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）气候波动如何塑造现存树木物种的分布与遗传结构，可为揭示驱动物种分化、分布格局及存续机制的核心过程提供关键见解。阐明过去气候变化引发的遗传效应，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——在地球步入快速气候变化周期的当下，该项研究兼具重要的科学与现实意义。本研究结合遗传数据与生态位模型（Ecological Niche Model），针对野生果树欧洲野苹果（Malus sylvestris，栽培苹果的野生近缘亲本之一）的生物地理分布范围扩张历史格局展开探究。针对末次盛冰期（Last Glacial Maximum）的气候预测结果与微卫星变异分析均显示，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格局：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局限于东欧地区——其一分布于喀尔巴阡山脉周边，另一仅见于巴尔干半岛。近似贝叶斯计算（Approximate Bayesian Computation）被证实是推断这些聚类群演化历史的有力工具，其结果支持三个独立冰期避难所同步分化的演化场景。在这三个种群的分布缝合带中，均检测到了种群间的遗传混合现象。各群体内部均呈现微弱的距离隔离（Isolation by Distance）格局，表明欧洲野苹果在历史上曾发生过较高程度的基因交流。