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.
