O escudo Sul-riograndense tem sua importância econômica ligada às várias mineralizações de metais base e ouro como as áreas de Camaquã, Caçapava do Sul, Lavras do Sul e São Sepé. A região é objeto de estudos geológicos desde muito tempo e vários trabalhos já foram publicados a respeito, porém todos estes mostram grande complexidade tanto quanto à origem e evolução do escudo como para as ocorrências minerais nela presentes. O presente estudo utilizou um conjunto de análises multivariadas para dados aerogeofísicos e sensoriamento remoto em parte do Escudo do Rio Grande do Sul para verificar a contribuição destas técnicas para a otimização de recursos tanto financeiros quanto de tempo na execução dos projetos de pesquisa mineral naquela região. Os resultados mostraram que o uso destas técnicas contribui para a discriminação de grupos relacionados às litologias descritas para a área de pesquisa de forma muito mais clara que o uso das metodologias de forma individualizada. Embora não tenha revelado as assinaturas das ocorrências minerais pode ser utilizada para a discriminação destas dentro dos grupos formados pelas análises. / The Rio Grande do Sul Shield has its economic importance connected to the diverse gold and base metals mineralization that occurs in that area, such as Camaqua Basin, Cacapava, Lavras do Sul and São Sepé granitite intrusions. The region has been the subject of geological studies for a long time and several papers have been published about it, but they show great complexity for both the origin and evolution of the Shield and the mineral occurrences in it. The present study used a set of multivariate analysis for airborne geophysics and remote sensing data in part of the Rio Grande do Sul Shield, to verify the contribution of these techniques for the optimization of time and financial resources for the implementation of projects of mineral exploration. The results confirm that their use contribute to the discrimination of groups related to the described lithology in the area in a more clearly way that using these methodologies individually. Although the signatures of mineral occurrences have not been revealed, they can be used for their discrimination, based on the groups resultant from the analysis.

Submitted by Rosimeri Vergara (rosimerivergara@unipampa.edu.br) on 2018-12-11T20:02:55Z No. of bitstreams: 1 Giovani Nunes Parisi 2018 Dissertação.pdf: 4002594 bytes, checksum: 976b398edffec278577b6c3d951dfc9c (MD5) / Approved for entry into archive by Dayse Pestana (dayse.pestana@unipampa.edu.br) on 2018-12-12T12:09:44Z (GMT) No. of bitstreams: 1 Giovani Nunes Parisi 2018 Dissertação.pdf: 4002594 bytes, checksum: 976b398edffec278577b6c3d951dfc9c (MD5) / Made available in DSpace on 2018-12-12T12:09:45Z (GMT). No. of bitstreams: 1 Giovani Nunes Parisi 2018 Dissertação.pdf: 4002594 bytes, checksum: 976b398edffec278577b6c3d951dfc9c (MD5) Previous issue date: 2018 / A presente dissertação apresenta resultados petrográficos e litoquímicos de mármores calcíticos e dolomíticos coletados em quatro áreas distintas do Bloco São Gabriel, que seguem: (i) área Batovi, (ii) Área Palma; (iii) Área Passo Feio; e (iv) Área Porongos. O conjunto de mármores que afloram nessas áreas compõe um grupo mineralogicamente homogêneo. O carbonato predomina largamente sobre os outros minerais na composição modal destas rochas. Entretanto em algumas áreas, onde há minerais magnesianos como a serpentina e o talco, pode haver uma tendência a dolomitização. Após a análise e tabulação de dados das amostras de mármores calcíticos e dolomíticos, ficou estabelecido um critério prospectivo para os mármores do Bloco São Gabriel, onde foi possível separar duas populações de mármores. A primeira composta pelas áreas (i) Batovi e (ii) Palma com mármores de composição predominante Calcítica e uma segunda população de mármores predominantemente Dolomíticos, composta pelas áreas (iii) Passo Feio e (iv) Porongos. Já o estudo geoquímico, através dos Elementos Terras Raras na sequência Metassedimentar de origem carbonática, constatou que amostras apresentaram anomalias negativas de Cério e positiva de Eu. No que se refere à anomalia negativa de Ce, que ocorre devido à baixa concentração de Elementos Terras Raras da água do mar. Esta anomalia de Ce é em consequência do Ce+4e o Ce+3, terem um grande campo de estabilidade Eh-Ph. A anomalia negativa de Ce em rochas sedimentares, particularmente em rochas carbonáticas, tem sido utilizada comumente como um argumento de origem marinha, enquanto a sua inexistência é atribuída à influência de águas continentais, particularmente para rochas carbonáticas. Quanto à anomalia positiva de Eu nos sedimentos marinhos ou na água do mar, esta tem sido atribuída a um fluxo hidrotermal. / The present dissertation presents petrographic and litoquímicos results of calcitic and dolomitic marbles collected in four distinct areas of the São Gabriel Block, which follow: (i) Batovi area, (ii) Palma Area; (iii) Passo Feio Area; and (iv) Porongos Area. The set of marbles that appear in these areas make up a mineralogically homogeneous group. The carbonate predominates largely of the modal