The processes responsible for the formation of Earth’s most conspicuous diversity pattern, the latitudinal diversity gradient (LDG), remain unexplored for many clades in the Tree of Life. Here, we present a densely sampled and dated molecular phylogeny for the most speciose clade of damselflies worldwide (Odonata: Coenagrionoidea) and investigate the role of time, macroevolutionary processes, and biome-shift dynamics in shaping the LDG in this ancient insect superfamily. We used process-based biogeographic models to jointly infer ancestral ranges and speciation times and to characterize within-biome dispersal and biome-shift dynamics across the cosmopolitan distribution of Coenagrionoidea. We also investigated temporal and biome-dependent variation in diversification rates. Our results uncover a tropical origin of pond damselflies and featherlegs ~105 Ma, while highlighting the uncertainty of ancestral ranges within the tropics in deep time. Even though diversification rates have declined since the origin of this clade, global climate change and biome-shifts have slowly increased diversity in warm- and cold-temperate areas, where lineage turnover rates have been relatively higher. This study underscores the importance of biogeographic origin and time to diversify as important drivers of the LDG in pond damselflies and their relatives, while diversification dynamics have instead resulted in the formation of ephemeral species in temperate regions. Biome-shifts, although limited by tropical niche conservatism, have been the main factor reducing the steepness of the LDG in the last 30 Myr. With ongoing climate change and increasing northward range expansions of many damselfly taxa, the LDG may become less pronounced. Our results support recent calls to unify biogeographic and macroevolutionary approaches to improve our understanding of how latitudinal diversity gradients are formed and why they vary across time and among taxa.

中文翻译：

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新的分子系统发育揭示了热带起源、全球多样化和池塘豆娘 （Coenagrionoidea） 中的扩散


导致地球最显著的多样性模式——纬度多样性梯度 （LDG） 形成的过程，在生命之树的许多分支中仍未得到探索。在这里，我们提出了全球最特殊的豆娘分支 （Odonata： Coenagrionoidea） 的密集采样和年代测定的分子系统发育，并研究了时间、宏观进化过程和生物群落变化动力学在塑造这个古老昆虫超科的 LDG 中的作用。我们使用基于过程的生物地理模型来共同推断祖先范围和物种形成时间，并表征 Coenagrionoidea 世界分布中的生物群落内扩散和生物群落转移动力学。我们还研究了多样化率的时间和生物群落依赖性变化。我们的结果揭示了池塘豆娘和羽腿鱼的热带起源 ~105 马，同时强调了热带地区祖先分布范围在深时内的不确定性。尽管自该分支起源以来，多样性率有所下降，但全球气候变化和生物群落变化缓慢增加了暖温带和寒温带地区的多样性，这些地区的谱系更替率相对较高。这项研究强调了生物地理起源和时间多样化的重要性，这是池塘豆娘及其亲缘种 LDG 的重要驱动因素，而多样化动态反而导致了温带地区短暂物种的形成。生物群落转移虽然受到热带生态位保守性的限制，但一直是降低过去 30 Myr 中 LDG 陡峭度的主要因素。随着持续的气候变化和许多豆娘类群向北扩展的范围，LDG 可能会变得不那么明显。 我们的结果支持了最近关于统一生物地理学和宏观进化方法的呼吁，以提高我们对纬度多样性梯度如何形成以及为什么它们随时间和分类群变化的理解。