Salazar et al. 2024_EJLS

The Andes, with its diverse topography and climate, is a renowned cradle for adaptive radiation, particularly for vertebrate ectotherms like lizards. Yet, the role of temperature in promoting physiological specialization in the Andes remains unclear. Aseasonality in the tropics should favor physiological specialization across elevation in lizards, but empirical data are limited and equivocal. Determining how thermal tolerances are geographically and phylogenetically structured, therefore, is a priority, particularly as environments continue to rapidly change. However, there's a gap in our knowledge of thermal limits of species from the Andes, one of the planet’s most biodiverse regions. Anoles, a diverse lizard group found across thousands of meters of elevation in the Andes, can offer insights into evolutionary adaptations to temperature. This study focused on 14 anole species from two different anole clades (Dactyloa and Draconura) that independently diversified along elevational gradients in the Andes. We measured critical thermal limits (CT_min and CT_max) and found patterns of thermal tolerance specialization across altitude, both among and within species. Patterns of thermal specialization are similar among anole clades, indicating parallel responses to similar environmental pressures. Specifically, high-elevation anoles tolerate colder temperature and are less heat tolerant than their low elevation counterparts, rendering thermal tolerance breadths stable across elevation (thermal specialization). Evolutionary rates of physiological traits were similar, reflecting parallel specialization in heat and cold tolerance across elevation. The adaptive radiation of anole lizards reflects physiological specialization across elevation, and the endemism such specialization favors likely catalyzed their remarkable diversity in the tropical Andes.

安第斯山脉地形与气候多样，是适应性辐射的著名摇篮，尤其对蜥蜴等脊椎动物变温动物而言。然而，温度在促进安第斯山脉生物生理特化中的作用仍不明确。热带地区的无季节性本应有利于蜥蜴跨海拔的生理特化，但实证数据有限且结论不一。因此，确定热耐受性的地理与系统发育结构是当务之急，尤其是在环境持续快速变化的背景下。然而，对于地球上生物多样性最丰富的区域之一——安第斯山脉物种的热极限，我们的认知仍存在空白。安乐蜥（Anoles）是安第斯山脉跨数千米海拔分布的多样化蜥蜴类群，可为温度适应性进化研究提供洞见。本研究聚焦于安第斯山脉沿海拔梯度独立分化的两个安乐蜥支系（Dactyloa与Draconura）中的14个物种。我们测定了临界热极限（CT_min与CT_max），发现跨海拔的热耐受性特化模式存在于物种间及物种内。安乐蜥各支系的热特化模式相似，表明它们对相似环境压力存在平行响应。具体而言，高海拔安乐蜥比低海拔同类更耐受低温，但耐热性更弱，使得热耐受宽度在跨海拔范围内保持稳定（即热特化）。生理性状的进化速率相似，反映出跨海拔的耐热与耐寒特化具有平行性。安乐蜥的适应性辐射体现了跨海拔的生理特化，而这种特化所促成的特有性很可能推动了其在热带安第斯山脉的显著多样性。