Local adaptation is commonly cited to explain species distribution, but how fitness varies along continuous geographical gradients is not well understood. Here, we combine thermal biology and life-history theory to demonstrate that Drosophila populations along a 2500 km latitudinal cline are adapted to local conditions. We measured how heat tolerance and viability rate across eight populations varied with temperature in the laboratory and then simulated their expected cumulative Darwinian fitness employing high-resolution temperature data from their eight collection sites. Simulations indicate a trade-off between annual survival and cumulative viability, as both mortality and the recruitment of new flies are predicted to increase in warmer regions. Importantly, populations are locally adapted and exhibit the optimal combination of both traits to maximize fitness where they live. In conclusion, our method is able to reconstruct fitness surfaces employing empirical life-history estimates and reconstructs peaks representing locally adapted populations, allowing us to study geographic adaptation in silico.

中文翻译：

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果蝇沿纬度梯度的适应表面和局部热适应

局部适应通常被用来解释物种分布，但适应性如何沿着连续的地理梯度变化尚不清楚。在这里，我们将热生物学和生活史理论结合起来，证明沿 2500 公里纬度斜坡的果蝇种群适应了当地条件。我们在实验室中测量了八个种群的耐热性和生存率如何随温度变化，然后利用来自八个采集点的高分辨率温度数据模拟了它们的预期累积达尔文适应性。模拟表明，年存活率和累积生存力之间存在权衡，因为预计在较温暖的地区，死亡率和新果蝇的招募都会增加。重要的是，种群适应当地环境，并表现出两种特征的最佳组合，以最大限度地提高其居住地的适应性。总之，我们的方法能够利用经验生活史估计来重建适应度表面，并重建代表当地适应人群的峰值，使我们能够在计算机中研究地理适应。