Dissertation Research: Evolutionary Diversification of Encelia Based on Multiple DNA Sequences

这项博士论文研究项目考察了一组索诺兰和莫哈韦沙漠植物遗传变异的地理模式，以解决两个目标。第一个目标是评估向日葵家族三个属之间的遗传关系，以辨别物种形成是否与加利福尼亚州海湾形成所导致的地理隔离有关。第二个目标是评估脆性灌木种群之间的遗传关系，以了解这些沙漠中的植物种群在上一次冰川时期是如何受到气候变化的影响的。将使用利用DNA序列的系统地理学方法。这种方法首先评估物种内部和物种之间的关系，然后在物种的地质和地理历史的背景下检查这些关系。这项研究具有重要意义，原因有两个。首先，这些数据对于理解冰川、地理隔离、殖民、范围扩大、种群大小波动和基因流动如何影响植物种群的遗传结构将是重要的。其次，很少有研究考察索诺兰和莫哈韦沙漠植物物种的遗传结构和系统地理。此外，本文提出的方法对于这一领域的物种来说是全新的，是发展和推进植物进化遗传学领域的重要途径。该项目还将为一名女研究生提供重要培训，从而有助于提高妇女在科学领域的地位。

This doctoral dissertation research project examines geographic patterns of genetic variation in a group of Sonoran and Mojave Desert plants in order to address two objectives. The first objective is to assess genetic relationships among three genera of the sunflower family in order to discern if speciation is correlated with geographic isolation, resulting from the formation of the Gulf of California. The second objective is to assess genetic relationships among populations of brittlebush, one widespread member of the genus Encelia, in order to understand how plant populations in these deserts were affected by climate change during the last glacial period. A phylogeographic approach, which makes use of DNA sequences, will be used. This approach first estimates relationships within and among species, and then examines these relationships in the context of the geologic and geographic history of the species.This research is significant for two reasons. First, these data will be important for understanding how glaciation, geographical isolation, colonization, range expansion, fluctuations in population size, and gene flow influence genetic structure in plant populations. Second, very few studies have examined genetic structure and phylogeography in plant species of the Sonoran and Mojave Deserts. Furthermore, the approach proposed here is entirely novel for species in this area and is an important approach to develop and advance in the field of plant evolutionary genetics. This project will also provide important training to a female graduate student and, thus, will contribute to the advancement of women in science.