Data from: Thermal adaptation of cellular membranes in natural populations of Drosophila melanogaster

1. Changes in temperature disrupt the fluidity of cellular membranes, which can negatively impact membrane integrity and cellular processes. Many ectotherms, including Drosophila melanogaster (Meigen), adjust the glycerophospholipid composition of their membranes to restore optimal fluidity when temperatures change, a type of trait plasticity termed homeoviscous adaptation. 2. Existing data suggest that plasticity in the relative abundances of the glycerophospholipids phosphatidylethanolamine (PE) and phosphatidylcholine (PC) underlies cellular adaptation to temporal variability in the thermal environment. For example, laboratory populations of D. melanogaster evolved in the presence of temporally variable temperatures have greater developmental plasticity of the ratio of PE to PC (PE/PC) and greater fecundity than do populations evolved at constant temperatures. 3. Here, we extend this work to natural populations of D. melanogaster by evaluating thermal plasticity of glycerophospholipid composition at different life stages, in genotypes isolated from Vermont, Indiana and North Carolina, USA. We also quantify the covariance between developmental and adult (reversible) plasticity, and between adult responses of the membrane to cool and warm thermal shifts. 4. As predicted by physiological models of homeoviscous adaptation, flies from all populations decrease PE/PC and the degree of lipid unsaturation in response to warm temperatures. Furthermore, these populations have diverged in their degree of membrane plasticity. Flies from the most variable thermal environment (Vermont, USA) decrease PE/PC to a greater extent than do other populations when developed at a warm temperature, a pattern that matches our previous observation in laboratory-evolved populations. We also find that developmental plasticity and adult plasticity of PE/PC covary across genotypes, but that adult responses to cool and warm thermal shifts do not. 5. When combined with our previous observations of laboratory-evolved populations, our findings implicate developmental plasticity of PE/PC as a mechanism of thermal adaptation in temporally variable environments. While little is known about the genetic bases of plastic responses to temperature, our observations suggest that both environmentally sensitive and environmentally specific alleles contribute to thermal adaptation of membranes, and that costs of plasticity may arise when the adult environment differs from that experienced during development.1. 温度变化会破坏细胞膜的流动性，进而对膜完整性及细胞过程产生负面影响。许多外温动物（ectotherms），包括黑腹果蝇（Drosophila melanogaster，Meigen），会在温度改变时调整细胞膜的甘油磷脂（glycerophospholipid）组成，以恢复最优流动性，这类性状可塑性被称为膜脂黏滞性自适应（homeoviscous adaptation）。 2. 现有数据表明，甘油磷脂中磷脂酰乙醇胺（phosphatidylethanolamine，PE）与磷脂酰胆碱（phosphatidylcholine，PC）的相对丰度可塑性，是细胞适应温度环境时间变异的基础。例如，在周期性变温环境中演化的黑腹果蝇实验室种群，其PE与PC的比值（PE/PC）具有更强的发育可塑性，且繁殖力高于在恒定温度下演化的种群。 3. 本研究将此类研究拓展至黑腹果蝇的自然种群，以美国佛蒙特州、印第安纳州及北卡罗来纳州分离得到的基因型为材料，评估其不同生命阶段的甘油磷脂组成热可塑性。此外，我们还量化了发育可塑性与成虫（可逆性）可塑性之间的协方差，以及成虫膜对降温与升温热转变的响应之间的协方差。 4. 正如膜脂黏滞性自适应的生理学模型所预测的那样，所有种群的果蝇在高温环境下均会降低PE/PC比值及脂类不饱和度。此外，这些种群的膜可塑性程度存在分化：在温度环境变异程度最高的美国佛蒙特州种群，其在高温环境下发育时，PE/PC比值的下降幅度高于其他种群，这一模式与我们此前在实验室演化种群中的观测结果一致。我们还发现，不同基因型的PE/PC发育可塑性与成虫可塑性之间存在协方差，但成虫对降温与升温热转变的响应之间并无协方差。 5. 结合此前针对实验室演化种群的观测结果，本研究表明PE/PC的发育可塑性是周期性变温环境中热适应的一种机制。尽管目前人们对温度响应可塑性的遗传基础所知甚少，但我们的观测结果显示，环境敏感型与环境特异性等位基因均参与了细胞膜的热适应，且当成虫所处环境与发育阶段所处环境不一致时，可能会产生可塑性成本。