BACKGROUND Many organisms are responding to climate change with dramatic range shifts, involving plastic and genetic changes to cope with novel climate regimes found at higher latitudes. Using experimental lineages of the seed beetle Callosobruchus maculatus, we simulated the initial phase of colonisation to progressively cooler and/or more variable conditions, to investigate how adaptation and phenotypic plasticity contribute to shifts in thermal tolerance during colonisation of novel climates. RESULTS We show that heat and cold tolerance rapidly evolve during the initial stages of adaptation to progressively cooler and more variable climates. The evolved shift in cold tolerance is, however, associated with maladaptive plasticity under the novel conditions, resulting in a pattern of countergradient variation between the ancestral and novel, fluctuating thermal environment. In contrast, lineages exposed to progressively cooler, but constant, temperatures over several generations expressed only beneficial plasticity in cold tolerances and no evolved response. CONCLUSIONS We propose that thermal adaptation during a range expansion to novel, more variable climates found at high latitudes and elevations may typically involve genetic compensation arising from maladaptive plasticity in the initial stages of adaptation, and that this form of (countergradient) thermal adaptation may represent an opportunity for more rapid and labile evolutionary change in thermal tolerances than via classic genetic assimilation models for thermal tolerance evolution (i.e., selection on existing reaction norms). Moreover, countergradient variation in thermal tolerances may typically mask cryptic genetic variability for these traits, resulting in apparent evolutionary stasis in thermal traits.

中文翻译：

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适应性差的可塑性促进了在实验范围变化期间热耐受性的发展。

背景技术许多生物正在以巨大的范围变化来应对气候变化，涉及塑性和遗传变化以应对在较高纬度处发现的新颖的气候状况。使用种子甲虫Callosobruchus maculatus的实验谱系，我们模拟了定殖到逐渐凉爽和/或更可变的条件的初始阶段，以研究适应性和表型可塑性如何在新型气候定殖过程中促进热耐受性的变化。结果我们显示，在适应逐渐凉爽和变化多端的气候的初始阶段，耐热和耐冷性迅速发展。但是，在新条件下，耐寒性的变化与适应不良的可塑性有关，从而导致祖先和新事物之间出现反梯度变化的模式，不断变化的热环境。相反，世代暴露于几代人逐渐降低但恒定的温度下，仅表现出有益的可塑性，具有耐寒性，而没有进化反应。结论我们提出，在适应范围扩大到在高纬度和高海拔地区发现的新型，多变气候的过程中，热适应通常可能涉及在适应初期由适应不良的塑性产生的遗传补偿，这种形式的（逆梯度）热适应可以代表与通过经典的遗传同化模型进行热耐受性进化（即根据现有反应规范进行选择）相比，热耐受性有更快，更不稳定的进化变化的机会。此外，