composition of these rocks. However in some areas where there are magnesian minerals such as serpentine and talc, there may be a tendency to dolomite. After analyzing and tabulating data of the samples of calcitic and dolomitic marbles, a prospective criterion was established for the marbles of the São Gabriel Block, where it was possible to separate two populations of marbles. The first one consists of the areas (i) Batovi and (ii) Palma with marbles of predominantly Calcitic composition and a second population of predominantly dolomite marbles, composed of (iii) Feio and (iv) Porongos areas. On the other hand, the geochemical study, through the Rare Earth Elements in the Metassedimentary sequence of carbonate origin, found that samples presented negative anomalies of Cerium and positive of Eu. Regarding the negative anomaly of Ce, this occurs due to the low concentration of Rare Earth Elements of sea water. This Ce anomaly is a consequence of Ce + 4e and Ce + 3, having a large Eh-Ph stability field. The negative anomaly of Ce in sedimentary rocks, particularly in carbonate rocks, has been commonly used as an argument of marine origin, while its absence is attributed to the influence of continental waters, particularly for carbonate rocks. As for the positive anomaly of Eu in marine sediments and in sea water, this has been attributed to a hydrothermal flow.

Resumo: O fenômeno da ablação é um processo que envolve o estudo de proteções térmicas, com muitas aplicações, principalmente na engenharia mecânica e aeroespacial. O processo envolve transferência de calor com movimento de fronteira, onde a posição é desconhecida a priori. As equações governantes do processo formam um sistema não-linear de equações diferenciais acoplado. A análise unidimensional do processo ablativo é realizada em um corpo de revolução, o qual está sobre intenso aquecimento. Esse problema é resolvido utilizando a Técnica da Transformada Integral Generalizada - TTIG, para solução do sistema de equações governantes. Como condição de contorno é considerada um fluxo de calor transiente no contorno, como por exemplo, o que ocorre com veículos na reentrada da atmosfera. A teoria do fluxo de calor de Tauber e de Van Driest é utilizada nessa análise. Os resultados de interesse são, a espessura e a taxa de material ablatado. Os resultados obtidos são comparados com resultados disponíveis de outras técnicas de solução em literaturas. / Abstract: The phenomenon of ablation is a process of thermal protection with several applications, mainly, in mechanical and aerospace engineering. This process involves heat transfer with a moving boundary which position is unknown a priori. The governing equations of the process are a non-linear system of coupled partial differential equations. The onedimensional analysis of ablative process has been done in a revolution body, which is on intense heating. This problem is performed by using the generalized integral transform technique - GITT for solution of the system of governing equations. As boundary condition is considered a transient heat flux like ones that occur, for example, in re-entrance of aerospace vehicles in the atmosphere. The heat flux theory of Tauber and Van Driest were used in that analysis. The results of interest are the thickness and the rate of loss of the ablative material. The obtained results are compared with available results of other techniques of solution in the literature. / Orientador: João Batista Campos Silva / Coorientador: Antonio João Diniz / Banca: Cássio Roberto Macedo Maia / Banca: Paulo Gilberto de Paula Toro / Mestre

Esta pesquisa teórica investiga o desenvolvimento da noção de couraça nos primeiros quinze anos da obra de Wilhelm Reich, de 1920 até 1935. Como objetivo central, buscamos responder a seguinte questão norteadora: qual(ais) o(s) sentido(s) de couraça no pensamento de Wilhelm Reich? Visamos, sobretudo, contribuir para o esclarecimento e a discussão dessa importante noção do pensamento reichiano. Em termos de método, a fim de acompanhar o percurso do pensamento do autor, abordamos a obra de acordo com sequência cronológica de publicação. Com essa orientação histórica, elencamos e analisamos textos que, a nosso ver, fornecem subsídios para a compreensão da noção em tela. Além disso, ficamos atentos a prováveis sinônimos e sentidos utilizados, mesmo que o termo propriamente dito não estivesse explicitamente citado. Como preparação do terreno, realizamos uma pesquisa etimológica sobre o termo couraça. Em seguida, elencamos dois autores - o filósofo francês Henri Bergson e o fundador da psicanálise Sigmund Freud - investigados devido à importância dos mesmos na construção do pensamento reichiano como um todo e, possivelmente também, em relação à noção de couraça. Em termos de resultados, os escritos de Reich analisados indicaram que as significações de couraça como defesa, proteção e resistência estão sempre presentes. Dentre os artigos acessados, localizamos a primeira aparição do vocábulo em 1922, como couraça narcísica. Constatamos que, para Reich, a couraça mantém contato com as realidades interna e externa, articula as noções