Rebolledo Adriana P, Sgrò Carla M, Monro Keyne
School of Biological Sciences, Monash University, Melbourne, VIC, Australia.
Front Physiol. 2021 Oct 20;12:738338. doi: 10.3389/fphys.2021.738338. eCollection 2021.
Understanding links between thermal performance and environmental variation is necessary to predict organismal responses to climate change, and remains an ongoing challenge for ectotherms with complex life cycles. Distinct life stages can differ in thermal sensitivity, experience different environmental conditions as development unfolds, and, because stages are by nature interdependent, environmental effects can carry over from one stage to affect performance at others. Thermal performance may therefore respond to carryover effects of prior thermal environments, yet detailed insights into the nature, strength, and direction of those responses are still lacking. Here, in an aquatic ectotherm whose early planktonic stages (gametes, embryos, and larvae) govern adult abundances and dynamics, we explore the effects of prior thermal environments at fertilization and embryogenesis on thermal performance curves at the end of planktonic development. We factorially manipulate temperatures at fertilization and embryogenesis, then, for each combination of prior temperatures, measure thermal performance curves for survival of planktonic development (end of the larval stage) throughout the performance range. By combining generalized linear mixed modeling with parametric bootstrapping, we formally estimate and compare curve descriptors (thermal optima, limits, and breadth) among prior environments, and reveal carryover effects of temperature at embryogenesis, but not fertilization, on thermal optima at completion of development. Specifically, thermal optima shifted to track temperature during embryogenesis, while thermal limits and breadth remained unchanged. Our results argue that key aspects of thermal performance are shaped by prior thermal environment in early life, warranting further investigation of the possible mechanisms underpinning that response, and closer consideration of thermal carryover effects when predicting organismal responses to climate change.
了解热性能与环境变化之间的联系对于预测生物体对气候变化的反应至关重要，对于具有复杂生命周期的变温动物来说，这仍然是一个持续存在的挑战。不同的生命阶段在热敏感性上可能存在差异，随着发育的进行会经历不同的环境条件，而且由于各阶段本质上相互依存，环境影响可能会从一个阶段延续到其他阶段从而影响其性能。因此，热性能可能会对先前热环境的遗留效应做出反应，但对于这些反应的性质、强度和方向仍缺乏详细的见解。在此，我们以一种水生变温动物为例，其早期浮游阶段（配子、胚胎和幼虫）决定成年个体的数量和动态，我们探究受精和胚胎发育阶段的先前热环境对浮游发育末期热性能曲线的影响。我们对受精和胚胎发育阶段的温度进行析因操纵，然后针对每种先前温度的组合，在整个性能范围内测量浮游发育（幼虫阶段末期）存活的热性能曲线。通过将广义线性混合模型与参数自抽样相结合，我们正式估计并比较先前环境之间的曲线描述符（热最适温度、极限温度和热幅），并揭示胚胎发育阶段而非受精阶段的温度遗留效应会对发育完成时的热最适温度产生影响。具体而言，热最适温度在胚胎发育过程中会随着温度变化而移动，而热极限温度和热幅则保持不变。我们的结果表明，热性能的关键方面在生命早期会受到先前热环境的影响，这值得进一步研究支撑该反应的可能机制，并在预测生物体对气候变化的反应时更密切地考虑热遗留效应。
