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.

快速冷硬化（Rapid cold-hardening，简称RCH）是一种独特的表型塑性表现形式，能在低温环境下赋予生物生存优势。RCH的适应代价通常难以阐释，对于理解塑性生理学的进化具有重要意义。本研究旨在探讨由生态相关昼夜温度波动诱导的RCH反应是否会产生代谢、生存或繁殖的代价。我们预测，RCH潜在的代价将表现为硬化与未硬化的果蝇在代谢率、繁殖力或生存率方面的差异，或经历更多RCH事件的果蝇将展现出比经历较少事件者更大的代价。一组果蝇连续11天每天冷却至10°C，持续2小时，以经历每日的RCH（硬化组），而另一组每天在同一时间段暴露于15°C的果蝇则构成对照组。硬化果蝇在-5°C下持续2小时的生存率高于对照组（69±9% vs. 44±19%，P=0.04）。硬化果蝇未表现出代谢或繁殖代价，但平均生存率有所下降（P=0.0403）。因此，对于C. capitata而言，反复暴露于低温的主要代价是通过冷害导致的直接死亡率，尽管这并非RCH的直接代价。