de economia pulsional, ego e caráter, além de estar relacionada à operação do recalque. A princípio, é concebida na esfera psíquica, mas, gradativamente, passa a ser considerada, também, no âmbito somático, principalmente como hipertonia muscular crônica. Ainda, tecemos algumas relações com a visão de Bergson sobre o assunto e com a conceituação freudiana acerca do escudo protetor. Por fim, na esfera do tema saúde-doença, registramos algumas ponderações a respeito da relação entre a noção de couraça e o processo do desenvolvimento humano / This research examines the development of the notion of armor in the first fifteen years of Wilhelm Reich´s work, from 1920 until 1935. As the main goal, we aimed to answer the question: What is (are) the meaning(s) of the term armor in Wilhelm Reich´s thought? We had in view, above all, contribute to clear up and discuss this important notion in Reichian thought. In terms of method, in order to keep track of the author´s thinking route, we followed the chronological sequence of his publications. Based on this historical orientation, we focused and detailed the texts that, in our view, supplies subsidies for the comprehension about the notion of armor. Moreover, we drew our attention to the probable synonyms and meanings, even if the term was not cited. To begin, we researched the etymology of the term. Then, we listed two authors the French philosopher Henri Bergson and the founder of psychoanalysis Sigmund Freud investigated because of their importance on the construction of early Reich´s thought and, possibly, concerning the notion of armor. In terms of results, the analyzed Reich´s texts indicated that the significances of defense, protection and resistance are always present. Among the accessed articles, we localized the very first appearance of the word in 1922, as narcissistic armor. We verified that, to Reich, the armor keeps in contact with the inner e outer realities, articulates the notions of drive economy, ego and character, and has relations with the repression operation. In the beginning, it is conceived in the psychological sphere, but, gradually, it is considered in a somatic scope as well, especially as a chronic muscular hypertony. Yet, we wove some relations with Bergson´s view about the theme and with the freudians conception concerning the protective shield. Finally, under the health-disease angle, we pointed out some aspects and relations between the notion of armor and the human development process

Sverige genomförde vid årsskiftet 2012/2013 ytterligare en sänkning av bolagsskatten. Denna gång från 26,3 till 22 procent. Målet med sänkningen var att hamna under EU’s genomsnittliga bolagsskattenivå vilket skulle minska företags incitament till att fly Sverige för lågskatteländer. Samtidigt ville regeringen minska företagens skuldsättningsgrad. I teorin sjunker värdet på skatteskölden vid en bolagsskattesänkning och därmed också värdet på företagen. Från företagens och ägarnas perspektiv innebär sänkt skatt högre nettovinst och således en högre utdelning. Hur reagerar marknaden? Ett försök att besvara frågan görs genom att gruppera företagen efter skuldsättningsgrad och undersöka vad som händer med aktierna under den dag nyheten om bolagsskattesänkningen publiceras. Detta undersöks genom en eventstudie vilken avgränsas till Norden och andra marknader med liknande finansiellt system samt liknande lagstiftning. Till grund för undersökningen ligger aktier representerade på Stockholm OMX Large Cap. Studien finner en signifikant positivt reaktion sett till hela marknaden när nyheten om bolagsskattesänkningen blir offentlig. Vid indelning efter skuldsättningsgrad visar företagen med lägst skuldsättning den högsta positiva reaktionen, medan företagen med högst skuldsättning visar en negativ reaktion, dock inte signifikant. / At the end of 2012 Sweden implemented a further reduction in corporation tax, this time from 26.3 to 22 percent. The goal of the reduction was to reach a lower corporate tax level then the EU’s average. This would reduce the company’s incentive to flee Sweden for low-tax countries. At the same time, the Swedish Government wanted to reduce the debt ratio. In theory, the value of the tax shield is lowered and hence the value of the companies. From corporate and shareholder perspective this reduced tax means higher net income and thus a higher dividend. How does the market react? An attempt to answer this question is made by splitting the companies by leverage and examine what happened to the shares on the day the news of the company tax cut was published. This is examined through an event study, which is bounded to the Nordic countries and to other markets with similar financial systems and similar legislation. The study is based on shares represented at the Stockholm OMX Large Cap. The study finds a significant positive reaction over the entire market when the news about the corporate tax becomes public. On account of the debt-equity ratio, the firms with the lowest leverage show the highest positive response, while the companies with the highest debt show a negative reaction, however not a significant one.

