Global warming is predicted to increase both average temperatures and the frequency and duration of heat waves. Tropical ectotherms, particularly those living in warm environments are more prone to receive heat impacts. Then, it is crucial to identify those populations already exposed to high temperatures that may be at risk of decimation by ongoing warming. We assessed heating risk in a population of the fish species Astyanax bimaculatus, inhabiting hot pools in intermittent streams in the Brazilian Caatinga ecoregion. We experimentally examined the upper thermal tolerance (CT_max), and provided estimates of warming tolerance (WT), as the difference between CT_max and micro-environmental peak temperatures (T_max). Two CT_max estimates ranged between 37.6 and 40.6°C, whereas pond T_max ranged between 34.6 and 41.3°C. This determines very narrow, even negative WTs, for these extreme heated A. bimaculatus populations, which ultimately may determine their local extinction in the coming decades.

中文翻译：

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巴西卡廷加鱼 Astyanax bimaculatus (Linnaeus, 1758) 种群的耐热性上限和对全球变暖的脆弱性

预计全球变暖会增加平均温度以及热浪的频率和持续时间。热带变温动物，尤其是那些生活在温暖环境中的动物，更容易受到热影响。然后，至关重要的是确定那些已经暴露在高温下的人群，这些人群可能会因持续变暖而面临灭绝的风险。我们评估了居住在巴西卡廷加生态区间歇性溪流热水池中的双斑双斑鱼（ Astyanax bimaculatus ）种群的加热风险。我们通过实验检查了耐热性上限 (CT _{max )，并提供了对变暖耐受性 (WT) 的估计，作为 CT max}和微环境峰值温度 ( T _max )之间的差异。两台CT_最大估计值介于 37.6 和 40.6°C 之间，而池塘T_最大值介于 34.6 和 41.3°C 之间。这决定了这些极端加热的A. bimaculatus种群的非常狭窄甚至负的 WT，这最终可能决定它们在未来几十年内的局部灭绝。