Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Morelia, Michoacán, México.
Laboratorio Nacional de Análisis y Síntesis Ecológica, Escuela Nacional de Estudios Superiores Unidad Morelia, Universidad Nacional Autónoma de México, Morelia, Michoacán, México.
Sci Rep. 2020 Mar 12;10(1):4584. doi: 10.1038/s41598-020-61394-4.
Pollination and seed dispersal patterns determine gene flow within plant populations. In tropical forests, a high proportion of trees are dioecious, insect pollinated and dispersed by vertebrates. Dispersal vectors and density dependent factors may modulate realized gene flow and influence the magnitude of Fine Scale Genetic Structure (FSGS), affecting individual fitness. Spondias purpurea is a vertebrate-dispersed, insect-pollinated dioecious tropical tree. We assessed the influence of sex ratio, effective and realized gene flow on genetic diversity, FSGS and individual fitness within a 30 ha plot in the tropical dry forest reserve of Chamela-Cuixmala, Mexico. All individuals within the plot were tagged, geo-referenced and sampled for genetic analysis. We measured dbh and monitored sex expression during two reproductive seasons for all individuals. We collected seeds directly from maternal trees for effective pollen dispersal analysis, and analyzed established seedlings to assess realized pollen and seed dispersal. Nine microsatellite loci were used to describe genetic diversity parameters, FSGS and gene flow patterns among different size classes. A total of 354 individuals were located and classified into three size classes based on their dbh (<10, 10-20, and >20 cm). Population sex ratios were male biased and diametric size distributions differed among sexes, these differences may be the result of precocious male reproduction at early stages. Autocorrelation analyses indicate low FSGS (Fj <0.07) across all size classes. Long realized pollen and seed dispersal and differences among effective and realized gene flow were detected. In our study site low FSGS is associated with high gene flow levels. Effective and realized gene flow indicate a population recruitment curve indicating Janzen-Connell effects and suggesting fitness advantages for long-distance pollen and seed dispersal events.
传粉和种子散布模式决定了植物种群内的基因流动。在热带森林中，相当高比例的树种为雌雄异株，由昆虫传粉，并由脊椎动物散布。散布载体和密度依赖因素可能会调节实现的基因流动，并影响细微遗传结构（FSGS）的幅度，从而影响个体适应性。Spondias purpurea 是一种由脊椎动物散布、昆虫传粉的雌雄异株热带树种。我们评估了性别比例、有效和实现的基因流动对遗传多样性、FSGS 和个体适应性的影响，研究地点在墨西哥 Chamela-Cuixmala 的热带干旱森林保护区内，面积为 30 公顷。在该样地内，所有个体都被标记、地理定位并取样进行遗传分析。我们在两个繁殖季节测量了所有个体的胸径和监测了性别表达。我们直接从母树收集种子，以进行有效花粉散布分析，并分析建立的幼苗，以评估实现的花粉和种子散布。使用 9 个微卫星标记来描述遗传多样性参数、FSGS 和不同大小类群之间的基因流动模式。总共定位了 354 个个体，并根据胸径（<10、10-20 和>20 cm）将它们分为三个大小类群。种群的性别比例偏向雄性，而且直径大小分布在两性之间存在差异，这些差异可能是由于早期雄性早熟繁殖所致。自相关分析表明，所有大小类群的 FSGS 都较低（Fj <0.07）。检测到长距离的实现花粉和种子散布以及有效和实现基因流动之间的差异。在我们的研究地点，低 FSGS 与高水平的基因流动有关。有效和实现的基因流动表明，种群招募曲线表明 Janzen-Connell 效应，并暗示长距离花粉和种子散布事件具有适应性优势。
