Climate warming is increasingly exposing wildlife to sublethal high temperatures, which may lead to chronic impacts and reduced fitness. Telomere length (TL) may link heat exposure to fitness, particularly at early-life stages, because developing organisms are especially vulnerable to adverse conditions, adversity can shorten telomeres, and TL predicts fitness. Here, we quantify how climatic and environmental conditions during early life are associated with TL in nestlings of wild purple-crowned fairy-wrens (Malurus coronatus), endangered songbirds of the monsoonal tropics. We found that higher average maximum air temperature (range 31 to 45 °C) during the nestling period was associated with shorter early-life TL. This effect was mitigated by water availability (i.e., during the wet season, with rainfall), but independent of other pertinent environmental conditions, implicating a direct effect of heat exposure. Models incorporating existing information that shorter early-life TL predicts shorter lifespan and reduced fitness showed that shorter TL under projected warming scenarios could lead to population decline across plausible future water availability scenarios. However, if TL is assumed to be an adaptive trait, population viability could be maintained through evolution. These results are concerning because the capacity to change breeding phenology to coincide with increased water availability appears limited, and the evolutionary potential of TL is unknown. Thus, sublethal climate warming effects early in life may have repercussions beyond individual fitness, extending to population persistence. Incorporating the delayed reproductive costs associated with sublethal heat exposure early in life is necessary for understanding future population dynamics with climate change.

中文翻译：

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炎热和干燥的条件预示着濒临灭绝的鸣禽的雏鸟端粒较短：对种群持久性的影响。

气候变暖使野生动物越来越多地暴露在亚致死高温下，这可能导致慢性影响和适应性下降。端粒长度 (TL) 可能将热暴露与健康联系起来，特别是在生命早期阶段，因为发育中的生物体特别容易受到不利条件的影响，逆境会缩短端粒，而 TL 可以预测健康。在这里，我们量化了生命早期的气候和环境条件如何与野生紫冠仙女鹪鹩 (Malurus coronatus) 的雏鸟中的 TL 相关，后者是季风热带地区的濒危鸣禽。我们发现，雏鸟期较高的平均最高气温（范围 31 至 45 °C）与较短的生命早期 TL 相关。这种影响被可用水（即在雨季降雨）减轻了，但独立于其他相关环境条件，暗示热暴露的直接影响。包含较短生命早期 TL 预测较短寿命和降低适应性的现有信息的模型表明，在预测的变暖情景下较短的 TL 可能导致未来可能的可用水情景中的人口下降。然而，如果假设 TL 是一种适应性特征，则可以通过进化维持种群生存能力。这些结果令人担忧，因为改变育种物候以适应增加的可用水量的能力似乎有限，而且 TL 的进化潜力未知。因此，生命早期的亚致死气候变暖效应可能会产生超出个体适应性的影响，并扩展到种群持久性。