diversity confers protection against parasites over the range of contexts in which it has been tested. We synthesized the results of 102 studies, comprising 2004 effect sizes representing a diversity of approaches and host‐parasite systems. Our results validate a protective effect of genetic diversity, while revealing significant variation in its strength across biological and empirical contexts. In experimental host populations, genetic diversity reduces parasitism by ∼20% for noncrop hosts and by ∼50% for crop hosts. In contrast, observational studies of natural host populations show no consistent relationship between genetic diversity and parasitism, with both strong negative and positive correlations reported. This result supports the idea that, if parasites preferentially attack close relatives, the correlation of genetic diversity with parasitism could be positive or negative depending upon the potential for host populations to evolve in response to parasite selection. Taken together, these results reinforce genetic diversity as a priority for both conservation and agriculture and emphasize the challenges inherent to drawing comparisons between controlled experimental populations and dynamic natural populations.

中文翻译：

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遗传多样性是否能保护寄主种群免受寄生虫侵害？跨自然和农业系统的荟萃分析

如果寄生虫在密切相关的宿主之间更容易传播，那么寄生虫的负担应随着宿主种群遗传多样性的增加而减少。这个重要的假设通常从表面上被接受-农作物单一文化的臭名昭著的流行证明了被清除多样性的寄主种群的脆弱性。然而，遗传多样性与寄生虫之间的关系可能会因环境而异，农作物和非农作物寄主之间以及实验和自然寄主种群之间都存在差异。在这里，我们使用了荟萃分析的方法来询问宿主多样性是否在经过测试的环境范围内赋予了针对寄生虫的保护。我们综合了102项研究的结果，其中包括2004年影响的大小，代表了不同方法和宿主-寄生虫系统的影响。我们的结果验证了遗传多样性的保护作用，同时揭示了其在生物学和经验背景下强度的显着变化。在实验寄主种群中，遗传多样性使非农作物寄主的寄生虫减少约20％，而对农作物寄主的寄生虫减少约50％。相反，对自然寄主种群的观察研究表明，遗传多样性与寄生性之间没有一致的关系，据报道两者具有强的负相关和正相关。这个结果支持这样一个观点，即如果寄生虫优先攻击近亲，则遗传多样性与寄生虫的相关性可能是正的或负的，这取决于寄主种群响应于寄生虫选择而进化的潜力。在一起