Data from: Thank you for not flowering: conservation genetics and gene flow analysis of native and non-native populations of Fraxinus (Oleaceae) in Ireland

The risks of gene flow between interfertile native and introduced plant populations are greatest when there is no spatial isolation of pollen clouds and phenological patterns overlap completely. Moreover, invasion probabilities are further increased if introduced populations are capable of producing seeds by selfing. Here we investigated the mating system and patterns of pollen-mediated gene flow among populations of native ash (Fraxinus excelsior) and mixed plantations of non-native ash (F. angustifolia and F. excelsior) as well as hybrid ash (F. excelsior × F. angustifolia) in Ireland. We analysed the flowering phenology of the mother trees and genotyped with six microsatellite loci in progeny arrays from 132 native and plantation trees (1493 seeds) and 444 potential parents. Paternity analyses suggested that plantation and native trees were pollinated by both native and introduced trees. No signs of significant selfing in the introduced trees were observed and no evidence of higher male reproductive success was found for introduced trees compared with native ones either. A small but significant genetic structure was found (φft=0.05) and did not correspond to an isolation-by-distance pattern. However, we observed a significant temporal genetic structure related to the different phenological groups, especially with early and late flowering native trees; each phenological group was pollinated with distinctive pollen sources. Implications of these results are discussed in relation to the conservation and invasiveness of ash and the spread of resistance genes against pathogens such as the fungus Chalara fraxinea that is destroying common ash forests in Europe.

当可杂交的本土与外来植物种群之间无花粉云空间隔离且物候模式完全重叠时，二者间的基因流动风险最高。此外，若外来种群能够通过自交产生种子，则入侵概率会进一步升高。本研究针对爱尔兰境内的本土白蜡树（Fraxinus excelsior）、非本土白蜡树（F. angustifolia与F. excelsior）混交人工林以及杂交白蜡树（F. excelsior × F. angustifolia）的种群，调查了其交配系统（mating system）与花粉介导的基因流（pollen-mediated gene flow）模式；我们对母树的开花物候进行了分析，并利用6个微卫星位点（microsatellite loci）对132株本土与人工林母树（共1493粒种子）的子代群体以及444份潜在父本材料进行了基因分型。父本分析（paternity analyses）结果显示，人工林与本土母树均接受了本土与外来树木的花粉授粉，未观察到外来树木存在显著自交现象，同时也未发现外来树木的雄性生殖成功率高于本土树木的证据。研究发现了微弱但显著的遗传结构（φft=0.05），且该结构不符合距离隔离模式（isolation-by-distance pattern），但我们观察到与不同物候类群相关的显著时间遗传结构，其中尤以开花早晚不同的本土树木类群最为明显；每个物候类群均接受了特征性的花粉源授粉。本文最后讨论了本研究结果对白蜡树保护与入侵性的启示，以及针对欧洲境内正在摧毁普通白蜡林的真菌病原菌Chalara fraxinea的抗病基因传播的相关影响。