Department of Biology, College of Arts and Sciences, Emory University, Atlanta, GA 30322, USA.
Population Biology, Ecology, and Evolution Graduate Program, Laney Graduate School, Emory University, Atlanta, GA 30322, USA.
Biol Lett. 2020 Jan;16(1):20190744. doi: 10.1098/rsbl.2019.0744. Epub 2020 Jan 29.
Parasites often infect genetically diverse host populations, and the evolutionary trajectories of parasite populations may be shaped by levels of host heterogeneity. Mixed genotype host populations, compared to homogeneous host populations, can reduce parasite prevalence and potentially reduce rates of parasite adaptation due to trade-offs associated with adapting to specific host genotypes. Here, we used experimental evolution to select for increased virulence in populations of the bacterial parasite exposed to either heterogeneous or homogeneous populations of . We found that parasites exposed to heterogeneous host populations evolved significantly less virulence than parasites exposed to homogeneous host populations over several hundred bacterial generations. Thus, host heterogeneity impeded parasite adaptation to host populations. While we detected trade-offs in virulence evolution, parasite adaptation to two specific host genotypes also resulted in modestly increased virulence against the reciprocal host genotypes. These results suggest that parasite adaptation to heterogeneous host populations may be impeded by both trade-offs and a reduction in the efficacy of selection as different host genotypes exert different selective pressures on a parasite population.
寄生虫通常感染遗传多样性丰富的宿主群体，而寄生虫种群的进化轨迹可能受到宿主异质性水平的影响。与同质宿主群体相比，混合基因型宿主群体可以降低寄生虫的流行率，并可能由于与适应特定宿主基因型相关的权衡而降低寄生虫的适应速度。在这里，我们使用实验进化来选择对暴露于异质或同质宿主群体的细菌寄生虫 的毒力增加。我们发现，与暴露于同质宿主群体的寄生虫相比，暴露于异质宿主群体的寄生虫在数百代细菌中进化出的毒力显著降低。因此，宿主异质性阻碍了寄生虫对宿主群体的适应。虽然我们检测到了在毒力进化方面的权衡，但寄生虫对两种特定宿主基因型的适应也导致了对互惠宿主基因型的毒力适度增加。这些结果表明，寄生虫对异质宿主群体的适应可能受到权衡和选择有效性降低的阻碍，因为不同的宿主基因型对寄生虫种群施加不同的选择压力。
