Dissertation Research: Gene Flow and the Scale of Fragmentation in Tropical Tree Populations

DEB 95-20702 哈姆里克 在世界许多地区，特别是在热带地区，砍伐森林的速度令人震惊。 许多注意力都集中在物种多样性，特别是动物多样性的丧失上。 相对较少的努力已经进入研究的影响，破碎化的热带树木种群的动态。 与温带相反，大多数热带树种通过动物媒介传播花粉和种子。 因此，如果传粉者和种子传播者协会被破坏，栖息地破碎化可能会严重影响热带树木种群的完整性。 残留的森林片断之间缺乏分散将导致片断之间几代的遗传分化，并由于与小种群规模相关的人口因素而增加灭绝的可能性。 这些因素的结合会导致物种的遗传多样性随着时间的推移而丧失，这可能会损害其应对未来进化压力的能力。 本研究探讨了栖息地破碎化对基因运动的影响，通过花粉和种子内和之间残留的森林斑块在南部哥斯达黎加的热带雨林。 研究地点包括一个20公顷的碎片化区域，包括三个一公顷的残留斑块和两个一公顷的连续森林控制地块。 将利用分子遗传标记识别研究中心内研究物种的成年和幼苗。 遗传指纹将被用来建立模式的幼苗和父母对发生在研究区域内的父母关系。 不能由居住在地块上的亲本产生的幼苗代表了远距离基因流动的实例。 详细检查研究区域内的父母，幼苗协会将提供重要的证据：补丁之间的遗传连接的数量;在牧场上的自由站立的个人的重要性补丁人口的本地动态;和走廊的花粉和种子的运动的重要性。 这些数据将为异质环境中基因流动模式提供经验视角，并为热带地区的保护和热带保护区的设计提供必要的信息。

DEB 95-20702 Hamrick Deforestation is occurring at an alarming rate in many parts of the world, especially in tropical regions. Much attention has been focused on the resultant loss of species diversity, particularly of animals. Relatively little effort has gone into examining the effects of fragmentation on the dynamics of tropical tree populations. In contrast to the temperate zone, most tropical tree species disperse pollen and seeds by means of animal vectors. Thus, it is likely that habitat fragmentation could seriously impact the integrity of tropical tree populations if pollinator and seed disperser associations are disrupted. A lack of dispersal among remnant forest fragments would lead to genetic differentiation among fragments over several generations and an increased probability of extinction due to demographic factors associated with small population size. This combination of factors should lead to a loss of genetic diversity in the species over time which could compromise its ability to respond to future evolutionary pressures. This study examines the effects of habitat fragmentation on gene movement via pollen and seed within and among remnant forest patches in premontane tropical rain forest in southern Costa Rica. The study site consists of a 20 hectare fragmented area including three one-hectare remnant patches plus two one-hectare plots in continuous forest for control. Molecular genetic markers will be utilized to identify adults and young seedlings of the study species occurring within the study sites. Genetic fingerprints will be used to establish patterns of parental relationship between seedlings and parent-pairs occurring within the study region. Seedlings that cannot be produced by parents resident on the plot represent instances of long-distance gene flow. The detailed examination of parent-seedling associations within the study regions will provide important evidence regarding: the amount of genetic connectedness among patches; the importance of f ree-standing individuals in pastures to the local dynamics of patch populations; and the importance of corridors to the movement of pollen and seeds. These data will provide an empirical perspective on patterns of gene flow in a heterogeneous environment and will prmvide necessary information for the conservation of tropical areas and the design of tropical reserves.