Dissertation Research: Seed Dispersal and Population GeneticStructure

与花粉传播相比，种子传播对遗传结构的影响研究较少。广泛的分类比较未能最终证明扩散方式与种群遗传结构之间的关系。本研究将比较伞形科的三种同域植物，它们主要在通过依附动物进行种子传播的形态适应方面存在差异，以分离种子传播性状对遗传结构的影响。将根据同工酶数据评估15-18个种群内部和种群之间的遗传多样性，种群之间的距离为0.5至100公里。将对两个种群进行更深入的研究，对数百个个体进行图谱和基因分型，并收集种子进行异交分析。这些空间和遗传数据，结合对人口统计学、开花和结果的观察，将用于研究微地理遗传分化和交配系统的模式。田间和实验室的研究将用于估计种子的清除率和果实在分散器上附着和脱离的可能性。生殖植物与种子作物或幼苗之间的遗传和空间距离的相关性将用于评估花粉和种子传播对两个定位群体内基因流动的相对重要性。本研究将有助于了解种子传播机制对种群遗传结构的影响、不同空间尺度上遗传变异分配的数量和质量差异，以及种子和花粉传播对植物种群分化模式影响的相对重要性。由于这些物种发生在自然保护区内相对未受干扰的森林的“栖息地岛”，本研究将为研究栖息地大小和隔离对基因流动和遗传多样性维持的影响提供信息。

The effects of seed dispersal on genetic structure are much less well studied than those of pollen dispersal. Broad taxonomic comparisons have failed to demonstrate conclusively the relationship between mode of dispersal and population genetic structure. The proposed research will compare three sympatric species in the family Umbelliferae, which differ mainly in morphological adaptations for seed dispersal by attachment to animals, to isolate the effects of seed dispersal traits on genetic structure. Genetic diversity within and among 15-18 populations, ranging from 0.5 to 100 km apart, will be evaluated from isozyme data. Two populations will be more intensively studied by mapping and genotyping several hundred individuals, as well as collecting seeds for outcrossing analyses. These spatial and genetic data, combined with observations on demography, flowering and fruiting will be used to investigate patterns of microgeographic genetic differentiation and mating systems. Field and laboratory studies will be used to estimate seed removal rates and attachment and detachment probabilities of fruits on dispersers. Correlations of genetic and spatial distances between reproductive plants and seed crops or seedlings will be used to evaluate the relative importance of pollen and seed dispersal on gene flow within the two mapped populations. This study will contribute to understanding how seed dispersal mechanisms affect population genetic structure, quantitative and qualitative difference in the apportionment of genetic variation at different spatial scales, and the relative importance of the effects of seed versus pollen dispersal on patterns of plant population differentiation. Because these species occur in "habitat islands" of relatively undisturbed forest in nature preserves, this study will provide information with which to examine the effects of habitat size and isolation on gene flow and the maintenance of genetic diversity.