Numerous glacial advances over the past 2 million years have covered the entire Canadian and Fennoscandian Shield outcrop. During glacial advance and retreat, permafrost is expected to form in front of the glacier. The question of how permafrost and freezing impact the formation and evolution of brines in natural systems may be vital to understanding the chemistry of groundwater in crystalline rocks. Investigations of groundwater conditions beneath thick permafrost can provide valuable information that can be applied to assessing safety of deep, underground nuclear waste repositories and understanding analogues to potential life-bearing zones on Mars. However, very little scientific investigation of cryogenic processes and hydrogeology deep within crystalline systems has been published. The purpose of this research is to evaluate the impacts of thick permafrost (>300m) formation on groundwater chemical and flow system evolution in the crystalline rock environment over geologic timescales. A field investigation was conducted at the Lupin Mine in Nunavut, Canada, to characterize the physical and hydrogeochemical conditions within and beneath a thick permafrost layer. Taliks, or unfrozen channels within the permafrost, are found beneath large lakes in the field area, and provide potential hydraulic connections through the permafrost. Rock matrix waters are dilute and do not appear to affect groundwater salinity. Permafrost waters are Na-Cl and Na-Cl-SO4 type, and have been contaminated with chloride and nitrate by mining activities. Sulfide oxidation in the permafrost may be naturally occurring or is enhanced by mining activities. Basal permafrost waters (550 to 570 mbgs) are variably affected by mining. The less contaminated basal waters have medium sulfate concentrations and are Ca-Na dominated. This is similar to deeper, uncontaminated subpermafrost waters, which are Ca-Na-Cl or Na-Ca-Cl type with a wide range of salinities (2.6 to 40 g•L-1). The lower salinity subpermafrost waters are attributed to dissociation of methane hydrate and drawdown of dilute talik waters by the hydraulic gradient created by mine dewatering. This investigation was unable to determine the influence of talik waters to the subpermafrost zone in undisturbed conditions. Pressures are also highly variable, and do not correlate with salinity. Fracture infillings are scarce and calcite δ18O and δ13C values have a large range. Microthermometry indicates a large range in salinities and homogenization temperatures as well, indicative of a boiling system. In situ freezing of fluids and methane hydrate formation may have concentrated the remaining fluids. Field activities at the Lupin mine also provided an opportunity to study the nature of gases within crystalline rocks in a permafrost environment. Gases were generally methane-dominated (64 to 87), with methane δ13C and δ2H values varying between -56 and -42‰ VPDB and -349 to -181 ‰ VSMOW, respectively. The gases sampled within the Lupin mine have unique ranges of chemical and isotopic compositions compared with other Canadian and Fennoscandian Shield gases. The gases may be of thermogenic origin, mixed with some bacteriogenic gas. The generally low δ2H-CH4 ratios are somewhat problematic to this interpretation, but the geologic history of the site, a metaturbidite sequence, supports a thermogenic gas origin. The presence of gas hydrate in the rock surrounding Lupin was inferred, based on temperature measurements and hydrostatic pressures. Evidence also suggests fractures near the mine have been depressurized, likely due to mine de-watering, resulting in dissipation of methane hydrate near the mine. Modeling results indicate methane hydrates were stable throughout the Quaternary glacial-interglacial cycles, potentially limiting subglacial recharge. The effects of deep permafrost formation and dissipation during the Pleistocene glacial/interglacial cycle to deep groundwaters in the Canadian Shield were also investigated by compiling data from thirty-nine sites at twenty-four locations across the Canadian Shield. Impacts due to glacial meltwater recharge and surficial cryogenic concentration of fluids, which had been previously considered by others, and in situ freeze-out effects due to ice and/or methane hydrate formation were considered. At some Canadian Shield sites, there are indications that fresh, brackish, and saline groundwaters have been affected by one of these processes, but the data were not sufficient to differentiate between mixed, intruded glacial meltwaters, or residual waters resulting from either permafrost or methane hydrate formation. Physical and geochemical data do not support the cryogenic formation of Canadian Shield brines from seawater in glacial marginal troughs. The origin and evolution of Canadian and Fennoscandian Shield brines was explored with a survey of chlorine and bromine stable isotope ratios. The δ37Cl and δ81Br isotopic ratios varied between -0.78 ‰ and 1.52 ‰ (SMOC) and 0.01 ‰ and 1.52 ‰ (SMOB), respectively. Variability of chlorine and bromine isotope ratios decreases with increasing depth. Fennoscandian Shield groundwaters tend to be more enriched than Canadian Shield groundwaters for both 37Cl and 81Br. Other sources and processes which may affect δ37Cl and δ81Br composition are also explored. Primary processes such as magmatic and/or hydrothermal activity are thought to be responsible for the isotopic composition of the most concentrated fluids at each site. Positive correlations between δ81Br, and δ37Cl with δ2H-CH4 and δ13C-CH4 were noted. At this time the cause of the relationship is unclear, and may be a result of changing redox, pH, temperature, and/or pressure conditions during hydrothermal, metamorphic, or volcanogenic processes. The data suggest solute sources and fluid evolution at individual sites would be better constrained utilizing a multi-tracer investigation of δ37Cl, δ81Br, and 87Sr/86Sr ratios comparing fluids, rocks, and fracture filling minerals (including fluid inclusions).

