In the study of factors shaping species' poleward range boundaries, climatic constraints are often assigned greater importance than biotic interactions such as competition. However, theory suggests competition can truncate a species' fundamental niche in harsh environments. We test this by challenging a mechanistic niche model – containing explicit competition terms – to predict the poleward range boundaries of two globally distributed, ecologically similar aquatic plant species. Mechanistic competition models accurately predicted the northern range limits of our study species, outperforming competition‐free mechanistic models and matching the predictive ability of statistical niche models fit to occurrence records. Using the framework of modern coexistence theory, we found that relative nonlinearity in competitors' responses to temperature fluctuations maintains their coexistence boundary, highlighting the importance of this fluctuation‐dependent mechanism. Our results support a more nuanced, interactive role of climate and competition in determining range boundaries, and illustrate a practical, process‐based approach to understanding the determinants of range limits.

中文翻译：

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共存壁垒限制了全球分布工厂的极地范围

在研究影响物种极地范围边界的因素时，气候限制通常比竞争性生物相互作用更为重要。但是，理论表明，竞争可以在恶劣的环境中截断物种的基本利基。我们通过挑战一种机制利基模型（包含明确的竞争条件）来测试这一点，以预测两种全球分布，生态相似的水生植物物种的极地范围边界。机械竞争模型能够准确预测我们研究物种的北限，优于无竞争机制模型，并使统计利基模型的预测能力与发生记录相匹配。使用现代共存理论的框架，我们发现竞争者的相对非线性 对温度波动的响应保持了它们的共存边界，突出了这种依赖于波动的机制的重要性。我们的结果支持气候和竞争在确定范围边界时发挥更细微的互动作用，并说明了一种实用的基于过程的方法来了解范围限制的决定因素。