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 inter-fertile 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 (F. excelsior) and mixed plantations of non-native ash (F. angustifolia and F. excelsior), as well as hybrid ash (F. excelsior x 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 reproductive success was found for introduced trees compared to native ones either. A small but significant genetic structure was found (Фft = 0.05) but it 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.

当花粉云（pollen clouds）无空间隔离且物候模式（phenological patterns）完全重叠时，可互育的本地与外来植物种群之间的基因流（gene flow）风险最高。此外，若外来种群能够通过自交（selfing）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地梣树（F. excelsior）、非本地梣树混交林（F. angustifolia与F. excelsior）以及杂交梣树（F. excelsior × F. angustifolia）种群，探究了其交配系统（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（flowering phenology）进行了分析，并利用6个微卫星位点（microsatellite loci）对132棵本地与人工林树木（共1493粒种子）的子代阵列（progeny arrays）以及444个潜在亲本进行了基因分型。父本分析（paternity analyses）结果显示，人工林与本地树木的授粉既来自本地种群，也来自外来种群。未观察到外来树木存在显著自交现象，也未发现外来树木的繁殖成功率显著高于本地树木。研究发现了微弱但显著的遗传结构（genetic structure）（Фft = 0.05），但该结构并不符合距离隔离（isolation by distance）模式。然而，我们观察到与不同物候类群（phenological groups）相关的显著时间遗传结构（temporal genetic structure），尤其是早花与晚花的本地梣树；每个物候类群的授粉花粉来源均具有特异性。本文就上述结果的意义展开讨论，涉及梣树的保护与入侵性，以及针对诸如正在摧毁欧洲普通梣树林的真菌病原体Chalara fraxinea的抗性基因（resistance genes）传播。