Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, United Kingdom ; INRA, UMR 1224, Ecologie Comportementale et Biologie des Populations de Poissons, Saint Pée sur Nivelle, France ; Univ Pau & Pays Adour, UMR 1224, Ecologie Comportementale et Biologie des Populations de Poissons, Anglet, France.
PLoS One. 2013 Sep 30;8(9):e75029. doi: 10.1371/journal.pone.0075029. eCollection 2013.
Populations located at the rear-edge of a species' distribution may have disproportionate ecological and evolutionary importance for biodiversity conservation in a changing global environment. Yet genetic studies of such populations remain rare. This study investigates the evolutionary history of North-African low latitude marginal populations of Alnus glutinosa Gaertn., a European tree species that plays a significant ecological role as a keystone of riparian ecosystems. We genotyped 551 adults from 19 populations located across North Africa at 12 microsatellite loci and applied a coalescent-based simulation approach to reconstruct the demographic and evolutionary history of these populations. Surprisingly, Moroccan trees were tetraploids demonstrating a strong distinctiveness of these populations within a species otherwise known as diploid. Best-fitting models of demographic reconstruction revealed the relict nature of Moroccan populations that were found to have withstood past climate change events and to be much older than Algerian and Tunisian populations. This study highlights the complex demographic history that can be encountered in rear-edge distribution margins that here consist of both old stable climate relict and more recent populations, distinctively diverse genetically both quantitatively and qualitatively. We emphasize the high evolutionary and conservation value of marginal rear-edge populations of a keystone riparian species in the context of on-going climate change in the Mediterranean region.
位于物种分布后缘的种群，对于变化的全球环境中的生物多样性保护可能具有不成比例的生态和进化重要性。然而，对这些种群的遗传研究仍然很少。本研究调查了欧洲树种桤木在北非低纬度边缘种群的进化历史，桤木作为河岸生态系统的关键物种，具有重要的生态作用。我们在 12 个微卫星基因座上对来自北非 19 个种群的 551 个成年人进行了基因分型，并应用基于合并的模拟方法来重建这些种群的人口和进化历史。令人惊讶的是，摩洛哥的树木是四倍体，表明这些种群在其他已知的二倍体物种中具有很强的独特性。人口重建的最佳拟合模型揭示了摩洛哥种群的残余性质，这些种群经受住了过去的气候变化事件，并且比阿尔及利亚和突尼斯的种群要古老得多。本研究强调了在边缘分布后缘可能遇到的复杂人口历史，这里既有古老的稳定气候残余种群，也有最近的种群，在数量和质量上都具有独特的多样性。我们强调了在正在进行的地中海地区气候变化背景下，作为关键河岸物种的边缘后缘种群的高进化和保护价值。
