The creation of biodiversity involves the evolution of new species. Recent trends in the study of speciation have increased the emphasis on the role of ecology in adaptation and the evolution of reproductive isolation. This includes examining the relative contributions of different types of selection, the role of gene flow and the genomic changes that occur during ecological speciation. The search for speciation genes continues, however our growing knowledge of how the genome translates into phenotypes means we should now consider a broader molecular basis of speciation, which includes genetic, transcriptomic and potentially epigenetic variation that contribute to phenotypic variation. This thesis addresses the molecular basis of speciation by using three different complementary methods to examine the early stages of ecological speciation and the evolution of premating reproductive isolation between two incipient species of the cactophilic fly, Drosophila mojavensis. First, the genetic basis was examined through the sequencing of two candidate genes underlying reproductive isolation (Chapter 2). Second, the historical biogeography of population divergence was uncovered using multiple sequenced loci (Chapter 3). Lastly, gene expression across the whole transcriptome associated with phenotypic plasticity and mating success was assessed (Chapter 4). Further, the role of epigenetic imprinting in the population divergence of a freshwater fish, Girardinichthys multiradiatus, was examined through sequencing of a well known gene involved in sexual conflict (Chapter 5). These studies find that uncovering the genetic variation underlying speciation is difficult, especially when there is extensive phenotypic plasticity. Further, gene expression plasticity may play an important role in the evolution of premating isolation, and this includes a role for epigenetic mechanisms of gene expression. Additionally, it is important to assess the demographic scenario of population divergence to put into context the ecological and functional data on divergent groups. Through these studies this thesis examines the genetic, expression and epigenetic variation associated with on-going population divergence, and emphasises the need to consider the potential role of the full range of gene expression changes during ecological speciation.

Dans ce travail de thèse, nous avons étudié le transport du fer dans la plante, en nous focalisant sur la dernière étape de circulation : le remplissage de la graine. Il nous a paru important de comprendre 1- comment le fer arrive à la graine, 2- la manière dont il est délivré à l'embryon en développement, 3- sous quelles formes et 4- où et comment il est stocké dans l'embryon. Nous avons choisi de nous appuyer sur deux espèces modèles: Pisum sativum pour les approches de biochimie et Arabidopsis thaliana pour les approches de génétique. Le pois a été choisi car ses graines sont de grande taille et ont la particularité d'accumuler un albumen liquide qui sert de soutien nutritionnel pour l'embryon. Le point de départ de ce projet est l'étude de la spéciation du fer, c'est-à-dire l'identification des ligands du fer, dans cet albumen. Sur la base de la connaissance des complexes de fer circulant jusqu'à la graine, nous avons proposé de nouvelles fonctions physiologiques. La grande taille des cellules de pois a permis d'étudier la localisation du fer et sa spéciation in situ, à l'échelle subcellulaire. Chez Arabidopsis, nous avons étudié le rôle de deux gènes candidats, potentiellement impliqués dans le transport du fer vers la graine. / In this work, we studied iron transport in plants and we focused on the last circulation step: the seed filling. It seemt important to understand 1- how iron is arriving to the seeds, 2- the way it is delivered to developping embryos, 3- in which form and 4- where and how it is stored in embryos.To adress these questions, we used two model species: Pisum sativum for biochemical approaches and Arabidopsis thaliana for genetic approaches. Pea was choosen because of the large size of its seeds, and their characteristic to accumulate a liquid endosperm that feed embryos.The project started with the study of iron speciation, meaning the identification of iron ligands, in this endosperm. On the basis of the knowledge of the iron complexes arriving to seeds, we highlighted new physiological functions. The large size of pea cells also allowed us to study iron localization and in situ speciation, at subcellular level. In Arabidopis, we studied the role of two candidate genes putatively involved in iron transport to seeds.

Distributions of toxic trace elements were studied in soils before and after disturbation of their profiles.Two areas with different vegetation cover were selected: beech (Fagus sylvatica) and spruce (Picea abies) forests at the Načetín site in the Ore Mts. In the past, this area belonged to places with extreme levels of acidic atmospheric deposition. The studied areas are not placed too far from each other and have thus approximately the same climatic conditions, geological background and pollution input. On the other hand, physicochemical properties of soils (pH, CEC, BS, Ctot, Stot) and concentrations of major and trace elements are different. At selected sites in spruce and beech stand, two soil probes to a depth of 40-50 cm were dug in 2010 and samples of individual soil horizont were collected for chemical analyses (approximately 0.5 kg). Four samples from L, H, A and B horizons were taken in the spruce forest area and five samples from L, H, A, B and C horizons were taken in the beech forest. In 2011, the sites were re-sampled and samples were taken from horizons that were disturbed in 2010, paralleled by samples of undisturbed soil horizons from the same probe sites. Trace element concentrations were determined by ICP-MS, the speciation of individual elements in the soils was determined by...