Numerous glacial advances over the past 2 million years have covered the entire Canadian and Fennoscandian Shield outcrop. During glacial advance and retreat, permafrost is expected to form in front of the glacier. The question of how permafrost and freezing impact the formation and evolution of brines in natural systems may be vital to understanding the chemistry of groundwater in crystalline rocks. Investigations of groundwater conditions beneath thick permafrost can provide valuable information that can be applied to assessing safety of deep, underground nuclear waste repositories and understanding analogues to potential life-bearing zones on Mars. However, very little scientific investigation of cryogenic processes and hydrogeology deep within crystalline systems has been published. The purpose of this research is to evaluate the impacts of thick permafrost (>300m) formation on groundwater chemical and flow system evolution in the crystalline rock environment over geologic timescales. A field investigation was conducted at the Lupin Mine in Nunavut, Canada, to characterize the physical and hydrogeochemical conditions within and beneath a thick permafrost layer. Taliks, or unfrozen channels within the permafrost, are found beneath large lakes in the field area, and provide potential hydraulic connections through the permafrost. Rock matrix waters are dilute and do not appear to affect groundwater salinity. Permafrost waters are Na-Cl and Na-Cl-SO4 type, and have been contaminated with chloride and nitrate by mining activities. Sulfide oxidation in the permafrost may be naturally occurring or is enhanced by mining activities. Basal permafrost waters (550 to 570 mbgs) are variably affected by mining. The less contaminated basal waters have medium sulfate concentrations and are Ca-Na dominated. This is similar to deeper, uncontaminated subpermafrost waters, which are Ca-Na-Cl or Na-Ca-Cl type with a wide range of salinities (2.6 to 40 g•L-1). The lower salinity subpermafrost waters are attributed to dissociation of methane hydrate and drawdown of dilute talik waters by the hydraulic gradient created by mine dewatering. This investigation was unable to determine the influence of talik waters to the subpermafrost zone in undisturbed conditions. Pressures are also highly variable, and do not correlate with salinity. Fracture infillings are scarce and calcite δ18O and δ13C values have a large range. Microthermometry indicates a large range in salinities and homogenization temperatures as well, indicative of a boiling system. In situ freezing of fluids and methane hydrate formation may have concentrated the remaining fluids. Field activities at the Lupin mine also provided an opportunity to study the nature of gases within crystalline rocks in a permafrost environment. Gases were generally methane-dominated (64 to 87), with methane δ13C and δ2H values varying between -56 and -42‰ VPDB and -349 to -181 ‰ VSMOW, respectively. The gases sampled within the Lupin mine have unique ranges of chemical and isotopic compositions compared with other Canadian and Fennoscandian Shield gases. The gases may be of thermogenic origin, mixed with some bacteriogenic gas. The generally low δ2H-CH4 ratios are somewhat problematic to this interpretation, but the geologic history of the site, a metaturbidite sequence, supports a thermogenic gas origin. The presence of gas hydrate in the rock surrounding Lupin was inferred, based on temperature measurements and hydrostatic pressures. Evidence also suggests fractures near the mine have been depressurized, likely due to mine de-watering, resulting in dissipation of methane hydrate near the mine. Modeling results indicate methane hydrates were stable throughout the Quaternary glacial-interglacial cycles, potentially limiting subglacial recharge. The effects of deep permafrost formation and dissipation during the Pleistocene glacial/interglacial cycle to deep groundwaters in the Canadian Shield were also investigated by compiling data from thirty-nine sites at twenty-four locations across the Canadian Shield. Impacts due to glacial meltwater recharge and surficial cryogenic concentration of fluids, which had been previously considered by others, and in situ freeze-out effects due to ice and/or methane hydrate formation were considered. At some Canadian Shield sites, there are indications that fresh, brackish, and saline groundwaters have been affected by one of these processes, but the data were not sufficient to differentiate between mixed, intruded glacial meltwaters, or residual waters resulting from either permafrost or methane hydrate formation. Physical and geochemical data do not support the cryogenic formation of Canadian Shield brines from seawater in glacial marginal troughs. The origin and evolution of Canadian and Fennoscandian Shield brines was explored with a survey of chlorine and bromine stable isotope ratios. The δ37Cl and δ81Br isotopic ratios varied between -0.78 ‰ and 1.52 ‰ (SMOC) and 0.01 ‰ and 1.52 ‰ (SMOB), respectively. Variability of chlorine and bromine isotope ratios decreases with increasing depth. Fennoscandian Shield groundwaters tend to be more enriched than Canadian Shield groundwaters for both 37Cl and 81Br. Other sources and processes which may affect δ37Cl and δ81Br composition are also explored. Primary processes such as magmatic and/or hydrothermal activity are thought to be responsible for the isotopic composition of the most concentrated fluids at each site. Positive correlations between δ81Br, and δ37Cl with δ2H-CH4 and δ13C-CH4 were noted. At this time the cause of the relationship is unclear, and may be a result of changing redox, pH, temperature, and/or pressure conditions during hydrothermal, metamorphic, or volcanogenic processes. The data suggest solute sources and fluid evolution at individual sites would be better constrained utilizing a multi-tracer investigation of δ37Cl, δ81Br, and 87Sr/86Sr ratios comparing fluids, rocks, and fracture filling minerals (including fluid inclusions).

