Evolution of Drosophila resistance against different pathogens and infection routes entails no detectable maintenance costs
Evolution of Drosophila resistance against different pathogens and infection routes entails no detectable maintenance costs
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DOI：
10.1111/evo.12782
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发表时间：
2015-11-01
期刊：
影响因子：
3.3
通讯作者：
Magalhaes, Sara
中科院分区：
文献类型：
--
作者：
Faria, Vitor G.;Martins, Nelson E.;Magalhaes, Sara
病原体对宿主施加强大的选择压力，使宿主适应感染。这种适应往往会对其他与健康相关的性状产生负面影响。这种权衡可能是维持遗传多样性以抵抗病原体的基础。权衡可以用适应寄生虫的宿主种群的实验进化来测试，使用两种方法：（1）测量放松选择系中免疫活性的变化;（2）比较进化系和对照系在无病原体环境中的生活史性状。在这里，我们使用这两种方法来检查果蝇种群进化超过30代的果蝇C病毒或细菌嗜虫假单胞菌，后者通过不同的途径感染下的权衡。我们发现，抗性保持30代后放松选择。此外，在无病原体的环境中，即使在干旱、营养限制和高密度等压力下，控制和进化种群之间的几个经典生活史特征也没有差异。因此，我们没有检测到与病原体抗性相关的任何维护成本。我们假设，通常使用的极高的选择压力，导致不成比例的表达成本相对于它们在自然系统中的实际发生。尽管如此，维持病原体抗性的遗传变异需要一个解释。
Pathogens exert a strong selective pressure on hosts, entailing host adaptation to infection. This adaptation often affects negatively other fitness-related traits. Such trade-offs may underlie the maintenance of genetic diversity for pathogen resistance. Trade-offs can be tested with experimental evolution of host populations adapting to parasites, using two approaches: (1) measuring changes in immunocompetence in relaxed-selection lines and (2) comparing life-history traits of evolved and control lines in pathogen-free environments. Here, we used both approaches to examine trade-offs in Drosophila melanogaster populations evolving for over 30 generations under infection with Drosophila C Virus or the bacterium Pseudomonas entomophila, the latter through different routes. We find that resistance is maintained after up to 30 generations of relaxed selection. Moreover, no differences in several classical life-history traits between control and evolved populations were found in pathogen-free environments, even under stresses such as desiccation, nutrient limitation, and high densities. Hence, we did not detect any maintenance costs associated with resistance to pathogens. We hypothesize that extremely high selection pressures commonly used lead to the disproportionate expression of costs relative to their actual occurrence in natural systems. Still, the maintenance of genetic variation for pathogen resistance calls for an explanation.