Mountain ranges harbour exceptionally high biodiversity, which is now under threat from rapid environmental change. However, despite decades of effort, the limited availability of data and analytical tools has prevented a robust and truly global characterization of elevational biodiversity gradients and their evolutionary origins. This has hampered a general understanding of the processes involved in the assembly and maintenance of montane communities. Here we show that a worldwide mid-elevation peak in bird richness is driven by wide-ranging species and disappears when we use a subsampling procedure that ensures even species representation in space and facilitates evolutionary interpretation. Instead, richness corrected for range size declines linearly with increasing elevation. We find that the more depauperate assemblages at higher elevations are characterized by higher rates of diversification across all mountain regions, rejecting the idea that lower recent diversification rates are the general cause of less diverse biota. Across all elevations, assemblages on mountains with high rates of past temperature change exhibit more rapid diversification, highlighting the importance of climatic fluctuations in driving the evolutionary dynamics of mountain biodiversity. While different geomorphological and climatic attributes of mountain regions have been pivotal in determining the remarkable richness gradients observed today, our results underscore the role of ongoing and often very recent diversification processes in maintaining the unique and highly adapted biodiversity of higher elevations.

中文翻译：

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全球海拔多样性和鸟类多样化

山脉拥有极高的生物多样性，现在正受到快速环境变化的威胁。然而，尽管进行了数十年的努力，但数据和分析工具的有限可用性阻碍了对海拔生物多样性梯度及其进化起源的可靠和真正的全球表征。这阻碍了对山地社区组装和维护过程的一般理解。在这里，我们表明，鸟类丰富度的全球中海拔峰值是由范围广泛的物种驱动的，当我们使用子采样程序确保物种在空间中的均匀代表性并促进进化解释时，该峰值就会消失。相反，根据范围大小校正的丰富度随着海拔的增加而线性下降。我们发现，海拔越高越贫瘠的组合的特征是所有山区的多样化率越高，拒绝最近较低的多样化率是生物群多样性减少的一般原因的观点。在所有海拔高度，过去温度变化率高的山脉上的组合表现出更快速的多样化，突出了气候波动在推动山区生物多样性进化动态方面的重要性。虽然山区的不同地貌和气候属性对于确定今天观察到的显着丰富度梯度至关重要，但我们的结果强调了持续的和通常是最近的多样化过程在维持高海拔独特和高度适应的生物多样性方面的作用。