Dissertation Research: Population Structure in Ponderosa Pine

9520381米顿对植物种群的有效管理（无论是出于经济目的还是出于保护目的）需要了解种群之间的遗传差异，因为这些差异可能反映了每个种群对当地环境的适应。我们对种群分化的理解大部分来自于对蛋白质基因的研究。本研究将利用最新的DNA技术来比较黄松自然种群中蛋白质基因与其他类型基因的发现。数据收集很简单，包括测量来自西南部黄松分布范围的南北样带种群之间的遗传分化量。基因差异是通过测定被研究人群中DNA类型（“等位基因”）的频率来测量的，这些DNA类型来自带回实验室的针组织样本。这项研究将从两个方面促进我们的认识。首先，通过比较不同类型基因之间的遗传差异模式，可以检验旧的发现。理论预测种群间遗传差异的大小将由种群间迁移和杂交的数量决定。由于所有基因的迁移量是相同的，所以所有的基因座在种群之间应该显示出相同的差异幅度。如果不是，那么“不适合”的基因很可能受到其他因素的影响，比如适应当地条件的选择。其次，该研究将比较从父母双方遗传的基因（大多数基因）和仅从父母一方遗传的基因。松树提供了一个独特的机会来做到这一点，因为叶绿体DNA是父系遗传的（通过花粉），而线粒体DNA是母系遗传的（通过种子）。通过比较具有这些不同遗传模式的基因群体之间的相对差异，研究人员可以测量种子和花粉的相对迁移量。理解这一点很重要，因为只有种子迁移才能找到新的种群，而迁移的花粉仅限于在现有种群之间移动。

9520381 Mitton Effective management of plant populations (either for economic or conservation purposes) requires an understanding of the genetic differences among populations, since these differences may reflect adaptation to the local environments in which each population lives. Much of our understanding of population differentiation has been derived from the study of protein genes. This proposed research will make use of recent DNA technologies to compare the findilgs from protein genes to other types of gene, in natural populations of ponderosa pine. The data collection is straightforward, and consists of measuring the amount of genetic differentiation between populations in a north-south transect through the range of ponderosa pine from the Southwest. Genetic differences are measured by determining the frequency of DNA types ("alleles") in each population under study, from samples of needle tissue brought back to the laboratory. This study will advance our understanding in two ways. First, by comparing patterns of genetic differences between different types of genes, older findings can be tested. Theory predicts that the size of genetic differences among populations will be determined by the amount of migration and interbreeding between them. Since the amount of migration is the same for all genes, all loci should show the same magnitude of difference between populations. If not, then genes which "don't fit" are likely to be affected by some other factor, such as selection to adapt to local conditions. Second, the study will compare those genes inherited from both parents (most genes) with those inherited solely from one parent. Pines provide a unique opportunity to do this in that chloroplast DNA is inherited paternally (through the pollen), while mitochondrial DNA is maternally inherited (through the seed). By comparing the relative differences between populations for genes with these contrasting inheritance patterns, the investigators can measure the relative amount of mig ration by both seeds and pollen. It is important to understand this, because only seed migrants can found new populations, while migrant pollen is restricted to movement between existing populations.