The Guiana Shield is a sub-region of Amazonia, one of the richest areas on earth in terms of species number. It is also one of the most pristine areas and is still largely unexplored. Species number, distribution, boundaries and their evolutionary histories remain at least unclear but most of the time largely unknown. This is the case for most Anurans, a group which is recognized as threatened globally and is disappearing even from pristine tropical forests. Given the pace of forest destruction and the growing concerns about climate change it is urgently necessary to obtain a better estimate of regional biodiversity in Amazonian frogs as well as a better understanding of the origin and distribution of Anuran diversity. Furthermore, given their sensitivity to climatic conditions, amphibians are a good model to investigate the influence of paleoclimatic events on Neotropical diversification which was supposedly the driving force on biotic evolution during Pleistocene in the Guiana Shield. I first test species boundaries in two species Scinax ruber and Rhinella margaritifera. These species are widely distributed, abundant and largely recognized as species complexes. I used an original species delineation method based on the combined use of mitochondrial and nuclear DNA in phylogenetic and phylogeographic analyses. Phylogenetic analyses demonstrated the polyphyly of Scinax ruber and Rhinella margaritifera. These species consist of multiple lineages that may all merit species status. Conflicting signals of mitochondrial and nuclear markers indicated the possibility of ongoing hybridization processes. Phylogeographic analyses added further information in support of the specific status of these lineages. Our results highlight the utility of combining phylogenetic and phylogeographic methods, as well as the use of both mitochondrial and nuclear markers within one study. This approach helped to better understand the evolutionary history of taxonomically complex groups of species. The assessment of the geographic distribution of genetic diversity in tropical amphibian communities can lead to conclusions that differ strongly from prior analyses based on the occurrence of currently recognized species alone. Such studies, therefore, hold the potential to contribute to a more objective assessment of amphibian conservation priorities in tropical areas. Subsequently, I tested if these first results on cryptic species are generalisable, questioning what would potentially be a minimum estimate of the number of cryptic frog species in Amazonia and the Guiana Shield, using mtDNA with multiple complementary approaches. I also combined isolation by distance, phylogenetic analyses, and comparison of molecular distances to evaluate threshold values for the identification of candidate species among these frogs. In most cases, geographically distant populations belong to genetically highly distinct lineages that could be considered as candidate new species. This was not universal among the taxa studied and thus widespread species of Neotropical frogs really do exist, contra to previous assumptions. Moreover, the many instances of paraphyly and the wide overlap between distributions of inter- and intra-specific distances reinforce the hypothesis that many cryptic species remain to be described. In our data set, pairwise genetic distances below 0.02 are strongly correlated with geographical distances. This correlation remains statistically significant until genetic distance is 0.05, with no such relation thereafter. This suggests that for higher genetic distances allopatric and sympatric cryptic species prevail. Based on our analyses, we propose a more inclusive pairwise genetic distance of 0.03 between taxa to target lineages that could correspond to candidate species. Using this approach, we identify 129 candidate species, two-fold greater than the 60 species included in the current study. This leads to estimates of around 170 to 460 frog taxa unrecognized in Amazonia-Guianas. As a consequence the global amphibian decline detected especially in the Neotropics may be worse than realised. The Rhinella margaritifera complex is characterisized by the presence of many cryptic species throughout its wide distribution, ranging from Panama to Bolivia and almost entire Amazonia. French Guiana has long been thought to harbor two species of this group, though molecular data analysed in previous chapters indicated as many as five lineages. I tested whether morphological measurements are correlated or not with genetic data using discriminant analysis and if diagnostic characteristics among the previously determined lineages can be used to describe these new species. This is a novel integrative method which can lead to a facilitation of the description of cryptic species that have been detected by phylogenetic and/or phylogeographic studies. These analyses, combined with published data of other Rhinella species, indicated that two of these lineages represent previously unnamed species. Two of the remaining are allocable to R. margaritifera while the status of the fifth is still unclear because so far it is morphologically indistinguishable from R. castaneotica. Determining if codistributed species responded to climate change in an independent or concerted manner is a basic objective of comparative phylogeography. Species boundaries, histories, ecologies and their geographical ranges are still to be explored in the Guiana Shield. According to the refugia hypothesis this region was supposed to host a