CRB: Conservation Genetics of Tropical Forest Trees

9400147 Bawa本提案的总体目标是研究森林砍伐和森林破碎化对哥斯达黎加热带低地雨林遗传多样性、基因扩散和交配模式的影响。具体目标是：（1）在相对较小的空间尺度上测量热带树木种群的遗传分化量，（2）确定分散种群的矩阵是否具有与同等大小的大片森林区域相同的遗传多样性水平，（3）计算大片连续森林中、小片段之间以及片段与大片森林保护区之间的基因流动水平，（4）评估小片段树木的近亲繁殖水平，并将其与大型连续森林中的树木进行比较，（5）确定远系繁殖的下降是否与近亲繁殖衰退有关。遗传变异将使用各种遗传标记和形态特征进行研究。PI为热带树种开发的简单重复序列（SSR）将用于估计基因流动和近亲繁殖的水平。SSR位点具有高度的变异性和巨大的区分力，但尚未用于植物自然群体的研究。 砍伐森林和森林片断化在热带地区普遍存在，据推测会导致生物多样性的丧失，包括物种内的遗传多样性。然而，没有关于热带森林树种内遗传多样性损失的估计。缺乏知识的一个原因是对热带树木的种群遗传学知之甚少。此外，森林片断化的遗传后果取决于片断之间以及片断与大片连续森林之间的基因交换水平。 从这项研究中获得的信息将有助于评估森林砍伐对遗传多样性的影响。本研究还将提供信息的比较效用的各种标记估计群体遗传参数。

9400147 Bawa The overall aim of this proposal is the examine the effect of deforestation and forest fragmentation on genetic diversity, gene dispersal, and mating patterns in tropical lowland rain forests of Costa Rica. The specific goals are to: (1) measure the amount of genetic differentiation in tropical tree populations over relatively small spatial scales, (2) ascertain if a matrix of fragmented populations possesses the same level of genetic diversity as a large forest area of equal size, (3) calculate the levels of gene flow in a large contiguous forest, among small fragments, and between fragments and large forest reserves, (4) assess the level of inbreeding for trees in small fragments and compare this to trees in large contiguous forests, and (5) determine if a decline in outbreeding is associated with inbreeding depression. Genetic variation will be studies using a variety of genetic markers and morphological traits. Simple Sequence Repeats (SSR's) that have been developed by the PI for tropical tree species will be used to estimate levels of gene flow and inbreeding. SSR's loci are highly variable with a tremendous discriminatory power, but have not been used in the study of natural populations of plants. %%% Deforestation and forest fragmentation are ubiquitous in the tropics and are presumed to result in loss of biodiversity, including genetic diversity within species. However, there are no estimates of loss of genetic diversity within species of tropical forest trees. One reason for this lack of knowledge is that the population genetics of tropical trees is poorly understood. Moreover, the genetic consequences of forest fragmentation depend on the levels of gene exchange among fragments and between fragments and large continuous tracts of forest. The information attained from this research will be useful in assessing the impact of deforestation on genetic diversity. This research will also provide information about the comparative utility of various markers for estimating pop ulation genetic parameters.