Data from: How bird clades diversify in response to climatic and geographic factors

While the environmental correlates of global patterns in standing species richness are well understood, it is poorly known which environmental factors promote diversification (speciation minus extinction) in clades. We tested several hypotheses for how geographic and climatic variables should affect diversification using a large dataset of bird sister genera endemic to the New World. We found support for the area, evolutionary speed, environmental predictability and climatic stability hypotheses, but productivity and topographic complexity were rejected as explanations. Genera that had accumulated more species tend to occupy wider niche space, manifested both as occurrence over wider areas and in more habitats. Genera with geographic ranges that have remained more stable in response to glacial-interglacial changes in climate were also more species rich. Since many relevant explanatory variables vary latitudinally, it is crucial to control for latitude when testing alternative mechanistic explanations for geographic variation in diversification among clades.

尽管全球现存物种丰富度格局的环境关联已被充分阐明，但目前仍不清楚哪些环境因子能够推动演化支（clade）内的分化速率（即物种形成速率减去灭绝速率）。本研究依托一套包含大量新大陆特有鸟类姊妹属的大型数据集，检验了地理与气候变量对分化速率的影响机制相关的多项假说。研究结果支持面积假说、演化速率假说、环境可预测性假说与气候稳定性假说，但未发现生产力与地形复杂度可作为分化速率的有效解释因子。物种积累更多的属往往占据更广阔的生态位空间，具体表现为分布范围更广、可利用的生境类型更多。在气候冰期-间冰期旋回中地理分布范围保持更稳定的属，其物种丰富度也更高。由于诸多相关解释变量均存在纬度梯度变化，因此在检验演化支间分化速率地理差异的不同机制解释时，对纬度变量进行控制至关重要。