Hutter Carl R, Lambert Shea M, Wiens John J
Am Nat. 2017 Dec;190(6):828-843. doi: 10.1086/694319. Epub 2017 Oct 23.
The Tropical Andes make up Earth's most species-rich biodiversity hotspot for both animals and plants. Nevertheless, the ecological and evolutionary processes underlying this extraordinary richness remain uncertain. Here, we examine the processes that generate high richness in the Tropical Andes relative to other regions in South America and across different elevations within the Andes, using frogs as a model system. We combine distributional data, a newly generated time-calibrated phylogeny for 2,318 frog species, and phylogenetic comparative methods to test the relative importance of diversification rates and colonization times for explaining Andean diversity at different scales. At larger scales (among regions and families), we find that faster diversification rates in Andean clades most likely explain high Andean richness. In contrast, at smaller temporal and spatial scales (within family-level clades within the Andes), diversification rates rarely explain richness patterns. Instead, we show that colonization times are important for shaping elevational richness patterns within the Andes, with more species found in habitats colonized earlier. We suggest that these scale-dependent patterns might apply to many other richness gradients. Recognition of this scale dependence may help to reconcile conflicting results among studies of richness patterns across habitats, regions, and organisms.
热带安第斯山脉是地球上动植物种类最为丰富的生物多样性热点地区。然而，这种非凡丰富性背后的生态和进化过程仍不明确。在这里，我们以蛙类作为模型系统，研究相对于南美洲其他地区以及安第斯山脉不同海拔而言，热带安第斯山脉产生高物种丰富度的过程。我们结合分布数据、一个新生成的涵盖2318种蛙类物种的时间校准系统发育树以及系统发育比较方法，来检验物种形成速率和定殖时间对于解释不同尺度下安第斯山脉生物多样性的相对重要性。在较大尺度（区域和科之间），我们发现安第斯分支中更快的物种形成速率最有可能解释安第斯山脉的高物种丰富度。相比之下，在较小的时间和空间尺度（安第斯山脉内科级分支内部），物种形成速率很少能解释丰富度模式。相反，我们表明定殖时间对于塑造安第斯山脉内的海拔丰富度模式很重要，在更早定殖的栖息地发现了更多物种。我们认为这些依赖尺度的模式可能适用于许多其他丰富度梯度。认识到这种尺度依赖性可能有助于调和不同栖息地、区域和生物体丰富度模式研究之间相互矛盾的结果。
