Data from: Multiple dimensions of bird beta diversity support that mountains are higher in the tropics

Aim We examine latitudinal effects of breeding bird taxonomic,
phylogenetic and functional β-diversity (Tβ, Pβ and Fβ, respectively)
along elevational gradients to test predictions derived from Janzen’s
(1967) classic ideas that tropical mountains represent stronger dispersal
barriers than temperate mountains. Location Global Taxon Birds Methods
Using a global dataset from 46 mountains, we examine latitudinal patterns
of Tβ, Pβ, and Fβ, and their components: β rich and β repl. For each
mountain and each dimension of diversity we calculated (a) total
β-diversity, (b) the steepness of distance decay patterns, and (c)
within-mountain variability in pairwise β-diversity and regressed each one
of these response variables against absolute latitude. We predicted that
tropical montane biotas would have (1) overall higher Tβ, Pβ, and Fβ, (2)
faster distance decay patterns and (3) higher within-mountain variability
in pairwise β-diversity. Furthermore, we expected the richness component β
rich to be more important in temperate mountains, and the replacement
component β repl in tropical mountains. Results Latitude had a negative
effect on total β-diversity for all dimensions of diversity. Similarly,
metrics of Tβ and Pβ mostly agree with our expectations, whereas Fβ showed
contrasting results with steeper distance decay curves and higher
within-mountain variability in temperate mountains. Overall, β rich was a
more important component at high elevations in the tropics and across
elevations in temperate mountains, and β repl more important in tropical
low and mid-elevations. Main Conclusions Our findings are consistent with
tropical mountain assemblages containing species with narrow elevational
distributions, low dispersal ability and potentially high allopatric
speciation, resulting in high β-diversity across elevations. Contrasting
results for Fβ indicate high niche packing in tropical assemblages, with
most changes in functional diversity among assemblages involving species
redundant in trait space. --

目的 我们沿海拔梯度考察繁殖鸟类分类、系统发育及功能β多样性（分别为Tβ、Pβ和Fβ）的纬度效应，以验证基于Janzen（1967）经典观点的预测——热带山地相较于温带山地构成更强的扩散屏障。地点 全球 类群 鸟类 方法 利用来自46座山地的全球数据集，我们分析了Tβ、Pβ和Fβ的纬度格局及其组分：β丰富度（β rich）和β替换度（β repl）。针对每座山地及每个多样性维度，我们计算了（a）总β多样性、（b）距离衰减格局的陡峭度、（c）山内成对β多样性的变异性，并将这些响应变量分别与绝对纬度进行回归分析。我们预测热带山地生物群将具有（1）整体更高的Tβ、Pβ和Fβ；（2）更快的距离衰减格局；（3）山内成对β多样性更高的变异性。此外，我们预期丰富度组分β rich在温带山地更重要，而替换度组分β repl在热带山地更重要。结果 纬度对所有多样性维度的总β多样性均存在负效应。类似地，Tβ和Pβ的度量指标大多与我们的预期一致，而Fβ则呈现相反结果——温带山地的距离衰减曲线更陡峭且山内变异性更高。总体而言，β rich在热带高海拔及温带各海拔区域是更重要的组分，而β repl在热带低海拔和中海拔区域更重要。主要结论 我们的研究结果与热带山地群落包含海拔分布狭窄、扩散能力低且潜在异域物种形成率高的物种这一特征一致，从而导致跨海拔的高β多样性。Fβ的相反结果表明热带群落存在高生态位填充，群落间功能多样性的大多数变化涉及性状空间冗余的物种。