Species' range edges are expanding to both warmer and cooler regions. Yet, no studies directly compared the changes in range-limiting traits within the same species during both types of range expansions. To increase our mechanistic understanding of range expansions it is crucial to disentangle the contributions of plastic and genetic changes in these traits. The aim of this study was to test for plastic and evolutionary changes in heat tolerance, life history and behaviour, and compare these during range expansions toward warmer and cooler regions. Using laboratory experiments we reconstructed the thermal performance curves (TPCurves) of larval life history (survival, growth and development rates) and larval heat tolerance (CTmax) across two recent range expansions from the core populations in southern France toward a warmer (southeastern Spain) and a cooler (northwestern Spain) region in Europe by the damselfly Ischnura elegans. First-generation larvae from field-collected mothers were reared across a range of temperatures (16 - 28 °C) in incubators. The range expansion to the warmer region was associated with the evolution of a greater ability to cope with high temperatures (increased mean and thermal plasticity of CTmax), faster development and partly a faster growth indicating a higher time constraints caused by a shorter time frame available for larval development associated with a transition to a greater voltinism. Our results thereby support the emerging pattern that plasticity in heat tolerance alone is inadequate to adapt to new thermal regimes. The range expansion to the cooler region was associated with faster growth indicating countergradient variation without a change in CTmax. The evolution of a faster growth rate during both range expansions could be explained by a greater digestive efficiency rather than an increased food intake. Our results highlight that range expansions to warmer and cooler regions can result in similar evolutionary changes in the TPCurves for life history, and no opposite changes in heat tolerance.

中文翻译：

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在向温暖和寒冷地区扩张的过程中，生命史和耐热性的热演化

物种的范围边缘正在扩大到温暖和凉爽的地区。然而，没有研究直接比较在两种类型的范围扩展期间同一物种内范围限制性状的变化。为了增加我们对范围扩展的机制理解，解开这些性状中塑性和遗传变化的贡献至关重要。这项研究的目的是测试耐热性、生活史和行为方面的塑性和进化变化，并在向温暖和凉爽地区扩张的过程中比较这些变化。通过实验室实验，我们重建了幼虫生活史（存活、生长和发育率）和幼虫耐热性（CTmax）在最近两次从法国南部的核心种群扩展到欧洲较温暖（西班牙东南部）和欧洲较冷（西班牙西北部）地区的豆娘 Ischnura elegans。来自野外采集的母亲的第一代幼虫在孵化器中在一系列温度 (16 - 28 °C) 中饲养。向较温暖地区的范围扩展与应对高温的能力更强（CTmax 的平均值和热可塑性增加）、更快的发展和部分更快的增长有关，这表明由于可用的时间范围更短而导致的时间限制更大幼虫发育与过渡到更大的 voltinism 相关。因此，我们的结果支持新出现的模式，即单独的耐热塑性不足以适应新的热状态。向较冷区域的范围扩展与更快的增长相关，表明逆梯度变化而 CTmax 没有变化。在两次范围扩展期间，更快的增长率的演变可以通过更高的消化效率而不是食物摄入量的增加来解释。我们的结果强调，向温暖和凉爽地区的范围扩展会导致生命史的 TP 曲线发生类似的进化变化，并且耐热性没有相反的变化。在两次范围扩展期间，更快的增长率的演变可以通过更高的消化效率而不是食物摄入量的增加来解释。我们的结果强调，向温暖和凉爽地区的范围扩展会导致生命史的 TP 曲线发生类似的进化变化，并且耐热性没有相反的变化。在两次范围扩展期间，更快的增长率的演变可以通过更高的消化效率而不是食物摄入量的增加来解释。我们的结果强调，向温暖和凉爽地区的范围扩展会导致生命史的 TP 曲线发生类似的进化变化，并且耐热性没有相反的变化。