Data from: Low plant density enhances gene dispersal in the Amazonian understory herb Heliconia acuminata

In theory, conservation genetics predicts that forest fragmentation will reduce gene dispersal, but in practice, genetic and ecological processes are also dependent on other population characteristics. We used Bayesian genetic analyses to characterize parentage and propagule dispersal in Heliconia acuminata L. C. Richard (Heliconiaceae), a common Amazonian understory plant that is pollinated and dispersed by birds. We studied these processes in two continuous forest sites and three 1-ha fragments in Brazil's Biological Dynamics of Forest Fragments Project. These sites showed variation in the density of H. acuminata. Ten microsatellite markers were used to genotype flowering adults and seedling recruits and to quantify realized pollen and seed dispersal distances, immigration of propagules from outside populations, and reproductive dominance among parents. We tested whether gene dispersal is more dependent on fragmentation or density of reproductive plants. Low plant densities were associated with elevated immigration rates and greater propagule dispersal distances. Reproductive dominance among inside-plot parents was higher for low density than for high density populations. Elevated local flower and fruit availability is probably leading to spatially more proximal bird foraging and propagule dispersal in areas with high density of reproductive plants. Nevertheless, genetic diversity, inbreeding coefficients and fine-scale spatial genetic structure were similar across populations, despite differences in gene dispersal. This result may indicate that the opposing processes of longer dispersal events in low-density populations versus higher diversity of contributing parents in high-density populations balance the resulting genetic outcomes and prevent genetic erosion in small populations and fragments.理论上，保护遗传学（conservation genetics）预测森林破碎化会降低基因流（gene dispersal），但实际中遗传与生态过程同时还受其他种群特征的调控。我们采用贝叶斯遗传分析（Bayesian genetic analyses），对亚马逊林下常见、由鸟类传粉并传播繁殖体的锐尖蝎尾蕉（Heliconia acuminata L. C. Richard，蝎尾蕉科Heliconiaceae）的亲本关系与繁殖体传播特征进行了系统表征。我们在巴西森林碎片生物动力学项目（Biological Dynamics of Forest Fragments Project）的2块连续森林样地与3块1公顷的破碎化样地中开展了上述过程的研究，这些样地的锐尖蝎尾蕉种群密度存在显著差异。我们利用10个微卫星（microsatellite）标记对开花成株与幼苗补充个体进行基因分型，并量化了实际花粉与种子传播距离、外来繁殖体的种群迁入率以及亲本间的生殖优势。我们检验了基因流更依赖于森林破碎化程度还是繁殖植株的种群密度。研究结果显示：较低的植株密度与更高的繁殖体迁入率和更远的繁殖体传播距离相关；低密度种群样地内亲本的生殖优势显著高于高密度种群。局部较高的花与果实可获得性，可能会使鸟类在繁殖植株高密度区域的觅食空间范围更局限，进而导致繁殖体传播距离更近。尽管基因流存在显著差异，但所有种群的遗传多样性、近交系数以及精细尺度空间遗传结构均无显著差异。这一结果表明，低密度种群中更远的传播事件与高密度种群中更多样的贡献亲本这两种对立过程，共同平衡了最终的遗传结果，从而避免了小种群与破碎化种群发生遗传侵蚀（genetic erosion）。