The ‘centre–periphery hypothesis’ (CPH) is a long‐standing postulate in ecology that states that genetic variation and demographic performance of a species decrease from the centre to the edge of its geographic range. This hypothesis is based on an assumed concordance between geographical peripherality and ecological marginality such that environmental conditions become harsher towards the limits of a species range. In this way, the CPH sets the stage for understanding the causes of distribution limits. To date, no study has examined conjointly the consistency of these postulates. In an extensive literature review we discuss the birth and development of the CPH and provide an assessment of the CPH by reviewing 248 empirical studies in the context of three main themes. First, a decrease in species occurrence towards their range limits was observed in 81% of studies, while only 51% demonstrated reduced abundance of individuals. A decline in genetic variation, increased differentiation among populations and higher rates of inbreeding were demonstrated by roughly one in two studies (47, 45 and 48%, respectively). However, demographic rates, size and population performance less often followed CPH expectations (20–30% of studies). We highlight the impact of important methodological, taxonomic, and biogeographical biases on such validation rates. Second, we found that geographic and ecological marginality gradients are not systematically concordant, which casts doubt on the reliability of a main assumption of the CPH. Finally, we attempt to disentangle the relative contribution of geographical, ecological and historical processes on the spatial distribution of genetic and demographic parameters. While ecological marginality gradients explain variation in species' demographic performance better than geographic gradients, contemporary and historical factors may contribute interactively to spatial patterns of genetic variation. We thereby propose a framework that integrates species' ecological niche characteristics together with current and past range structure to investigate spatial patterns of genetic and demographic variation across species ranges.

中文翻译：

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遗传和人口统计表现的地理变异：来自旧生物地理学范式的新见解

“中心-边缘假说” (CPH) 是生态学中一个长期存在的假设，它指出物种的遗传变异和人口统计学性能从其地理范围的中心到边缘递减。该假设基于地理边缘性和生态边缘性之间的假设一致性，因此环境条件在接近物种范围的极限时变得更加恶劣。通过这种方式，CPH 为了解分布限制的原因奠定了基础。迄今为止，还没有研究联合检查这些假设的一致性。在广泛的文献综述中，我们讨论了 CPH 的诞生和发展，并通过在三个主要主题的背景下回顾了 248 项实证研究，对 CPH 进行了评估。第一的，在 81% 的研究中观察到物种出现减少到它们的范围限制，而只有 51% 表明个体数量减少。大约二分之一的研究（分别为 47%、45% 和 48%）证明了遗传变异的减少、种群间分化的增加和近亲繁殖率的提高。然而，人口比率、规模和人口表现较少遵循 CPH 预期（20-30% 的研究）。我们强调了重要的方法学、分类学和生物地理偏差对此类验证率的影响。其次，我们发现地理和生态边缘梯度不是系统一致的，这对 CPH 主要假设的可靠性提出了质疑。最后，我们试图解开地理、遗传和人口参数空间分布的生态和历史过程。虽然生态边缘梯度比地理梯度更好地解释了物种人口表现的变化，但当代和历史因素可能对遗传变异的空间模式有交互作用。因此，我们提出了一个框架，将物种的生态位特征与当前和过去的范围结构相结合，以研究跨物种范围的遗传和人口变异的空间模式。当代和历史因素可能对遗传变异的空间模式产生交互作用。因此，我们提出了一个框架，将物种的生态位特征与当前和过去的范围结构相结合，以研究跨物种范围的遗传和人口变异的空间模式。当代和历史因素可能对遗传变异的空间模式产生交互作用。因此，我们提出了一个框架，将物种的生态位特征与当前和过去的范围结构相结合，以研究跨物种范围的遗传和人口变异的空间模式。