Department of Biology, Georgetown University, Washington, DC, United States of America.
PLoS One. 2019 Sep 5;14(9):e0222227. doi: 10.1371/journal.pone.0222227. eCollection 2019.
Organisms from temperate ecosystems experience a cyclic alternation of favorable seasons, when they can grow and develop, and unfavorable periods, characterized by low temperatures and reduced resource availability. A common adaptation to these changing conditions is to undergo a state of metabolic arrest triggered by environmental cues (e.g. diapause) during the unfavorable periods. Altered environmental conditions resulting from global change can expose organisms to contradictory cues, potentially triggering maladaptive responses. Here, I compared the performance of an oligophagous butterfly when experiencing consistent vs contradictory environmental cues by manipulating temperature, daylength, and host plant in the laboratory. I implemented a fully factorial design with realistic temperature and photoperiodic regimes to resemble environmental conditions during mid-summer and the summer-autumn transition within the focal species' range. To assess the role of host plant at mediating the effects of abiotic factors, larvae were fed foliage of either a high or a low-quality host species. Decreasing daylength was the primary cue inducing diapause; however, feeding on a low-quality host at low temperatures also induced diapause in larvae growing under constant summer daylength. Conversely, exposure to high temperatures while feeding on a high-quality host occasionally overruled the diapause-inducing effect of decreasing daylength. Feeding on a high-quality host mitigated the lethal effects of cold, but not of hot temperatures. In addition, exposure to cold temperatures resulted in a significant reduction of pupal mass only under decreasing daylength. These results indicate that responses to environmental stressors in this multivoltine butterfly differ across the growing season according to the eco-physiological state of individuals (whether they undergo direct development or diapause). Traits related to oligophagy, such as sensitivity to multiple cues for diapause induction, as well as some of its consequences, such as the occurrence of overlapping generations, are likely to mitigate some of the detrimental effects of global change.
温带生态系统中的生物经历着有利季节和不利季节的周期性交替，在有利季节它们可以生长和发育，而在不利季节则受到低温和资源减少的限制。一种常见的适应策略是在不利时期，根据环境线索（如休眠）进入代谢停滞状态。全球变化导致的环境条件变化可能会使生物面临相互矛盾的线索，从而引发适应不良的反应。在这里，我通过在实验室中操纵温度、日照长度和宿主植物，比较了一种寡食性蝴蝶在经历一致和矛盾的环境线索时的表现。我采用了真实的温度和光周期模式的完全因子设计，以模拟研究物种范围内仲夏和夏秋季过渡期间的环境条件。为了评估宿主植物在调节非生物因素影响中的作用，幼虫被喂食高或低质量的宿主植物叶片。缩短日照长度是诱导休眠的主要线索；然而，在恒定的夏季日照长度下，幼虫在低温下以低质量的宿主为食也会诱导休眠。相反，在喂食高质量宿主的同时暴露于高温环境偶尔会推翻日照长度降低引起休眠的效果。以高质量的宿主为食减轻了低温的致死效应，但不能减轻高温的致死效应。此外，只有在日照长度缩短的情况下，暴露于低温环境才会显著降低蛹重。这些结果表明，这种多化性蝴蝶对环境胁迫的反应在生长季节根据个体的生态生理状态（它们是否经历直接发育或休眠）而不同。与寡食性相关的特征，如对多种休眠诱导线索的敏感性，以及其一些后果，如重叠世代的发生，可能会减轻一些全球变化的不利影响。
