Data from: Investigating the spatial, demographic, and genetic structures of Cylicodiscus gabunensis Harms, a light-demanding African timber species

Most Central African rainforest canopies consist of light-demanding tree species that hold high commercial value but also suffer locally from regeneration deficits, raising concerns about the sustainability of logging. Regeneration is influenced by factors such as past perturbations (including human activity), mating systems, and seed/pollen dispersal processes that impact demographic, spatial, and genetic structures within populations. To gain a better understanding of these interactions, we studied the spatial distribution and trunk diameter structure of Cylicodiscus gabunensis (Fabaceae) - a wind-dispersed, insect-pollinated, timber species - in three plots ranging from 400 to 839 ha situated in various environmental contexts (e.g. forest types and elephant densities) across Central Africa. We also genotyped adults and juveniles using microsatellite markers to analyze the spatial genetic structure of each population and infer the selfing rate, seed and pollen dispersal capacities and selection gradients using the 'neighborhood model'. The selfing rate was low (3 – 4 %), and seed dispersal distances (ds = 184 m) were much shorter than pollen dispersal distances (dp > 2 km). The three populations displayed contrasted spatial, demographic and genetic structures. One population showed no spatial aggregation or genetic structure, and a multimodal diameter structure indicating pulses of regeneration events. Two populations showed strong spatial aggregation and genetic structures. One exhibited a unimodal diameter structure indicating one ancient pulse of regeneration, while the other displayed a 'reverse J-shaped' diameter structure, typical of ongoing regeneration. In the latter, reproductive success appeared leptokurtic, three mother trees accounting for over 90 % of the regeneration and no tree below the minimum cutting diameter implemented by logging companies had offspring. The idiosyncratic nature of population characteristics observed in C. gabunensis suggests that, for sustainable management, a nuanced approach is needed. This involves protecting productive seed trees in areas where natural regeneration is occurring and actively supporting regeneration in areas exhibiting deficits, especially in contexts with low elephant densities.

中非多数雨林冠层由喜光乔木树种构成，这类树种商业价值颇高，但局部区域存在更新不足的问题，由此引发了采伐可持续性的担忧。林木更新受诸多因素影响，包括过往干扰（含人类活动）、交配系统，以及影响种群内人口统计学、空间分布与遗传结构的种子/花粉传播过程。为深入解析这些交互作用，我们针对加蓬盘翼豆（Cylicodiscus gabunensis，豆科Fabaceae）——一种种子风传播、虫媒授粉的用材树种——开展研究，在中非不同环境背景（如森林类型、大象密度）下的3块面积介于400至839公顷的样地中，分析其空间分布与树干直径结构。我们还利用微卫星标记（microsatellite markers）对成年与幼龄个体进行基因分型，以分析各群体的空间遗传结构，并借助邻域模型（neighborhood model）推断自交率、种子与花粉传播能力以及选择梯度。研究结果显示，自交率较低（3%~4%），种子传播距离（ds=184米）远短于花粉传播距离（dp>2千米）；三个种群的空间、人口统计与遗传结构存在显著差异：其中一个种群无空间聚集或遗传结构，且呈现多峰直径结构，表明存在多次更新脉冲事件；另外两个种群则表现出强烈的空间聚集与遗传结构，一个呈现单峰直径结构，指示曾有一次古老的更新脉冲，另一个则呈现反J型（reverse J-shaped）直径结构，这是持续更新的典型特征。在后一类种群中，繁殖成功率呈现尖峰分布（leptokurtic），仅3株母树贡献了超过90%的更新个体，且未达到采伐公司规定的最小采伐直径的个体均未产生后代。本次研究在加蓬盘翼豆种群中观察到的独特特征表明，要实现可持续经营，需采取精细化的管理策略：在自然更新良好的区域保护高产母树，在更新不足的区域主动促进更新，尤其在大象密度较低的环境中更应如此。