J. B. S. Haldane is widely quoted to have quipped that the Creator, if one exists, has an inordinate fondness for beetles. Although Coleoptera may not be the most speciose order once Hymenopteran diversity is fully accounted for, as a whole the very clear differences in species diversity among taxa require an explanation. Here we use stochastic simulations to show that dispersal has eco‐evolutionary effects that predict taxa to become particularly species‐rich when dispersal is neither too low nor too high. Our model combines recent advances in understanding coexistence in niche space with previously verbally expressed ideas, where too low dispersal imposes biogeographic constraints that prevent a lineage from finding new areas to colonize (reducing opportunities for speciation), while too high dispersal impedes population divergence, leading to few but widely distributed species. We show that this logic holds for species richness and is robust to a variety of model assumptions, but peak diversification rate is instead predicted to increase with dispersal. Our work unifies findings of increasing and decreasing effects of dispersal rate on speciation, and explains why taxa with moderate dispersal abilities have the best prospects for high global species richness.

中文翻译：

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对具有中等分散能力的物种的偏爱

众所周知，JBS Haldane曾开玩笑说，造物主（如果存在）对甲虫有过分的爱好。尽管一旦充分考虑了膜翅目的多样性，鞘翅目可能并不是最特殊的顺序，但总体而言，分类单元之间物种多样性的非常明显的差异需要解释。在这里，我们使用随机模拟表明，扩散具有生态进化效应，可以预测当扩散既不是太低又不是太高时，分类群变得特别丰富。我们的模型将了解小众空间共存方面的最新进展与以前的口头表达相结合，分散度太低会限制生物地理学的限制，从而阻止沿袭找到新的殖民地（减少物种形成的机会），而分散度太高则会阻碍人口的分化，导致数量极少但分布广泛的物种。我们表明，这种逻辑适用于物种丰富度，并且对各种模型假设均具有鲁棒性，但预测峰的分散速率反而会随着分散而增加。我们的工作统一了扩散速率对物种形成影响增加和降低的发现，并解释了为什么具有中等扩散能力的生物分类群具有全球物种丰富度最高的最佳前景。