MOTIVATION: Theory describing biodiversity gradients has focused on species richness with less conceptual synthesis outlining expectations for intraspecific diversity gradients, that is, broad‐scale population richness and genetic diversity. Consequently, there is a need for a diversity–gradient synthesis that complements species richness with population richness and genetic diversity. REVIEW METHODS: Species and population richness are the number of different species or populations in an area, respectively. Population richness can be totalled across species, within a species or averaged across species. Genetic diversity within populations can be summed or averaged across all species in an area or be averaged across an individual species. Using these definitions, we apply historical, ecological and evolutionary frameworks of species richness gradients to formulate predictions for intraspecific diversity gradients. REVIEW CONCLUSIONS: All frameworks suggest higher average population richness at high latitudes, but similar total population richness across latitudes. Predictions for genetic diversity patterns across species are not consistent across frameworks and latitudes. NEW ANALYSIS METHODS: Species range size tends to increase with latitude, so we used empirical data from c. 900 vertebrate species to test hypotheses relating species range size and richness to population richness and genetic diversity. NEW ANALYSIS CONCLUSIONS: Species range size was positively associated with its population richness but not with species‐specific genetic diversity. Furthermore, a positive linear relationship was supported between species richness and total population richness, but only weakly for average population richness. OVERALL CONCLUSION: Through the lens of species richness theories, our synthesis identifies an uncoupling between species richness, population richness and genetic diversity in many instances due to historical and contemporary factors. Range size and taxonomic differences appear to play a large role in moderating intraspecific diversity gradients. We encourage further analyses to jointly assess diversity–gradient theory at species, population and genetic levels towards better understanding Earth’s biodiversity distribution and refining biodiversity conservation.

中文翻译：

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三个层面的纬度生物多样性梯度：连接物种丰富度、种群丰富度和遗传多样性

动机：描述生物多样性梯度的理论侧重于物种丰富度，而较少的概念综合概述了对种内多样性梯度的期望，即广泛的种群丰富度和遗传多样性。因此，需要一种多样性梯度综合，用种群丰富度和遗传多样性来补充物种丰富度。审查方法：物种和种群丰富度分别是一个区域内不同物种或种群的数量。种群丰富度可以跨物种、物种内或跨物种平均。种群内的遗传多样性可以在一个地区的所有物种中求和或求平均值，或者在单个物种中求平均值。使用这些定义，我们应用历史，物种丰富度梯度的生态和进化框架，以制定对种内多样性梯度的预测。审查结论：所有框架都表明高纬度地区的平均人口丰富度较高，但跨纬度地区的总人口丰富度相似。对跨物种遗传多样性模式的预测在框架和纬度之间并不一致。新的分析方法：物种范围的大小往往随着纬度的增加而增加，因此我们使用了来自 c 的经验数据。900 种脊椎动物，用于测试将物种范围大小和丰富度与种群丰富度和遗传多样性相关联的假设。新的分析结论：物种范围大小与其种群丰富度呈正相关，但与物种特异性遗传多样性无关。此外，物种丰富度和总种群丰富度之间存在正线性关系，但仅对平均种群丰富度微弱。总体结论：通过物种丰富度理论的视角，我们的综合确定了由于历史和当代因素在许多情况下物种丰富度、种群丰富度和遗传多样性之间的脱节。范围大小和分类差异似乎在调节种内多样性梯度方面发挥着重要作用。我们鼓励进一步分析以在物种、种群和遗传水平上联合评估多样性梯度理论，以更好地了解地球的生物多样性分布并完善生物多样性保护。通过物种丰富度理论的视角，我们的综合确定了由于历史和当代因素在许多情况下物种丰富度、种群丰富度和遗传多样性之间的脱钩。范围大小和分类差异似乎在调节种内多样性梯度方面发挥着重要作用。我们鼓励进一步分析，在物种、种群和遗传水平上共同评估多样性梯度理论，以更好地了解地球的生物多样性分布并完善生物多样性保护。通过物种丰富度理论的视角，我们的综合确定了由于历史和当代因素在许多情况下物种丰富度、种群丰富度和遗传多样性之间的脱钩。范围大小和分类差异似乎在调节种内多样性梯度方面发挥着重要作用。我们鼓励进一步分析，在物种、种群和遗传水平上共同评估多样性梯度理论，以更好地了解地球的生物多样性分布并完善生物多样性保护。