Mountain's ecological and evolutionary variables

Aim. High levels of species richness in mountains are associated with their hypothetical roles as cradles and/or museums of diversity but the generality of these roles remains unknown. To fill this gap, we tested these two hypotheses at a global scale and assessed the direct and indirect effects of abiotic regional features on the variation of montane amphibian richness worldwide. Location. Global Time period: Last 300 million years Major taxa studied. Amphibians Methods. Using an amphibian phylogeny containing 7238 species, along with species distribution and climatic data, we estimated species richness, speciation rates, evolutionary time, terrain roughness, area, and climatic stability for 514 of the world's mountain ranges. Then, we evaluated the direct and indirect effects of these variables on richness patterns across these mountains using structural equation models. Results. We found that most diverse mountain ranges for amphibians are concentrated in the Neotropics, but the fastest speciation rates are not restricted to this region. Instead, we found that evolutionary time, area and climatic stability better explained the global patterns of amphibian diversity in mountains. Species richness is higher in mountain regions with large and climatically stable areas, where early derived lineages originated/established and accumulated through time. Main conclusions. Mountains host and invaluable biodiversity shaped through deep time. Differences in speciation rates do not play a major role in explaining amphibian species richness across mountains. Instead, mountains experiencing milder historical climatic oscillations and having greater available areas for species persistence likely faced lower extinction rates leading to an increased accumulation of amphibian species through time. This condition highlights the importance of mountains as museums of deep evolutionary legacies and speciose biotas研究目的：山地极高的物种丰富度常被认为与其作为多样性“摇篮”与/或“博物馆”的假说角色相关联，但这些角色的普遍性仍未明确。为填补这一研究空白，我们在全球尺度下检验了这两项假说，并评估了非生物区域特征对全球山地两栖动物丰富度变异的直接与间接影响。 研究区域：全球 时间跨度：近3亿年 研究类群：两栖动物 研究方法：我们采用包含7238个物种的两栖动物系统发育树（amphibian phylogeny），结合物种分布与气候数据，对全球514个山脉的物种丰富度、物种形成速率、演化时间、地形粗糙度、面积以及气候稳定性进行了估算。随后，我们通过结构方程模型（structural equation models）评估了上述变量对全球山脉物种丰富度格局的直接与间接影响。 研究结果：我们发现，两栖动物物种最丰富的山脉集中分布于新热带区（Neotropics），但最快的物种形成速率并未局限于该区域。进一步分析表明，演化时间、面积与气候稳定性更能解释全球山地两栖动物多样性的分布格局。在面积广阔且气候稳定的山地区域，早期分化的支系得以起源、定殖并随时间累积物种，因此这类区域的物种丰富度更高。 主要结论：山地孕育了极为珍贵的生物多样性，这些多样性经由漫长的地质时间塑造而成。物种形成速率的差异并非解释全球山地两栖动物丰富度格局的核心因素。相反，经历过较为温和的历史气候波动、且拥有充足栖息地面积以供物种存续的山地，其灭绝率更低，进而随时间累积了更多的两栖物种类群。这一发现凸显了山地作为深层演化遗产与物种丰富生物群落“博物馆”的重要价值。