Plastic responses to four environmental stresses and cross‐resistance in a laboratory population of Drosophila melanogaster

Abstract

Summary1. Acclimation or hardening to one stress in arthropods can lead to a plastic response, which confers increased resistance to other stresses. Such cross‐resistance may indicate shared physiological resistance mechanisms and a possibility of joint evolution for resistance traits.2. In this study, we tested for cross‐resistance using Drosophila melanogaster as a model system. Adult females were assayed for resistance to cold, heat, desiccation and starvation following cold acclimation, heat hardening, desiccation hardening and starvation acclimation, resulting in 12 pretreatment‐by‐test combinations for estimating potential cross‐resistance effects. The acclimation/hardening regimes were chosen so that flies enhanced their resistance to the same type of stress as that used for the particular pretreatment.3. Two cases of cross‐resistance were found, with desiccation‐hardened and starvation‐acclimated flies being more resistant than control ones in heat and desiccation resistance tests, respectively. In four cases, no acclimation/hardening effect was observed, and for six pretreatment‐by‐test combinations, the effect of acclimation/hardening was negative.4. We also revealed that heat and desiccation hardening as well as acclimation to starvation had a cost under non‐stressful conditions leading to reduced longevity. Cold acclimation did not affect longevity, although its effect was difficult to estimate precisely: during pretreatment at a low temperature, biological ageing of the flies might be delayed.5. The pattern of acclimation/hardening responses considered in the context of literature data on stress resistance indicates that expression of heat‐shock proteins is not likely to contribute to the observed cross‐resistance, but other probable general stress resistance mechanisms such as reduction of metabolic rate and accumulation of energy reserves might be involved.6. The lack of cross‐resistance induced by acclimation/hardening treatments suggests that in an environment with multiple stresses, evolution of shared protective systems associated with plastic responses may be constrained.