The relationship between chill-coma onset and recovery at the extremes of the thermal window of Drosophila melanogaster.

Critical thermal minimum (CT(min)), a measure of chill-coma onset temperature, and chill-coma recovery (CCR), the time taken to recover from chill coma, are common metrics of thermal tolerance in insects. We investigated the relationship between CT(min) and CCR in a single population of adult Drosophila melanogaster exposed to a range of rearing (14°, 21.5°, and 27°C), acclimation (5 d at 6° or 29°C), and hardening (1 h at 0° or 36°C) conditions. CT(min) ranged from -4.2° to 8.8°C and CCR from 12.1 to 55.1 min, and CT(min) and CCR varied in the same direction: populations with low CT(min) tended to have short CCR. Acclimation had a greater effect on CT(min) and CCR than short-term hardening. There was a significant positive rank correlation between CT(min) and CCR, but the relationship was demonstrably curvilinear, suggesting that although plasticity in these measures is correlated through the central part of the relationship, there is no relationship between CT(min) and CCR across a range of values generated by phenotypic plasticity. This implies that the mechanisms underlying plasticity in CT(min) are not entirely shared with those underlying CCR.