Data from: Too hot to die? The effects of vegetation shading on past, present, and future activity budgets of two diurnal skinks from arid Australia

Behavioral thermoregulation is an important mechanism allowing ectotherms to respond to thermal variations. Its efficiency might become imperative for securing activity budgets under future climate change. For diurnal lizards, thermal microhabitat variability appears to be of high importance, especially in hot deserts where vegetation is highly scattered and sensitive to climatic fluctuations. We investigated the effects of a shading gradient from vegetation on body temperatures and activity timing for two diurnal, terrestrial desert lizards, Ctenotus regius, and Morethia boulengeri, and analyzed their changes under past, present, and future climatic conditions. Both species’ body temperatures and activity timing strongly depended on the shading gradient provided by vegetation heterogeneity. At high temperatures, shaded locations provided cooling temperatures and increased diurnal activity. Conversely, bushes also buffered cold temperature by saving heat. According to future climate change scenarios, cooler microhabitats might become beneficial to warm-adapted species, such as C. regius, by increasing the duration of daily activity. Contrarily, warmer microhabitats might become unsuitable for less warm-adapted species such as M. boulengeri for which midsummers might result in a complete restriction of activity irrespective of vegetation. However, total annual activity would still increase provided that individuals would be able to shift their seasonal timing towards spring and autumn. Overall, we highlight the critical importance of thermoregulatory behavior to buffer temperatures and its dependence on vegetation heterogeneity. Whereas studies often neglect ecological processes when anticipating species’ responses to future climate change the strongest impact of a changing climate on terrestrial ectotherms in hot deserts is likely to be the loss of shaded microhabitats rather than the rise in temperature itself. We argue that conservation strategies aiming at addressing future climate changes should focus more on the cascading effects of vegetation rather than on shifts of species distributions predicted solely by climatic envelopes.

行为性体温调节（behavioral thermoregulation）是变温动物（ectotherms）应对温度波动的重要机制。在未来气候变化背景下，其调控效率对保障动物的活动时间分配至关重要。对于日行性蜥蜴而言，微生境温度异质性尤为关键，尤其是在植被高度分散且对气候波动敏感的炎热沙漠中。本研究针对两种日行性陆生沙漠蜥蜴——红纹栉眼蜥（Ctenotus regius）与布氏石龙子（Morethia boulengeri），探究了植被遮荫梯度对其体温与活动节律的影响，并分析了过去、当前与未来气候条件下的相关变化。两种蜥蜴的体温与活动节律均显著依赖于植被异质性所形成的遮荫梯度。在高温环境中，遮荫区域可起到降温作用并延长日间活动时长；反之，灌丛亦可通过蓄热缓解低温胁迫。根据未来气候变化情景，对于暖适应物种如红纹栉眼蜥而言，凉爽微生境可通过延长其每日活动时长而成为有利条件。与之相反，温暖微生境或将不再适配弱暖适应物种如布氏石龙子：无论植被覆盖情况如何，仲夏时节其活动可能完全受限。不过，若个体能够将季节活动节律向春季与秋季偏移，其全年总活动时长仍可实现提升。总体而言，本研究凸显了体温调节行为在缓冲温度波动中的关键作用，以及其对植被异质性的依赖关系。当前多数研究在预测物种对未来气候变化的响应时，往往忽略了生态过程；而炎热沙漠中的陆生变温动物所受气候变化的最强影响，大概率是遮荫微生境的丧失，而非气温本身的升高。我们认为，旨在应对未来气候变化的保护策略，应更多关注植被的级联效应，而非仅基于气候包络模型（climatic envelopes）预测的物种分布偏移。