Data from: Divergence of gastropod life history in contrasting thermal environments in a geothermal lake

Experiments using natural populations have provided mixed support for thermal adaptation models, probably because the conditions are often confounded with additional environmental factors like seasonality. The contrasting geothermal environments within Lake Mývatn, northern Iceland, provide a unique opportunity to evaluate thermal adaptation models using closely located natural populations. We conducted laboratory common garden and field reciprocal transplant experiments to investigate how thermal origin influences the life history of Radix balthica snails originating from stable cold (6 °C), stable warm (23 °C) thermal environments or from areas with seasonal temperature variation. Supporting thermal optimality models, warm origin snails survived poorly at 6 °C in the common garden experiment and better than cold origin and seasonal snails in the warm habitat in the reciprocal transplant experiment. Contrary to thermal adaptation models, growth rate in both experiments was highest in the warm populations irrespective of temperature, indicating cogradient variation. The optimal temperatures for growth and reproduction were similar irrespective of origin, but cold origin snails always had the lowest performance, and seasonal origin snails often performed at an intermediate level compared to snails originating in either stable environment. Our results indicate that central life-history traits can differ in their mode of evolution, with survival following the predictions of thermal optimality models, whereas ecological constraints have shaped the evolution of growth rates in local populations.利用自然种群开展的实验对热适应模型的支持结果并不一致，这可能是因为实验条件常与季节性等额外环境因素相混淆。冰岛北部米湖（Lake Mývatn）内反差显著的地热环境，为利用地理位置相近的自然种群评估热适应模型提供了独特契机。本研究开展了实验室共同花园实验与野外互惠移植实验，以探究热起源如何影响巴氏萝卜螺（Radix balthica）的生活史特征，这些螺类分别源自稳定低温（6 ℃）、稳定高温（23 ℃）环境，或是具有季节性温度波动的区域。实验结果支持热最优模型：在共同花园实验中，源自高温环境的螺类在6 ℃条件下存活率极低；而在互惠移植实验的高温生境中，其存活率高于源自低温环境与季节性波动环境的螺类。但与热适应模型相悖的是，在两个实验中，源自高温种群的螺类生长速率均为最高，且不受实验温度影响，这表明存在协同梯度变异。不同热起源螺类的生长与繁殖最适温度并无显著差异，但源自低温环境的螺类始终表现最差，而源自季节性波动环境的螺类的表现通常介于两类稳定环境来源的螺类之间。本研究结果表明，核心生活史特征的进化模式存在差异：存活率符合热最优模型的预测，而生态约束塑造了局域种群生长速率的进化历程。