Department of Ecology and Evolutionary Biology, School of Biological Sciences, University of California, Irvine, California, United States of America.
PLoS One. 2020 Oct 2;15(10):e0240132. doi: 10.1371/journal.pone.0240132. eCollection 2020.
Our intuitive understanding of adaptation by natural selection is dominated by the power of selection at early ages in large populations. Yet, as the forces of natural selection fall with adult age, we expect adaptation to be attenuated with age. Explicit simulations of age-dependent adaptation suggest that populations adapt to a novel environment quickly at early ages, but only slowly and incompletely at later adult ages. Experimental tests for age-dependent adaptation to a novel diet were performed on populations of Drosophila melanogaster. The results support the prediction that populations should perform better on an ancestral, long-abandoned diet, compared to an evolutionarily recent diet, only at later ages. D. melanogaster populations also perform poorly on a novel diet compared to an evolutionarily recent diet that has been sustained for hundreds of generations, particularly at earlier ages. Additional experiments demonstrate that the timing of the shift to better performance in our populations on the long-abandoned diet is dependent on when the forces of natural selection weaken in the evolutionary history of experimental populations. Taken together, these experimental findings suggest that the forces of natural selection scale the rate of adaptation to novel environments.
我们对自然选择适应性的直观理解主要受早期大群体中选择力量的影响。然而，随着成年年龄的增长，自然选择的力量减弱，我们预计适应性也会随着年龄的增长而减弱。对年龄相关适应性的明确模拟表明，在早期，种群可以快速适应新环境，但在后期成年阶段，适应性只能缓慢且不完全。对黑腹果蝇种群进行了适应新饮食的年龄依赖性实验测试。结果支持了这样的预测，即在后期，与进化上最近的饮食相比，种群在祖先、长期废弃的饮食上的表现应该更好。与已经持续了数百代的进化上最近的饮食相比，黑腹果蝇种群在新饮食上的表现也很差，尤其是在早期。此外的实验表明，在我们的种群中，向长期废弃的饮食更好表现的转变时间取决于实验种群进化史中自然选择力量减弱的时间。总之，这些实验结果表明，自然选择的力量调节了对新环境的适应速度。
