AimUnderstanding the processes that structure biodiversity on Earth is a major challenge in biology. Our work tests three key hypotheses driving taxonomic changes in bird communities globally, focusing on nestedness and turnover components: (1) contemporary climate, related to energy and water availability; (2) climate stability, reflecting shifts since the last glacial maximum; and (3) climatic heterogeneity, describing environmental gradients. We also examine whether these processes explain deviations in phylogenetic composition from expectations based on taxonomic changes among communities.LocationGlobal.Time PeriodPresent.Major Taxa StudiedBirds.MethodsWe calculated total taxonomic dissimilarity, its nestedness and turnover components, between neighbouring cells considering all living bird species. We tested for significant phylogenetic over‐ and underdispersion by comparing observed phylogenetic dissimilarity to a null model. We used linear regression models to quantify the relationships between taxonomic dissimilarity and phylogenetic deviations with climatic variables representing our hypotheses.ResultsPrecipitation steepness, that is, relative changes in precipitation, was strongly correlated with taxonomic changes (R2 = 27%), driving both changes in local community richness (nestedness) and species replacement between different regional pools (turnover). These two processes were decoupled, with precipitation steepness driving richness differences up to 1200 mm of annual precipitation, and turnover being more relevant in hyperarid and tropical areas. Phylogenetic deviations were common (35% of global cells), resulting from both over‐ and underdispersion, but they lacked a climatic signal.Main ConclusionsOur work supports the hypothesis that climatic heterogeneity, due to precipitation steepness, is the main climatic factor driving composition changes in bird communities globally, controlling local richness and transitions between regional pools. Changes in species composition often lead to phylogenetic dispersion or clustering, but the main processes responsible for taxonomic sorting are phylogenetically neutral. As such, taxonomic and phylogenetic changes between neighbouring bird communities may be driven largely by different processes.

中文翻译：

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降水陡峭性驱动鸟类群落组成的全球变化模式，而没有主要的系统发育信号


Aim了解构建地球生物多样性的过程是生物学中的一个重大挑战。我们的工作检验了推动全球鸟类群落分类变化的三个关键假设，重点关注嵌套和周转组成部分：（1） 与能源和水的可用性有关的当代气候;（2） 气候稳定性，反映了自上次冰盛期以来的变化;（3） 气候异质性，描述环境梯度。我们还研究了这些过程是否解释了系统发育组成与基于群落之间分类变化的预期的偏差。位置Global.Time PeriodPresent.Major Taxa StudiedBirds.Methods我们计算了考虑所有现存鸟类的相邻细胞之间的总分类学差异性、嵌套性和周转成分。我们通过将观察到的系统发育差异与零模型进行比较来测试显着的系统发育过度离散和欠离散。我们使用线性回归模型来量化分类学差异和系统发育偏差之间的关系，气候变量代表我们的假设。结果降水陡峭度，即降水的相对变化，与分类变化 （R2 = 27%） 密切相关，驱动当地群落丰富度（嵌套度）的变化和不同区域池之间的物种更替（更替）。这两个过程是解耦的，降水陡峭性导致年降水丰富度差异高达 1200 毫米，而周转率在超干旱和热带地区更为相关。系统发育偏差很常见（占全球细胞的 35%），这是由过度分散和欠分散引起的，但它们缺乏气候信号。主要结论我们的工作支持这样一个假设，即由于降水陡峭而导致的气候异质性是驱动全球鸟类群落组成变化的主要气候因素，控制局部丰富度和区域池之间的过渡。物种组成的变化通常会导致系统发育分散或聚集，但负责分类学分选的主要过程在系统发育上是中性的。因此，邻近鸟类群落之间的分类学和系统发育变化可能在很大程度上是由不同的过程驱动的。