Data from: Crop-to-wild gene flow and its fitness consequences for a wild fruit tree: towards a comprehensive conservation strategy of the wild apple in Europe

Crop-to-wild gene flow can reduce the fitness and genetic integrity of wild species. Malus sylvestris, the European crabapple fruit tree, in particular is threatened by the disappearance of its habitat and by gene flow from its domesticated relative, Malus domestica. With the aims of evaluating threats for M. sylvestris and of formulating recommendations for its conservation, we studied here, using microsatellite markers and growth experiments: i) hybridization rates in seeds and trees from a French forest and in seeds used for replanting crabapples in agrosystems and in forests, ii) the impact of the level of M. domestica ancestry on individual fitness tree, and iii) pollen dispersal abilities in relationship with crop-to-wild gene flow. We found substantial contemporary crop-to-wild gene flow in crabapple tree populations and superior fitness of hybrids compared to wild seeds and seedlings. Using paternity analyses, we showed that pollen dispersal could occur up to 4 km and decreased with tree density. The seed network furnishing the wild apple reintroduction agroforestry programs was found to suffer from poor genetic diversity, introgressions, and species misidentification. Overall, our findings indicate supported threats for the European wild apple steering us to provide precise recommendations for its conservation.

作物向野生近缘种的基因流会降低野生物种的适合度与遗传完整性。欧洲野苹果（Malus sylvestris），即欧洲海棠果树，其生存尤其受到栖息地丧失以及与其驯化近缘种栽培苹果（Malus domestica）间基因流的威胁。为评估欧洲野苹果面临的生存威胁并制定针对性保护建议，本研究借助微卫星标记（microsatellite markers）与生长实验开展了三项研究：（1）法国森林中的野生种子与植株，以及农林业与森林中用于补植海棠树的种子的杂交率；（2）栽培苹果祖先血统占比对单株果树适合度的影响；（3）与作物-野生基因流相关的花粉扩散能力。本研究发现海棠树种群中存在显著的当代作物-野生基因流现象，且杂交后代的适合度优于野生种子与实生苗。通过父本分析（paternity analyses），我们证实花粉扩散距离可达4公里，并随植株密度升高而降低。用于野苹果再引入农林业项目的种子网络被发现存在遗传多样性低下、基因渐渗以及物种误鉴等问题。综上，本研究结果证实欧洲野苹果面临切实的生存威胁，因此可为其保护制定精准的建议方案。