Population Biology of Tropical Rain Forest Trees

砍伐森林对热带雨林植物物种灭绝率的影响是有据可查的。关于森林砍伐对树种内遗传变异丧失的影响，人们知之甚少，因为没有关于自然种群遗传变异的数量和空间分布模式的足够信息。遗传变异被认为是种群长期生存的重要因素。因此，关于种群内和种群间遗传变异的数量和模式的信息对于设计适当的措施以保护热带树木种群至关重要。同样重要的是了解遗传因素，如交配系统和种群之间的基因交流水平，这些因素对遗传变异的分布有很大影响。热带雨林中的许多树种的种群密度都很低。小种群可能会失去遗传变异，还可能受到近亲繁殖抑制(近亲交配对生殖产出的有害影响)。因此，研究调节物种遗传变异的因素尤为重要，这些因素通常发生在低密度环境中。本研究的目的是1.分析遗传变异的数量和模式，2.估计有效种群规模，3.测量异交(或近交)的比率，4.确定种群间的基因交换水平，5.研究密度对热带低地雨林天然种群近交水平和繁殖产量的影响。实地工作将在哥斯达黎加热带研究组织的La Selva生物野外站进行，实验室工作将在波士顿的马萨诸塞大学进行。

The effects of deforestation on the extinction rates of plant species in tropical rain forests are well documented. Less is known about the impact of deforestation on the loss of genetic variation within tree species because there is not enough information about the amount and patterns of spatial distribution of genetic variation in natural populations. Genetic variation is considered to be important in the long term survival of populations. Thus, information about the amount and patterns of genetic variation within and among populations is central to the design of appropriate measures to conserve tropical tree populations. Equally important is to understand the genetic factors, such as mating systems and the level of gene exchange among populations, which greatly influence the distribution of genetic variation. Many tree species in tropical rain forests have low population density. Small populations may lose genetic variation, and may also be subject to inbreeding depression (deleterious effects in reproductive output due to mating among close relatives). Thus, it is paricularly important to study factors regulating genetic variation in species that typically occur in low densities. The objectives of this research are to 1. analyze the amount and patterns of genetic variation, 2. estimate effective population size, 3. measure the rate of outcrossing (or inbreeding), 4. determine the level of gene exchange among populations, and 5. examine the effects of density on the level of inbreeding and reproductive output in natural populations of tropical lowland rain forest trees. The field work will be conducted at the La Selva Biological Field Station of the Organization for Tropical Studies in Costa Rica, and the laboratory work at the University of Massachusetts at Boston.