Data from: The relevance of gene flow in metapopulation dynamics of an oceanic island endemic, Olea europaea subsp guanchica

Theoretical and empirical studies suggest that geographical isolation and extinction-recolonization dynamics are two factors causing strong genetic structure in metapopulations. Here, we investigated the effect of population age structure and isolation by distance in the patterns of genetic diversity in a tree species (Olea europaea subsp. guanchica) sporadically affected by volcanic events across the Canarian archipelago. Genetic variation was assessed at six nuclear microsatellites (nDNA) and six chloroplast fragments (cpDNA) in nine subpopulations sampled on four oceanic islands. Subpopulations occurring on more recent substrates were more differentiated than those on older substrates, but within-subpopulation genetic diversity was not significantly different between age groups for any type of marker. Contrary to the general trend for island systems, between-island differentiation was extremely low, and lower than differentiation between subpopulations on the same island. The pollen-to-seed ratio was close to one, two orders of magnitude lower than the average estimated for other wind-pollinated, animal-dispersed plants. Our results showed that population turnover and geographical isolation increased genetic differentiation relative to an island model at equilibrium, but overall genetic structure was unexpectedly weak for a species distributed among islands. This empirical study shows that extensive gene flow, particularly mediated by seeds, can ameliorate population subdivision resulting from extinction-recolonization dynamics and isolation by distance

理论与实证研究均表明，地理隔离与灭绝-拓殖动态是导致集合种群（metapopulations）形成强烈遗传结构的两大核心因素。本研究以加那利群岛（Canarian archipelago）上受火山事件间歇性影响的木本物种——油橄榄加那利群岛亚种（Olea europaea subsp. guanchica）为研究对象，探究了种群年龄结构与距离隔离（isolation by distance）对其遗传多样性格局的影响。研究人员在4个大洋岛屿上采集了9个亚种群样本，通过6个核微卫星（nuclear microsatellites, nDNA）位点与6个叶绿体片段（chloroplast fragments, cpDNA）对遗传变异进行了评估。生长于较新基质的亚种群，其遗传分化程度显著高于生长于较老基质的亚种群；但无论采用哪种标记类型，亚种群内的遗传多样性在不同年龄组间均无显著差异。与岛屿生态系统的普遍规律相悖，岛屿间的遗传分化程度极低，甚至低于同一岛屿内不同亚种群间的分化水平。花粉与种子的传播比值接近1，较其他风媒传粉、动物传播植物的平均估算值低两个数量级。研究结果显示，相较于平衡态岛屿模型，种群更新（population turnover）与地理隔离加剧了遗传分化，但该物种在群岛间的整体遗传结构却意外地偏弱。本实证研究表明，广泛的基因流——尤其是由种子介导的基因流——可有效缓解由灭绝-拓殖动态与距离隔离所引发的种群遗传分化。