Activity niches outperform thermal physiological limits in predicting global ant distributions

Aim: Thermal physiology is commonly used in mechanistic models to predict species distributions and project distribution change. Such thermal constraints for ants are often measured under laboratory conditions as critical thermal limits (CTmax and CTmin), but have also been observed in the field as foraging thermal limits (FTmin and FTmax). Here we compared distribution projections based on ant physiological and behavioural thermal limits with their realized distributions to assess the validity of using ecophysiological models to predict species ranges over large scales. Location: Global Taxon: Ants Methods: From published literature, we compiled a database of 148 lab-measured critical thermal limits and 137 field-observed foraging thermal limits for 20 ant genera distributed around the world. We projected their potential ranges using active hour thresholds by matching their thermal limits or preferred thermal breadth (incorporating thermal optima) with hourly surface temperature data. We then compared the projections against a comprehensive global database of ant distributions to assess the validity of physiologically and behaviorally based models. Results: We found that surface temperature plays a clear role in generic-level ant biogeography. Projections based on foraging thermal limits were more conservative in constraining ranges to observed distributions, while projections based on critical thermal limits often overestimated ranges. Furthermore, thermal limit models can be improved by incorporating behaviourally derived thermal optima. Main conclusions: Our results suggest that temperature-dependent activity niches and thermal optima better reveal species realized thermal niches than critical thermal limits, and hence can improve predictions of species distributions and future distribution changes under climate change.研究目的：热生理学常被应用于机制模型，以预测物种分布及分布变化趋势。针对蚂蚁的这类热限制条件，通常在实验室条件下以临界热极限（critical thermal limits，CTmax与CTmin）的形式进行测定，同时也可在野外被观测为觅食热极限（foraging thermal limits，FTmin与FTmax）。本研究对比了基于蚂蚁生理与行为热极限的分布预测结果与其实际分布范围，以评估利用生理生态学模型在大尺度下预测物种分布范围的有效性。 研究区域：全球范围 研究类群：蚂蚁（Ants） 研究方法：本研究从已发表文献中整理构建数据库，涵盖全球分布的20个蚂蚁属的148组实验室测定的临界热极限数据，以及137组野外观测得到的觅食热极限数据。我们通过将蚂蚁的热极限或偏好热广度（结合热最适值）与逐小时地表温度数据匹配，基于活动时长阈值预测其潜在分布范围。随后，将预测结果与全面的全球蚂蚁分布数据库进行对比，以评估基于生理与行为的模型的有效性。 研究结果：我们发现地表温度在属级蚂蚁生物地理学中具有明确作用。基于觅食热极限的分布预测在约束分布范围以匹配实际观测结果时更为保守，而基于临界热极限的预测则往往高估了分布范围。此外，纳入行为学推导得到的热最适值可优化热极限模型。 主要结论：本研究结果表明，相较于临界热极限，依赖温度的活动生态位与热最适值能够更好地反映物种的实际热生态位，因此可提升气候变化背景下物种分布及未来分布变化的预测精度。