Data from: Postglacial recolonization history of the European crabapple (Malus sylvestris Mill.), a wild contributor to the domesticated apple

Understanding the way in which the climatic oscillations of the Quaternary Period have shaped the distribution and genetic structure of extant tree species provides insight into the processes driving species diversification, distribution and survival. Deciphering the genetic consequences of past climatic change is also critical for the conservation and sustainable management of forest and tree genetic resources, a timely endeavour as the Earth heads into a period of fast climate change. We used a combination of genetic data and ecological niche models to investigate the historical patterns of biogeographic range expansion of a wild fruit tree, the European crabapple (Malus sylvestris), a wild contributor to the domesticated apple. Both climatic predictions for the last glacial maximum and analyses of microsatellite variation indicated that M. sylvestris experienced range contraction and fragmentation. Bayesian clustering analyses revealed a clear pattern of genetic structure, with one genetic cluster spanning a large area in Western Europe and two other genetic clusters with a more limited distribution range in Eastern Europe, one around the Carpathian Mountains and the other restricted to the Balkan Peninsula. Approximate Bayesian computation appeared to be a powerful technique for inferring the history of these clusters, supporting a scenario of simultaneous differentiation of three separate glacial refugia. Admixture between these three populations was found in their suture zones. A weak isolation by distance pattern was detected within each population, indicating a high extent of historical gene flow for the European crabapple.

解析第四纪（Quaternary Period）气候振荡如何塑造现存树木物种的分布格局与遗传结构，有助于深入理解驱动物种分化、分布及存续的核心过程。阐明过往气候变化带来的遗传效应，对于森林与树木遗传资源的保护及可持续管理亦至关重要——在全球正步入快速气候变化阶段的当下，这一研究极具现实紧迫性。本研究结合遗传数据与生态位模型，探究一种野生果树——欧洲野苹果（Malus sylvestris）——的生物地理分布扩张历史模式；该物种是栽培苹果的野生亲本之一。末次冰盛期（Last Glacial Maximum）的气候预测结果与微卫星（microsatellite）变异分析均表明，欧洲野苹果曾经历分布范围收缩与片段化过程。贝叶斯聚类分析揭示了清晰的遗传结构模式：一个遗传聚类群广泛分布于西欧大范围区域，另外两个遗传聚类群的分布范围则更为局限于东欧地区——其一分布于喀尔巴阡山脉周边，另一仅局限于巴尔干半岛。近似贝叶斯计算（Approximate Bayesian Computation）被证实为推断这些聚类群演化历史的有效工具，其结果支持三个独立冰期避难所同步分化的演化场景。在三个种群的杂交接触带中，均检测到了种群间的基因混合现象。每个种群内部均检测到微弱的距离隔离模式，表明欧洲野苹果历史上曾存在较高水平的基因交流。