Data from: Adaptation to fluctuating environments in a selection experiment with Drosophila melanogaster

A fundamental question in life-history evolution is how organisms cope with fluctuating environments, including variation between stressful and benign conditions. For short-lived organisms, environments commonly vary between generations. Using a novel experimental design, we exposed wild-derived Drosophila melanogaster to three different selection regimes: one where generations alternated between starvation and benign conditions, and starvation was always preceded by early exposure to cold; another where starvation and benign conditions alternated in the same way, but cold shock sometimes preceded starvation and sometimes benign conditions; and a third where conditions were always benign. Using six replicate populations per selection regime, we found that selected flies increased their starvation resistance, most strongly for the regime where cold and starvation were reliably combined, and this occurred without decreased fecundity or extended developmental time. The selected flies became stress resistant, displayed a pronounced increase in early-life food intake and resource storage. In contrast to previous experiments selecting for increased starvation resistance in D. melanogaster, we did not find increased storage of lipids as the main response, but instead that, in particular for females, storage of carbohydrates was more pronounced. We argue that faster mobilization of carbohydrates is advantageous in fluctuating environments and conclude that the phenotype that evolved in our experiment corresponds to a compromise between the requirements of stressful and benign environments.

生活史演化领域的一个核心问题，在于生物体如何应对波动环境——包括胁迫环境与适宜环境之间的变化。对于短命生物而言，环境变化通常发生在代际之间。我们采用新颖的实验设计，将野生来源的黑腹果蝇（Drosophila melanogaster）置于三种不同的选择处理（selection regime）下：其一为代际交替经历饥饿与适宜条件，且饥饿事件始终伴随早期低温暴露；其二同样以相同模式交替出现饥饿与适宜条件，但冷激处理有时会先于饥饿事件，有时则先于适宜条件；其三则始终维持适宜环境。我们为每种选择处理设置6个重复种群，结果显示经选择的果蝇饥饿抗性显著提升，其中以低温与饥饿可靠配对的处理组提升效果最为显著，且该性状演化并未伴随繁殖力下降或发育时长延长。经选择的果蝇获得了胁迫抗性，其早期食物摄入与资源储存量均出现显著提升。与此前在黑腹果蝇中筛选提高饥饿抗性的实验不同，本研究并未发现脂质储存增加作为主要响应表型，反而尤其在雌性个体中，碳水化合物储存的提升更为显著。我们认为，碳水化合物的快速动员在波动环境中具有适应性优势，并由此推断，本实验中演化出的表型对应了胁迫环境与适宜环境需求之间的权衡。