forest refugium during climatic oscillations of the Pleistocene but the causes and timing for this have been criticized. We investigated patterns of genetic structure within 18 frog species in the eastern Guiana Shield to explore species boundaries and their evolutionary history. We used mtDNA and nuclear DNA and complementary methods to compare the genetic diversity spatially and temporally. With one exception all the species studied diversified repeatedly within the eastern Guiana Shield during the last 4 million years. Instead of one Pleistocene forest refugium the Guiana Shield has probably hosted multiple refugia during late Pliocene and Pleistocene. Most of these Pleistocene refugia were probably situated on the coast of French Guiana, Amapà, Suriname and Guyana. This diversification likely resulted from forest fragmentation. Many species deserve taxonomic revisions and their ranges to be reconsidered. The local endemism of the Anuran fauna of the Guiana Shield is likely to be much higher and some areas consequently deserve more conservation efforts. Specifically I questioned whether major intraspecific diversification started before the Pleistocene and occurred within the Guiana Shield or ex situ. According to ecological characteristics of the species involved I will test different diversification hypotheses. The consequences on the diversity and the endemism of the Guiana Shield will be explored. My results demonstrate that we have been grossly underestimating local biological diversity in the Guiana Shield but also in Amazonia in general. The order of magnitude for potential species richness means that the eastern Guiana Shield hosts one of the richest frog fauna on earth. In most of the species studied high levels of mtDNA differentiation between populations call for a reassessment of the taxonomic status of what is being recognised as single species. Most species display deep divergence between eastern Guiana Shield populations and Amazonian ones. This emphasizes that the local endemism in the Guiana Shield of these zones is higher than previously recognized and must be prioritised elements taken into account in conservation planning. Nevertheless, a few other species appear widely distributed showing that widespread species do exist. This underlines the fact that some species have efficient dispersal abilities and that the frog fauna of the eastern Guiana Shield is a mixture of old Guianan endemic lineages that diversified in situ mostly during late Pliocene and Pleistocene and more recently exchanged lineages with the rest of Amazonia. Recognizing this strong historical component is necessary and timely for local conservation as these zones are likely to be irremediably modified in the near future.

The Guiana Shield is a sub-region of Amazonia, one of the richest areas on earth in terms of species number. It is also one of the most pristine areas and is still largely unexplored. Species number, distribution, boundaries and their evolutionary histories remain at least unclear but most of the time largely unknown. This is the case for most Anurans, a group which is recognized as threatened globally and is disappearing even from pristine tropical forests. Given the pace of forest destruction and the growing concerns about climate change it is urgently necessary to obtain a better estimate of regional biodiversity in Amazonian frogs as well as a better understanding of the origin and distribution of Anuran diversity. Furthermore, given their sensitivity to climatic conditions, amphibians are a good model to investigate the influence of paleoclimatic events on Neotropical diversification which was supposedly the driving force on biotic evolution during Pleistocene in the Guiana Shield. I first test species boundaries in two species Scinax ruber and Rhinella margaritifera. These species are widely distributed, abundant and largely recognized as species complexes. I used an original species delineation method based on the combined use of mitochondrial and nuclear DNA in phylogenetic and phylogeographic analyses. Phylogenetic analyses demonstrated the polyphyly of Scinax ruber and Rhinella margaritifera. These species consist of multiple lineages that may all merit species status. Conflicting signals of mitochondrial and nuclear markers indicated the possibility of ongoing hybridization processes. Phylogeographic analyses added further information in support of the specific status of these lineages. Our results highlight the utility of combining phylogenetic and phylogeographic methods, as well as the use of both mitochondrial and nuclear markers within one study. This approach helped to better understand the evolutionary history of taxonomically complex groups of species. The assessment of the geographic distribution of genetic diversity in tropical amphibian communities can lead to conclusions that differ strongly from prior analyses based on the occurrence of currently recognized species alone. Such studies, therefore, hold the potential to contribute to a more objective assessment of amphibian conservation priorities in tropical areas. Subsequently, I tested if these first results on cryptic species are generalisable, questioning what would potentially be a minimum estimate of the number of cryptic frog species in Amazonia and the Guiana Shield, using mtDNA with multiple complementary approaches. I also combined isolation by distance, phylogenetic analyses, and comparison of molecular distances to evaluate threshold values for the identification of