Data from: Global mammal betadiversity show parallel assemblage structure in similar but isolated environments

The taxonomic, phylogenetic and trait dimensions of betadiversity each provide unique insight into the importance of historical isolation and environmental conditions in shaping global diversity. These three dimensions should, in general, be positively correlated. However, if similar environmental conditions filter species with similar trait values, then assemblages located in similar environmental conditions, but separated by large dispersal barriers, may show high taxonomic, high phylogenetic, but low trait betadiversity. Conversely, we expect lower phylogenetic diversity but higher trait biodiversity among assemblages that are connected but are in differing environmental conditions. We calculated all pairwise comparisons of ~110x110 km grid-cells across the globe for ~5,000 mammal species (~70 million comparisons). We considered realms as units representing geographic distance and historical isolation and biomes as units with similar environmental conditions. While betadiversity dimensions were generally correlated, we highlight geographic regions of decoupling among betadiversity dimensions. Our analysis shows that assemblages from tropical forests in different realms had low trait dissimilarity while phylogenetic betadiversity was significantly higher than expected, suggesting potential convergent evolution. Low trait betadiversity was surprisingly not found between isolated deserts, despite harsh environmental conditions. Overall, our results provide evidence for parallel assemblage structure of mammal assemblages driven by environmental conditions at a global scale.

β多样性（betadiversity）的分类学、系统发育与功能性状（trait）三个维度，各自能够为揭示历史隔离与环境条件在塑造全球物种多样性过程中的重要作用提供独特视角。通常而言，这三个维度应呈现正相关关系。然而，若相似的环境条件会筛选具有相似功能性状值的物种，则处于相似环境条件但被大型扩散屏障分隔的物种群落，可能表现出较高的分类学β多样性与系统发育β多样性，但功能性状β多样性却较低。反之，对于彼此连通但所处环境条件存在差异的物种群落，我们预期其系统发育多样性更低，而功能性状生物多样性更高。
我们针对全球范围内约5000种哺乳动物，对所有约110×110千米的网格单元开展两两比对，总计完成约7000万次比对。我们将生物地理界视为表征地理距离与历史隔离的单元，将生物群系视为代表相似环境条件的单元。尽管β多样性的各维度总体上呈现相关性，但我们重点揭示了不同β多样性维度之间出现解耦的地理区域。
我们的分析显示，不同生物地理界内的热带森林群落，其功能性状相异度较低，但系统发育β多样性显著高于预期，这暗示了潜在的趋同演化现象。尽管沙漠环境条件严苛，但令人意外的是，彼此隔离的沙漠群落之间并未表现出较低的功能性状β多样性。总体而言，我们的研究结果为全球尺度下由环境条件驱动的哺乳动物群落平行结构提供了实证支撑。