Antagonistic coevolution with parasites maintains host genetic diversity: an experimental test
Antagonistic coevolution with parasites maintains host genetic diversity: an experimental test
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DOI：
10.1098/rspb.2010.1211
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发表时间：
2011-01-22
影响因子：
4.7
通讯作者：
Schmid-Hempel, Paul
中科院分区：
文献类型：
--
作者：
Berenos, Camillo;Wegner, K. Mathias;Schmid-Hempel, Paul
自然种群的遗传变异是种群对自然选择做出反应的首要先决条件，但也经常受到一些因素的威胁，比如遗传漂变和多种自然选择。霍尔丹强调了寄生虫作为遗传多样性驱动力的潜在重要性。从那以后，他的理论就被认为是理所当然的，但是尽管有大量的研究表明遗传多样性和寄生之间存在相关性，霍尔丹的假设很少得到实验的明确支持。为了验证两种独立的进化力量（漂变和寄生虫诱导选择）对遗传变异维持的相对重要性，我们实验地在宿主castaneum及其天然微孢子虫Nosema whitei之间进行了拮抗共同进化。我们的研究结果表明，与寄生虫的共同进化确实抵消了漂变，因为共同进化的种群具有显著更高的杂合性和等位基因多样性。遗传漂变仍然是一种强大的力量，在小群体中大大减少了遗传变异，增加了遗传分化。令我们惊讶的是，当它们与寄生虫共同进化时，进化种群之间的差异较小，这表明平行平衡选择。因此，我们的结果在实验上证明了霍尔丹最初的假设在其提出60年后是正确的。
Genetic variation in natural populations is a prime prerequisite allowing populations to respond to selection, but is under constant threat from forces that tend to reduce it, such as genetic drift and many types of selection. Haldane emphasized the potential importance of parasites as a driving force of genetic diversity. His theory has been taken for granted ever since, but despite numerous studies showing correlations between genetic diversity and parasitism, Haldane's hypothesis has rarely been tested experimentally for unambiguous support. We experimentally staged antagonistic coevolution between the host Tribolium castaneum and its natural microsporidian parasite, Nosema whitei, to test for the relative importance of two separate evolutionary forces (drift and parasite-induced selection) on the maintenance of genetic variation. Our results demonstrate that coevolution with parasites indeed counteracts drift as coevolving populations had significantly higher levels of heterozygosity and allelic diversity. Genetic drift remained a strong force, strongly reducing genetic variation and increasing genetic differentiation in small populations. To our surprise, differentiation between the evolving populations was smaller when they coevolved with parasites, suggesting parallel balancing selection. Hence, our results experimentally vindicate Haldane's original hypothesis 60 years after its conception.