Data from: Fitness costs of rapid cold-hardening in Ceratitis capitata

Rapid cold-hardening (RCH) is a unique form of phenotypic plasticity which confers survival advantages at low temperature. The fitness costs of RCH are generally poorly elucidated and are important to understanding the evolution of plastic physiology. This study examined whether RCH responses, induced by ecologically relevant diel temperature fluctuations, carry metabolic, survival or fecundity costs. We predicted that potential costs in RCH would be manifested as differences in metabolic rate, fecundity or survival in flies which have hardened versus those which have not, or flies which have experienced more RCH events would show greater costs than those which have experienced fewer events. One group of flies cooled to 10°C for 2h for 11 consecutive days experienced daily RCH (Hardened), whilst the other group exposed to 15°C for the same 2h period each day formed a Control group. Hardened flies had higher survival at -5°C for 2h than control flies (69±9% vs. 44±19%, P=0.04). Hardened flies showed no metabolic or fecundity costs, but had reduced average survival (P=0.0403). Thus, a major cost to repeated low temperature exposures in C. capitata is through direct mortality caused by chilling injury, although this appears not to be a direct cost of RCH.快速冷驯化（Rapid cold-hardening, RCH）是一种独特的表型可塑性形式，可赋予生物体在低温环境下的生存优势。目前学界对快速冷驯化的适合度代价尚未充分阐明，而这一问题对于理解可塑性生理的演化进程至关重要。本研究探讨了由生态相关的昼夜温度波动诱导的快速冷驯化响应是否会带来代谢、存活或繁殖适合度代价。我们预测，快速冷驯化的潜在代价将表现为两类差异：一是经历冷驯化与未经历冷驯化的实蝇之间在代谢速率、繁殖力或存活率上的差异；二是经历更多次冷驯化事件的实蝇比经历较少次数的实蝇表现出更显著的代价。实验中将实蝇分为两组：一组连续11天每天在10℃环境中冷却2小时，每日经历快速冷驯化，记为驯化组；另一组每天在相同的2小时时段内置于15℃环境中，作为对照组。驯化组实蝇在-5℃环境中暴露2小时的存活率显著高于对照组（69±9% vs. 44±19%，P=0.04）。驯化组实蝇未表现出代谢或繁殖适合度代价，但平均存活率有所降低（P=0.0403）。因此，对于地中海实蝇（C. capitata）而言，反复暴露于低温环境的主要代价来自冷损伤引发的直接死亡，尽管这似乎并非快速冷驯化本身的直接代价。