Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references (leaves 172-182). Available also in an electronic version.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

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The genus Iliamna Greene has a taxonomically complex history. Since its desciption in 1906, the genus was not recognized for some time, several species were initially placed into other genera, and the species status of a few was questioned. Today, eight species of Iliamna are recognized. Six species are located in western North America and two are found isolated to the east. Species in Iliamna are very similar morphologically with only a few characters distinguishing several as separate entities. The need for systematic study became apparent since all but one species are considered rare or endangered. Also, the differentiation between two endangered species, I. corei and I. remota, was unclear in a previous study using random amplified polymorphic DNA fragments. Of the western species, four overlap in distribution (I. crandallii, I grandi ora, I. longisepala, and I. rivularis) and their recognition as separate species has been questioned. The focus of this study was to develop a phylogeny for Iliamna using sequences from the internal transcribed spacer region (ITS) of the nuclear ribosomal RNA genes in order to determine its biogeographical and evolutionary history. Cladistic analysis was performed and the resulting phylogeny is presented. The ITS data provide new insights in the origination of the genus and its distribution. In Iliamna, the ITS region is 677 base pairs long with 120 sites providing information in the formation of phylogenetic trees. Iliamna forms a well-supported clade distinct from related genera and is monophyletic. Three well-supported groups are formed. One contains representatives from the Pacific Northwest. Another contains all of the remaining species with the third clade nested therein. This last clade contains the two eastern species, I. corei and I. remota, but there is not enough variability to support the divergence of these taxa as distinct species. There is also not sufficient variability in the ITS region to identify the western species I. crandallii, I. grandi ora, I. longisepala and I. rivularis as distinct entities. / Master of Science

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O gênero Pavonia, provavelmente o maior da família Malvaceae, é representado por 250 espécies, 224 nas Américas (ausente apenas no Chile) e 134 no Brasil. Situa-se na tribo Malvavisceae, por possuir o dobro de estiletes e estigmas na flor em relação ao número de carpelos. Trata-se de um gênero que é representado por ervas prostradas, subarbustos, arbustos e raramente por pequenas árvores. Os objetivos do presente trabalho são: 1) levantamento florístico e produção de uma chave dicotômica para os gêneros nativos da subfamília Malvoideae no Rio Grande do Sul; 2) estudo taxonômico das espécies nativas do gênero Pavonia no Rio Grande do Sul com a) caracterização do gênero Pavonia, b) levantamento das espécies de Pavonia presentes no Rio Grande do Sul, através de revisão de espécimes depositados nos herbários e coletas realizadas em diversas regiões do Estado e c) fornecimento de meios para a identificação das espécies: chave analítica, descrições e ilustrações. Foram percorridas todas as regiões fisiográficas do Rio Grande do Sul (20 expedições, 50 dias em campo) e foi revisado o material de 20 herbários do Sul do Brasil, Uruguai e Argentina, totalizando 1450 exsicatas observadas. Foram catalogadas 34 espécies, 31 delas coletadas e três apenas observadas em exsicatas, totalizando 221 espécimes incluídos no herbário ICN. Estas espécies estão distribuídas em três subgêneros, quatro seções e três subseções. Destaca-se a descrição de três novas espécies, uma nova ocorrência para o Brasil, quatro novas ocorrências para o Rio Grande do Sul e duas sinonimizações. Muitas espécies de Pavonia são raras e apresentam pequena área de ocorrência, fato que, aliado à perda de seu hábitat pela expansão de monoculturas e hidrelétricas, faz necessária a sua inclusão na Lista Oficial da Flora Ameaçada do Rio Grande do Sul. / The genus Pavonia, probably the largest within Malvaceae family, is represented by 250 species, out of which 224 are from America (absent only in Chile) and 134 from Brazil. It is placed in tribe Malvavisceae, because it has twice as many styles and stigmas as it has carpels. Pavonia is a genus represented by prostate herbs, subshrubs, shrubs and rarely small trees. The objectives of the present study were: 1) a floristic survey and the elaboration of a key for the native genera of subfamilyMalvoideae in Rio Grande do Sul and 2) a taxonomic study of the native species of Pavonia in Rio Grande do Sul, encompassing: a) characterization of the genus Pavonia, b) survey of the Pavonia species present in Rio Grande do Sul, through herbaria revision and fresh collected specimens throughout the State and c) provide means for identification of the species: key, descriptions and illustrations. All the physiographical regions of Rio Grande do Sul were surveyed (20 expeditions and 50 days on the field) and material from 20 herbaria of Southern Brazil, Uruguay and Argentina were revised, comprising 1.450 observed specimens. We catalogued 34 species, out of which 31 were collected and three were only observed in herbaria. A total of 221 specimens were included in ICN herbarium. The species are distributed in three subgenera, four sections and three subsections. Emphasis was given for the description of three new species, one new occurrence for Brazil, four new occurrences for Rio Grande do Sul and one synonymizing. Many Pavonia species are rare, and occurred in small geographical areas. In addition, the loss of their habitat, coupled with the expansion of monocultures and construction of dams, emphasizes the necessity of their inclusion in the Oficial List of Threatned Flora of Rio Grande do Sul.