Gotcha N, Terblanche J S, Nyamukondiwa C
Department of Biological Sciences and Biotechnology Sciences, Botswana International University of Science and Technology (BIUST), Palapye, Botswana.
Department of Conservation Ecology and Entomology, Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa.
J Evol Biol. 2018 Jan;31(1):98-110. doi: 10.1111/jeb.13201. Epub 2017 Nov 16.
Plastic adjustments of physiological tolerance to a particular stressor can result in fitness benefits for resistance that might manifest not only in that same environment but also be advantageous when faced with alternative environmental stressors, a phenomenon termed 'cross-tolerance'. The nature and magnitude of cross-tolerance responses can provide important insights into the underlying genetic architecture, potential constraints on or versatility of an organism's stress responses. In this study, we tested for cross-tolerance to a suite of abiotic factors that likely contribute to setting insect population dynamics and geographic range limits: heat, cold, desiccation and starvation resistance in adult Ceratitis rosa following acclimation to all these isolated individual conditions prior to stress assays. Traits of stress resistance scored included critical thermal (activity) limits, chill coma recovery time (CCRT), heat knockdown time (HKDT), desiccation and starvation resistance. In agreement with other studies, we found that acclimation to one stress typically increased resistance for that same stress experienced later in life. A more novel outcome, however, is that here we also found substantial evidence for cross-tolerance. For example, we found an improvement in heat tolerance (critical thermal maxima, CT ) following starvation or desiccation hardening and improved desiccation resistance following cold acclimation, indicating pronounced cross-tolerance to these environmental stressors for the traits examined. We also found that two different traits of the same stress resistance differed in their responsiveness to the same stress conditions (e.g. HKDT was less cross-resistant than CT ). The results of this study have two major implications that are of broader importance: (i) that these traits likely co-evolved to cope with diverse or simultaneous stressors, and (ii) that a set of common underlying physiological mechanisms might exist between apparently divergent stress responses in this species. This species may prove to be a valuable model for future work on the evolutionary and mechanistic basis of cross-tolerance.
对特定应激源的生理耐受性的可塑性调整可带来抗性方面的适应性益处，这种益处不仅可能在相同环境中显现，而且在面对其他环境应激源时也具有优势，这一现象被称为“交叉耐受性”。交叉耐受性反应的性质和程度可为潜在的遗传结构、生物体应激反应的潜在限制或通用性提供重要见解。在本研究中，我们测试了成年蔷薇果实蝇对一系列非生物因素的交叉耐受性，这些因素可能有助于设定昆虫种群动态和地理分布范围限制：在应激试验前，让蔷薇果实蝇分别适应所有这些单独的条件后，测试其耐热性、耐寒性、抗干燥性和抗饥饿性。所记录的抗逆性状包括临界热（活动）极限、冷昏迷恢复时间（CCRT）、热击倒时间（HKDT）、抗干燥性和抗饥饿性。与其他研究一致，我们发现适应一种应激通常会增加对后期生活中经历的相同应激的抗性。然而，一个更新颖的结果是，我们在此还发现了大量交叉耐受性的证据。例如，我们发现饥饿或干燥预处理后耐热性（临界热最大值，CT）有所提高，冷适应后抗干燥性有所提高，这表明在所研究的性状中对这些环境应激源具有明显的交叉耐受性。我们还发现，同一抗逆性状的两个不同特征对相同应激条件的反应不同（例如，HKDT的交叉抗性低于CT）。本研究结果有两个更具广泛重要性的主要意义：（i）这些性状可能共同进化以应对多种或同时存在的应激源，（ii）在该物种明显不同的应激反应之间可能存在一组共同的潜在生理机制。该物种可能被证明是未来关于交叉耐受性的进化和机制基础研究的有价值模型。
