Phenological shifts conserve thermal niches in North American birds and reshape expectations for climate-driven range shifts
Phenological shifts conserve thermal niches in North American birds and reshape expectations for climate-driven range shifts
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DOI：
10.1073/pnas.1705897114
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发表时间：
2017-11
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影响因子：
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通讯作者：
Jacob B. Socolar;Peter N. Epanchin;S. Beissinger;M. Tingley
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文献类型：
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作者：
Jacob B. Socolar;Peter N. Epanchin;S. Beissinger;M. Tingley
意义
气候变暖给鸟类带来两大挑战：面临更高的温度以及筑巢和资源出现时间同步性被打乱。为了应对，预计鸟类会通过迁移到更凉爽的地区来追踪温度，并通过更早繁殖来追踪资源出现时间。我们发现这两种反应是相互交织的。更早繁殖可以通过在关键的繁殖季节生命史事件期间降低温度来替代分布范围的改变。我们发现初夏温度影响北美鸟类的筑巢成功率，并且如今加利福尼亚的鸟类比一个世纪前大约早一周繁殖。因此，在没有地理迁移的情况下，鸟类现在筑巢时的温度与一个世纪前相似，这可能会重塑分布范围改变的需求和机会。
物种以两种主要方式应对气候变化：纬度或海拔上的分布范围改变以及生命史事件的物候变化。分布范围改变被广泛视为热生态位追踪的主要机制，鸟类和其他消费者的物候变化被广泛理解为追踪生物资源时间峰值的主要机制。然而，物候变化和分布范围改变各自同时为温度和资源追踪提供了机会，尽管物候变化在热生态位追踪中可能的作用被广泛忽视。
利用加利福尼亚鸟类调查的标准数据集以及一种基于可探测性的方法来量化物候信号，我们发现加利福尼亚鸟类群落在上个世纪将其繁殖物候提前了5 - 12天。这种物候变化可能追踪资源峰值的变化，但它也使筑巢期间的平均温度降低了1℃以上，大约与同期平均温度升高的幅度相同。我们进一步发现，在一个大陆尺度的鸟巢数据库中，初夏温度异常与筑巢成功率相关，这表明鸟类的热生态位可能广泛地受到筑巢期间温度的限制。
这些发现勾勒出一个适应面，在这个面上地理分布范围和繁殖物候共同对温度和资源物候所施加的限制做出反应。通过稳定筑巢期间的温度，物候变化可能减轻对分布范围改变的需求。全球变化生态学将受益于进一步探索物候调整作为热生态位追踪的一种潜在机制，反之亦然。
Significance Climate warming poses two major challenges for birds: exposure to higher temperatures and disruption of the synchrony between nesting and resource emergence. To cope, birds are expected to track temperature by moving to cooler areas and to track resource emergence by breeding earlier. We show that these two responses are intertwined. Earlier breeding can substitute for range shifts by reducing temperatures during critical breeding-season life-history events. We show that early-summer temperatures affect nesting success in North American birds and that Californian birds breed ∼1 wk earlier today than a century ago. Thus, without shifting geographically, birds now nest at similar temperatures as they did a century ago, which might reshape both the need and the opportunity for range shifts. Species respond to climate change in two dominant ways: range shifts in latitude or elevation and phenological shifts of life-history events. Range shifts are widely viewed as the principal mechanism for thermal niche tracking, and phenological shifts in birds and other consumers are widely understood as the principal mechanism for tracking temporal peaks in biotic resources. However, phenological and range shifts each present simultaneous opportunities for temperature and resource tracking, although the possible role for phenological shifts in thermal niche tracking has been widely overlooked. Using a canonical dataset of Californian bird surveys and a detectability-based approach for quantifying phenological signal, we show that Californian bird communities advanced their breeding phenology by 5–12 d over the last century. This phenological shift might track shifting resource peaks, but it also reduces average temperatures during nesting by over 1 °C, approximately the same magnitude that average temperatures have warmed over the same period. We further show that early-summer temperature anomalies are correlated with nest success in a continental-scale database of bird nests, suggesting avian thermal niches might be broadly limited by temperatures during nesting. These findings outline an adaptation surface where geographic range and breeding phenology respond jointly to constraints imposed by temperature and resource phenology. By stabilizing temperatures during nesting, phenological shifts might mitigate the need for range shifts. Global change ecology will benefit from further exploring phenological adjustment as a potential mechanism for thermal niche tracking and vice versa.