Data from: The plastic fly: the effect of sustained fluctuations in adult food supply on life history traits

Many adult traits in Drosophila melanogaster show phenotypic plasticity, and the effects of diet on traits such as lifespan and reproduction are well explored. Although plasticity in response to food is still present in older flies, it is unknown how sustained environmental variation affects life-history traits. Here, we explore how such life-long fluctuations of food supply affect weight and survival in groups of flies and affect weight, survival and reproduction in individual flies. In both experiments, we kept adults on constant high or low food and compared these to flies that experienced fluctuations of food either once or twice a week. For these ‘yoyo’ groups, the initial food level and the duration of the dietary variation differed during adulthood, creating four ‘yoyo’ fly groups. In groups of flies, survival and weight were affected by adult food. However, for individuals, survival and reproduction, but not weight, were affected by adult food, indicating that single and group housing of female flies affects life-history trajectories. Remarkably, both the manner and extent to which life-history traits varied in relation to food depended on whether flies initially experienced high or low food after eclosion. We therefore conclude that the expression of life-history traits in adult life is affected not only by adult plasticity, but also by early adult life experiences. This is an important but often overlooked factor in studies of life-history evolution and may explain variation in life-history experiments.

黑腹果蝇（Drosophila melanogaster）的诸多成体性状均表现出表型可塑性（phenotypic plasticity），饮食对寿命、繁殖等性状的影响已得到充分研究。尽管老龄果蝇仍保留对食物的可塑性响应，但持续的环境变化如何作用于其生活史性状（life-history traits），目前仍无定论。本研究旨在探究食物供应的终生波动如何影响果蝇群体的体重与存活情况，以及个体果蝇的体重、存活与繁殖能力。在两项实验中，我们将成体果蝇分别饲养于恒定高、低食物环境中，并与每周经历1次或2次食物波动的果蝇组进行对照。针对这类“悠悠球”饮食组，我们在成虫期设置了初始食物水平与饮食变化时长的差异，最终构建出4个“悠悠球”果蝇组。果蝇群体实验结果显示，成体食物条件会显著影响群体的存活与体重。但针对个体果蝇的实验则表明，成体食物条件仅影响其存活与繁殖能力，而非体重，这提示雌果蝇的单只饲养与群体饲养模式，会改变其生活史轨迹。尤为值得关注的是，生活史性状随食物条件变化的方式与幅度，均取决于果蝇羽化（eclosion）后的初始食物环境。据此我们得出结论：成体生活史性状的表达，不仅受成体阶段的可塑性调控，还受到成虫早期经历的影响。这一关键因素在生活史进化研究中常被忽视，或可解释现有生活史实验中的结果异质性。