Dissertation Research: Population Structure in Ponderosa Pine

9520381 Mitton有效管理植物种群(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出对每个种群所生活的当地环境的适应。我们对种群分化的许多理解都源于对蛋白质基因的研究。这项拟议的研究将利用最新的DNA技术来比较黄皮松自然种群中蛋白质基因和其他类型基因的差异。数据收集很简单，包括通过西南地区的黄皮松范围测量南北样带种群之间的遗传分化数量。遗传差异是通过从带回实验室的针组织样本中确定每个被研究群体中DNA类型(“等位基因”)的频率来衡量的。这项研究将从两个方面促进我们的理解。首先，通过比较不同类型基因之间的遗传差异模式，可以检验较早的发现。理论预测，种群间遗传差异的大小将取决于它们之间的迁徙和杂交的数量。由于所有基因的迁移量是相同的，所以所有基因座在不同群体之间应该表现出同样大小的差异。如果不是，那么“不适合”的基因很可能会受到其他因素的影响，比如选择适应当地条件的基因。其次，这项研究将比较那些从父母双方遗传的基因(大多数基因)和那些只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)。通过比较种群间基因的相对差异和这些不同的遗传模式，研究人员可以测量种子和花粉的MiG比率的相对量。理解这一点很重要，因为只有种子迁徙才能发现新的种群，而迁徙的花粉仅限于在现有种群之间流动。

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.