DISSERTATION RESEARCH: Systematics, Colony Form Evolution and Phenotypic Plasticity within the Family Hydrodictyaceae (Sphaeropleales, Chlorophyta)

绿色藻类（绿藻门）包括五个主要类群，它们存在于海洋和淡水沃茨以及陆地上的土壤和雪中。 它们在形态上多样且无处不在，但只有17，000个物种被定义为这个群体。 绿藻门的分类一直是基于形态学，很少有研究纳入额外的数据来定义物种和评估多样性。具有相似外观的藻类传统上被归类在一起，但随着DNA（分子序列数据）的可用性和使用来重建进化关系（物种起源），人们发现形态学在定义物种边界时可能会产生误导，导致对关系的错误解释和不同的物种名称。 这反过来又导致对生物多样性、水质和古指标值的评估不准确，因此，非常需要使用多种形式的数据来测试形态物种及其关系。 本研究将联合收割机的分子和形态学数据，以解决淡水绿色藻类家庭Hydrodictyaceae（绿藻门），其中包括四个属，Hydrodictyon，盘星藻，Sorastrum和Euastropsis的进化关系和测试种边界。 将从澳大利亚收集水网藻科的多个物种，以更好地评估该组内的多样性，并测试北方和南半球物种之间是否存在地理变异。 将分析从澳大利亚收集的物种的DNA序列，并与从北方获得的物种进行比较。 基于计算机的方法将被用来分析序列，并确定这些物种之间的进化关系，其结果将形成有关扩散和形态进化趋势的假设的基础。 因为已经发现，一些淡水绿色藻类可以改变它们的外观，由于环境线索（表型可塑性），如营养物质，光照水平和温度，因此导致不正确的物种定义，本项目包括一个生长实验，改变这些参数，以检查用于定义盘星藻物种的形态特征的稳定性。由于盘星藻是发现在化石记录和特定的物种被用来重建过去的湖泊水生境，增加地理采样的组合，和可塑性的知识，将有助于解释形态物种，也可能是使用的孢粉学家依靠这一套生物解释过去的湖泊条件。测试的形态种和解决Hydrodictyaceae类群的进化关系将有助于更好地了解形态进化和整体多样性的绿色藻类（绿藻门），和新的分离物的集合将大大扩大公开提供给其他研究人员的类群的数量。研究结果还将有助于更好地评估古生态重建的指标价值，并提高淡水生态系统生物多样性估计的准确性。拟议中的研究提供了与澳大利亚科学家合作的机会，其中一位是绿色藻类超微结构和显微镜方面的专家。此外，这项研究涉及在生物体生物学的几个领域，包括显微镜、分子和培养技术，对一名女研究生进行培训。 这方面的知识将通过指导参与生理学研究的学生传播。

The green algae (Chlorophyta) comprise five major groups that occur in marine and fresh waters, as well as terrestrially in soil and snow. They are morphologically diverse and ubiquitous, yet only 17,000 species have been defined for this group. The classifications within Chlorophyta have been based on morphology, and few studies incorporate additional data to define species and assess diversity. Algae of similar appearance have traditionally been grouped together, but with the availability and use of DNA (molecular sequence data) to reconstruct evolutionary relationships (phylogenies), it has been found that morphology can be misleading when defining species boundaries, resulting in incorrect interpretations of relationships and disparate species designations. This in turn leads to inaccurate assessments of biodiversity, water quality and paleo-indicator value, therefore the need is great to test morphological species and their relationships using multiple forms of data. This study will combine molecular and morphological data to resolve evolutionary relationships and test species boundaries within the freshwater green algal family Hydrodictyaceae (Chlorophyta), which consists of four genera, Hydrodictyon, Pediastrum, Sorastrum and Euastropsis. Multiple species within the Hydrodictyaceae will be collected from Australia to better assess the diversity within this group, and to test whether there is geographic variation between species of the Northern and Southern Hemispheres. DNA sequences will be analyzed from species collected in Australia and compared to those that were obtained from the Northern Hemisphere. Computer-based methods will be used to analyze the sequences and determine the evolutionary relationships between these species and the results will form the basis for hypotheses regarding trends of dispersal and morphological evolution. Because it has been found that some freshwater green algae can change their appearance due to environmental cues (phenotypic plasticity) such as nutrients, light levels, and temperature, and therefore leading to incorrect species definitions, this project includes a growth experiment varying these parameters to examine the stability of the morphological characters used to define species of Pediastrum. Because Pediastrum is found in the fossil record and particular species are used to reconstruct past lake water biotopes, the combination of an increased geographic sampling, and knowledge of plasticity, will assist in the interpretation of morphological species and may also be of use to palynologists who rely on this set of organisms for interpretation of past lake conditions. Testing the morphospecies and resolving the evolutionary relationships of the Hydrodictyaceae taxa will contribute a better understanding of morphological evolution and overall diversity of the green algae (Chlorophyta), and collections of new isolates will greatly expand the number of taxa publicly available to other researchers. Results will also lead to better assessments of indicator value for paleoecological reconstructions and increased accuracy of biodiversity estimates in freshwater ecosystems. The proposed research provides opportunities to collaborate with scientists in Australia, one of which is a specialist in green algal ultrastructure and microscopy. Furthermore, this study involves training of a female graduate student in several fields of organismal biology, including microscopy, molecular and culturing techniques. This knowledge will be disseminated through instruction to students involved in phycological studies.