candidate species among these frogs. In most cases, geographically distant populations belong to genetically highly distinct lineages that could be considered as candidate new species. This was not universal among the taxa studied and thus widespread species of Neotropical frogs really do exist, contra to previous assumptions. Moreover, the many instances of paraphyly and the wide overlap between distributions of inter- and intra-specific distances reinforce the hypothesis that many cryptic species remain to be described. In our data set, pairwise genetic distances below 0.02 are strongly correlated with geographical distances. This correlation remains statistically significant until genetic distance is 0.05, with no such relation thereafter. This suggests that for higher genetic distances allopatric and sympatric cryptic species prevail. Based on our analyses, we propose a more inclusive pairwise genetic distance of 0.03 between taxa to target lineages that could correspond to candidate species. Using this approach, we identify 129 candidate species, two-fold greater than the 60 species included in the current study. This leads to estimates of around 170 to 460 frog taxa unrecognized in Amazonia-Guianas. As a consequence the global amphibian decline detected especially in the Neotropics may be worse than realised. The Rhinella margaritifera complex is characterisized by the presence of many cryptic species throughout its wide distribution, ranging from Panama to Bolivia and almost entire Amazonia. French Guiana has long been thought to harbor two species of this group, though molecular data analysed in previous chapters indicated as many as five lineages. I tested whether morphological measurements are correlated or not with genetic data using discriminant analysis and if diagnostic characteristics among the previously determined lineages can be used to describe these new species. This is a novel integrative method which can lead to a facilitation of the description of cryptic species that have been detected by phylogenetic and/or phylogeographic studies. These analyses, combined with published data of other Rhinella species, indicated that two of these lineages represent previously unnamed species. Two of the remaining are allocable to R. margaritifera while the status of the fifth is still unclear because so far it is morphologically indistinguishable from R. castaneotica. Determining if codistributed species responded to climate change in an independent or concerted manner is a basic objective of comparative phylogeography. Species boundaries, histories, ecologies and their geographical ranges are still to be explored in the Guiana Shield. According to the refugia hypothesis this region was supposed to host a forest refugium during climatic oscillations of the Pleistocene but the causes and timing for this have been criticized. We investigated patterns of genetic structure within 18 frog species in the eastern Guiana Shield to explore species boundaries and their evolutionary history. We used mtDNA and nuclear DNA and complementary methods to compare the genetic diversity spatially and temporally. With one exception all the species studied diversified repeatedly within the eastern Guiana Shield during the last 4 million years. Instead of one Pleistocene forest refugium the Guiana Shield has probably hosted multiple refugia during late Pliocene and Pleistocene. Most of these Pleistocene refugia were probably situated on the coast of French Guiana, Amapà, Suriname and Guyana. This diversification likely resulted from forest fragmentation. Many species deserve taxonomic revisions and their ranges to be reconsidered. The local endemism of the Anuran fauna of the Guiana Shield is likely to be much higher and some areas consequently deserve more conservation efforts. Specifically I questioned whether major intraspecific diversification started before the Pleistocene and occurred within the Guiana Shield or ex situ. According to ecological characteristics of the species involved I will test different diversification hypotheses. The consequences on the diversity and the endemism of the Guiana Shield will be explored. My results demonstrate that we have been grossly underestimating local biological diversity in the Guiana Shield but also in Amazonia in general. The order of magnitude for potential species richness means that the eastern Guiana Shield hosts one of the richest frog fauna on earth. In most of the species studied high levels of mtDNA differentiation between populations call for a reassessment of the taxonomic status of what is being recognised as single species. Most species display deep divergence between eastern Guiana Shield populations and Amazonian ones. This emphasizes that the local endemism in the Guiana Shield of these zones is higher than previously recognized and must be prioritised elements taken into account in conservation planning. Nevertheless, a few other species appear widely distributed showing that widespread species do exist. This underlines the fact that some species have efficient dispersal abilities and that the frog fauna of the eastern Guiana Shield is a mixture of old Guianan endemic lineages that diversified in situ mostly during late Pliocene and Pleistocene and more recently exchanged lineages with the rest of Amazonia. Recognizing this strong historical component is necessary and timely for local conservation as these zones are likely to be irremediably modified in the near future.

Thesis (D.P.H.)--University of Michigan.