Dissertation Research: Phylogenetics of Neotropical Fern Genus, Jamesonia, and its Closest Relatives

9801245 Mishler Jamesonia是一种主要的安第斯蕨类植物，其营养和生态特性在蕨类植物中是独一无二的。这组高度改良的蕨类植物表现出一系列形态特征，可能与新热带坡地生态系统中普遍存在的极端环境因素有关。坡道一词一般是指海拔3200米到5000米之间的安第斯高地，位于森林上方，永久积雪高度以下。坡道和云雾森林生态系统中存在的令人惊叹的植物多样性是安第斯山脉形成期间地质复杂事件的结果。詹姆松和它的近亲Eriosorus是两个密切相关的类群的一个很好的例子，它们在一个新出现的栖息地进化和多样化。这项研究的最初目标是阐明詹姆松属及其近亲的系统发育关系。为了回答这个问题，我们将研究两个不同的系统发育水平：1)根据叶绿体基因rbcL的形态特征和DNA序列数据，研究带蕨亚科(Pteridaceae)较高水平的系统发育；2)根据18-26S核糖体DNA(NrDNA)内的内部转录间隔区(ITS)的形态特征和序列数据，研究Jamesonia和Eriosorus的较低水平的系统发育。这项研究的第二个目标是调查这一群体进化的生态条件和生物地理背景。将使用生物地理和生态数据的量化比较方法，在上述系统发展的背景下推断多样化进程。在系统发育的框架内，我们将继续对Jamesonia和Eriosorus的异母细胞系进行比较研究，以帮助我们理解个体发育过程与形态多样性之间的关系。

9801245 Mishler Jamesonia is a mainly Andean genus of ferns that is unique among the ferns in its vegetative and ecological characteristics. This highly modified group of ferns exhibits a suite of morphological features perhaps related to the extreme environmental factors prevailing in Neotropical p ramo ecosystems. The term p ramo generally refers to Andean highlands, between 3200 and 5000 m altitude, located above the forest and below the permanent snow levels. The amazing diversity of the flora present in the p ramo and cloud forest ecosystems is the result of geologically complex events during the formation of the Andes. Jamesonia and its closest relative Eriosorus are a good example of two closely related taxa that evolved and diversified in a newly arisen habitat. The initial goal of this study is to clarify the phylogenetic relationships of Jamesonia and its closest relatives. To answer this question two different phylogenetic levels will be studied: 1) a higher-level phylogeny of the subfamily Taenitidoideae (Pteridaceae), based on morphological characters and DNA sequence data from the chloroplast gene rbcL, and 2) a lower-level phylogeny of Jamesonia and Eriosorus, based on morphological characters and sequence data of the internal transcribed spacers (ITS) within the 18-26S nuclear ribosomal DNA (nrDNA). The second goal of this study is to investigate the ecological conditions and biogeographic context of the evolution of this group. A quantitative comparative approach using biogeographic and ecological data will be used to infer processes of diversification in the context of the above phylogenies. Comparative studies on the heteroblastic series of Jamesonia and Eriosorus, within the phylogenetic framework, will be pursued to contribute in our understanding of the relationships between ontogenetic processes and morphological diversification.