Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
EPFL, Department of Systems Biology, Lausanne, Switzerland.
Mol Biol Evol. 2021 Jun 25;38(7):2732-2749. doi: 10.1093/molbev/msab061.
Periods of nutrient shortage impose strong selection on animal populations. Experimental studies of genetic adaptation to nutrient shortage largely focus on resistance to acute starvation at adult stage; it is not clear how conclusions drawn from these studies extrapolate to other forms of nutritional stress. We studied the genomic signature of adaptation to chronic juvenile malnutrition in six populations of Drosophila melanogaster evolved for 150 generations on an extremely nutrient-poor larval diet. Comparison with control populations evolved on standard food revealed repeatable genomic differentiation between the two set of population, involving >3,000 candidate SNPs forming >100 independently evolving clusters. The candidate genomic regions were enriched in genes implicated in hormone, carbohydrate, and lipid metabolism, including some with known effects on fitness-related life-history traits. Rather than being close to fixation, a substantial fraction of candidate SNPs segregated at intermediate allele frequencies in all malnutrition-adapted populations. This, together with patterns of among-population variation in allele frequencies and estimates of Tajima's D, suggests that the poor diet results in balancing selection on some genomic regions. Our candidate genes for tolerance to larval malnutrition showed a high overlap with genes previously implicated in acute starvation resistance. However, adaptation to larval malnutrition in our study was associated with reduced tolerance to acute adult starvation. Thus, rather than reflecting synergy, the shared genomic architecture appears to mediate an evolutionary trade-off between tolerances to these two forms of nutritional stress.
营养短缺时期会对动物种群造成强烈的选择压力。对营养短缺条件下遗传适应性的实验研究主要集中在成年期对急性饥饿的抵抗上；目前尚不清楚这些研究的结论如何外推到其他形式的营养压力。我们研究了 6 个黑腹果蝇种群在极度缺乏营养的幼虫饮食上经过 150 代进化后对慢性青少年营养不良的适应的基因组特征。与在标准食物上进化的对照组种群进行比较，发现两组种群之间存在可重复的基因组分化，涉及超过 3000 个候选单核苷酸多态性（SNP），形成超过 100 个独立进化的聚类。候选基因组区域富含与激素、碳水化合物和脂质代谢相关的基因，其中一些基因与与适应度相关的生活史特征有关。候选 SNP 并没有接近固定，而是在所有适应营养不良的种群中以中等等位基因频率分离。这一点，加上等位基因频率的种群间变异模式和 Tajima 的 D 的估计，表明在一些基因组区域，不良饮食导致了平衡选择。我们对幼虫营养不良的耐受性的候选基因与先前与急性饥饿抵抗有关的基因有很高的重叠。然而，在我们的研究中，对幼虫营养不良的适应与对急性成年饥饿的耐受性降低有关。因此，这种共享的基因组结构似乎不是协同作用的反映，而是介导了对这两种营养压力形式的耐受性之间的进化权衡。
