Data from: Demographic history and the low genetic diversity in Dipteryx alata (Fabaceae) from Brazilian Neotropical savannas

Genetic effects of habitat fragmentation may be undetectable because they are generally a recent event in evolutionary time or because of confounding effects such as historical bottlenecks and historical changes in species' distribution. To assess the effects of demographic history on the genetic diversity and population structure in the Neotropical tree Dipteryx alata (Fabaceae) we used coalescence analyses coupled with species distribution modeling to hindcast its distribution over the last 21,000 yr. Twenty five populations (644 individuals) were sampled and all individuals were genotyped using eight microsatellite loci. All populations presented low allelic richness and genetic diversity. The estimated effective population size was small in all populations and gene flow was negligible among most. We also found a significant signal of demographic reduction in most cases. Genetic differentiation among populations was significantly correlated with geographical distance. Allelic richness showed a spatial cline pattern in relation to the species' paleodistribution 21kyr BP, as expected under a range expansion model. Our results show strong evidences that genetic diversity in D. alata is the outcome of the historical changes in species distribution during the late Pleistocene. Because of this historically low effective population size and the low genetic diversity, recent fragmentation of the Cerrado biome may increase population differentiation, causing population decline and compromising long-term persistence.

生境破碎化（habitat fragmentation）的遗传效应往往难以被检测到，这可能是因为从进化时间尺度而言，该事件通常发生较晚，或是受到历史瓶颈、物种分布历史变化等混杂效应的干扰。为评估种群历史对新热带树种香脂木豆（Dipteryx alata，豆科）的遗传多样性与种群结构的影响，本研究结合溯祖分析（coalescence analyses）与物种分布模型，对其过去21000年的分布进行了回溯预测。本次研究共采样25个种群，合计644个个体，并利用8个微卫星位点（microsatellite loci）对所有个体进行基因分型。所有种群均表现出较低的等位基因丰富度与遗传多样性；所有种群的有效种群大小（effective population size）均偏小，且多数种群间的基因流（gene flow）可忽略不计。我们还发现，多数种群存在显著的种群数量缩减（demographic reduction）信号。种群间的遗传分化（genetic differentiation）与地理距离呈显著正相关。等位基因丰富度呈现出与该物种21000年前古分布相关的空间梯度（spatial cline）模式，符合范围扩张（range expansion）模型的预期。研究结果有力表明，香脂木豆的遗传多样性是晚更新世（late Pleistocene）物种分布历史变化的产物。鉴于该物种历来有效种群规模偏小且遗传多样性较低，塞拉多生物群系（Cerrado biome）近期的生境破碎化可能会加剧种群分化，引发种群衰退并威胁其长期存续。