Data from: Temporal change and determinants of maternal reproductive success in an expanding oak forest stand

Global change is generating widespread local-scale expansions of tree populations. During demographic expansions, even small differences in individual reproductive success can generate large differences in the genetic composition of the resulting population. Colonizing tree populations almost invariably show highly skewed distributions of seed production, but the evolution of this reproductive skew during plant recruitment remains understudied. We examine how recruit mortality modifies initial patterns of acorn dispersal and maternal reproductive success in a recently established, expanding Pedunculate oak (Quercus robur) forest stand and test different predictors of successful recruit establishment. We mapped and genotyped a cohort of seedlings (n = 809) emerging within and around the stand (n = 254 adult trees), identified their habitats and monitored their fate until an age of 3 years. Their mother trees were inferred by Bayesian parentage analysis, and the number of assigned descendants was used as a proxy for tree maternal fertility. We examined temporal trends in tree fertility and patterns of dispersal, and tested effects of seed number-quality trade-offs, dispersal failure, dispersal distance and habitat of propagule arrival on the probability of seedling establishment. We observed marked inequality in maternal reproductive success at the time of seedling emergence. A positive relationship between tree fertility and the proportion of non-dispersed seedlings pointed to disperser satiation. An overall seedling mortality of 69% generated considerable reshuffling in the fertility ranking of individual trees. Non-dispersal more than doubled seedling mortality. The establishment success of actually dispersed seedlings was independent of mother fertility and dispersal distance but strongly related to the habitat of arrival. Recruit survival was markedly higher in pine plantations or non-forested areas than in broadleaved forest. Synthesis. A few highly fertile trees dominated reproduction in the stand. Differential recruitment success tended to reduce their initial advantage, however, suggesting that reproductive inequality might rapidly decline as more trees start to reproduce along the expansion process. Our results also suggest that field estimates of size or seed production are unlikely to provide reliable estimates of lifetime reproductive success in trees.全球变化正促使树木种群在局域尺度上发生广泛扩张。在种群拓殖扩张过程中，即便个体繁殖成功率存在细微差异，也会使最终种群的遗传组成产生显著分化。处于拓殖阶段的树木种群几乎普遍呈现出种子产量高度偏斜的分布特征，但植物定植进程中这类繁殖偏斜的演化机制仍未得到充分研究。 本研究以新近建立且正在扩张的夏栎（Pedunculate oak, *Quercus robur*）林分为研究对象，探究定植死亡率如何改变初始的橡子扩散（acorn dispersal）模式与母本繁殖成功率，并检验影响幼苗成功定植的各类预测因子。 我们对林分内及周边萌发的809株实生苗，以及林内的254株成年树木开展了定位与基因分型工作，记录了实生苗的生境类型，并对其直至3龄的存活状态进行了持续监测。通过贝叶斯亲权分析（Bayesian parentage analysis）推断实生苗的母本个体，并以被分配的子代数量作为母本繁殖力的替代指标。我们分析了树木繁殖力的时间动态与扩散模式，检验了种子数量-质量权衡（seed number-quality trade-offs）、扩散失败（dispersal failure）、扩散距离以及繁殖体到达生境对幼苗定植概率的影响。 研究结果显示，在幼苗萌发阶段，母本的繁殖成功存在显著不均等性。树木繁殖力与非扩散幼苗的比例呈正相关关系，这指向扩散者饱和效应（disperser satiation）。总体69%的幼苗死亡率导致了个体树木繁殖力排名发生大幅变动。无法完成扩散的实生苗死亡率较扩散个体高出一倍以上。实际完成扩散的实生苗定植成功率与母本繁殖力及扩散距离均无关联，但与繁殖体到达的生境类型密切相关。人工松林（pine plantations）或非林地（non-forested areas）中的幼苗存活率显著高于阔叶森林（broadleaved forest）中的个体。 综合分析表明，林分内少数繁殖力极强的树木主导了种群繁殖。然而，定植成功率的差异会削弱这些个体的初始繁殖优势，这意味着随着种群扩张进程中更多树木开始参与繁殖，繁殖不均等性可能会快速降低。本研究结果还提示，基于树木体型或种子产量的野外估算，难以可靠反映树木的终身繁殖成功率。