The worldwide occurrence of sites contaminated with toxic metals and the associated high costs of remediating them using chemical and mechanical methods have led to calls to develop inexpensive and sustainable approaches based on the use of plants that naturally accumulate large amounts of metals in their tissues. The ability of plants to remediate metals has been rigorously studied and some species have been identified as excellent phytoremediators. However, the growth of phytoremediators is often retarded under high soil metal concentrations, rendering them ineffective. Meanwhile, some plants do not have remediating abilities but are capable of growing in contaminated environments with little or no sign of stress. Despite the volume of research dedicated to the screening and evaluation of phytoremediators, major questions remain about why some plants survive but do not remediate while the growth of phytoremediators is mostly hindered. The growth and metal-remediating efficiency of plants exposed to toxic concentrations of metals can be enhanced by inoculating phytoremediating plants with certain bacteria but the mechanisms behind this process remain unclear. Furthermore, the use of leguminous plants to improve the growth of a target plant under a mixed planting system has long been recognised as an effective yield-enhancing cropping system. However, the possibility of a non-remediating but tolerant leguminous plant conferring metal tolerance to a phytoremediator has not been explored. This thesis reports results from repeated glasshouse and lab-based growth experiments on the phytoremediating plant Brassica juncea exposed to 400 – 600 mg Zn kg-1. The aim was to investigate the abilities of two plant growth promoting bacteria (PGPB) species Pseudomonas brassicacearum and Rhizobium leguminosarum, and a leguminous plant Vicia sativa to promote B. juncea growth and enhance remediation of Zn-contaminated soil. B. juncea plant roots were analysed using synchrotron based micro-focus X-ray Fluorescence (μXRF) imaging and X-ray Absorption Near Edge Structure (μXANES) analysis to probe Zn speciation. P. brassicacearum exhibited the poorest plant growth promoting ability, while R. leguminosarum alone and in combination with P. brassicacearum significantly enhanced B. juncea growth and Zn bioaccumulation. X-ray Absorption Spectroscopy (XAS) analysis showed that reduced plant growth was due to root accumulation of Zn as Zn sulphate, Zn oxalate and Zn polygalacturonic acids. The better growth and increased metal accumulation observed in plants inoculated with R. leguminosarum and its combination with P. brassicacearum was attributed to root storage of Zn in the chelated forms of Zn phytate and Zn cysteine. A subcellular analysis of plant root also showed that the PGPB enhanced tolerance to Zn contamination by enhancing epidermal Zn compartmentalisation depending on the nature of root colonization, and induced changes in Zn speciation to less toxic Zn species in the epidermis and endodermis of plant root. The thesis therefore identifies enhanced Zn compartmentalization at the root epidermis and bacterial mediated changes in Zn toxicity through changes in Zn speciation as key complimentary mechanisms of plant growth promotion and enhanced Zn accumulation in plants by PGPB. Further experiments investigating alternative phytoremediation strategies showed that the use of the leguminous plant V. sativa in a mixed planting system with B. juncea plants completely out performed the effects of bacteria in promoting the growth and remediation potential of B. juncea under Zn contamination. By combining PGPB with mixed planting, B. juncea recovered full growth while also achieving maximum phytoremediation efficiency. The novel legume assistedmicrobial phytoremediation method that is reported in this thesis is the first to demonstrate complete plant growth recovery in plants exposed to 400 – 450 mg kg-1 soil Zn contamination for 5 weeks. Survival of V. sativa was attributed to its root storage of Zn in the chelated forms of Zn histidine and cysteine whereas in the roots of stunted B. juncea plants the majority of Zn was present as Zn oxalate and toxic Zn sulphate. Although the use of natural and synthetic chelates has been reported to enhance phytoremediation, this thesis recommends a legume-assisted-microbialphytoremediation system as a more sustainable method for Zn bioremediation.

Sexual interactions play an important role in generating sexual selection and antagonistic co-evolution. These forces can shape differences between the sexes, but also have the potential to generate population divergence and contribute to speciation. The aim in this thesis was to provide new insights into the genes involved in different stages of female sexual interactions, using Drosophila as a model system. In chapter 2 I tested whether a candidate gene (period) that influences species-specific rhythmic characteristics in male courtship song in D. melanogaster also has a pleiotropic effect on female song preference. Using mutant and transgenic strains I found support for this. In chapter 3 I examined further how females respond to the song at the level of gene expression, using microarrays. Expression profiles revealed modest changes in transcripts abundance overall, which were dominated by antennal olfactory genes, neuropeptide encoding genes and immunity genes. Many of these have previously been found to respond to mating. In chapter 4 I therefore studied further two of these genes, TurandotM and TurandotC and their role in female post-mating fitness. Using RNA interference I found that knocking down these genes influenced immediate fecundity. In chapter 5 I focused on analysing post-mating gene expression patterns in relation to sexual selection in D. pseudoobscura using microarrays. I explored the consequences of experimental variation in female promiscuity on gene expression divergence as a whole, and in response to mating. I found large-scale expression divergence between monandrous and polyandrous females after 100 generations of experimental evolution. Experimental polyandry increased the expression of genes that show female-biased expression in wild-type individuals and decreased male- biased gene expression. Females experiencing no sexual selection showed the opposite pattern. Out of the genes affected by mating, the majority showed increased expression in polyandrous compared to monandrous females, with enrichment e.g. in oogenesis-related genes.

La région Centre Ouest du Brésil possède des massifs ultrabasiques (UB) avec des manteaux latéritiques représentants des réserves et ainsi des ressources économiques importantes de Ni. Ces massifs nickélifères permettent d’étudier le cycle du Ni sous contraintes anthropiques par une approche pluridisciplinaire, associant caractérisations chimiques, mesures physiques de sa spéciation solide, et traçage isotopique des sources et des processus affectant le nickel. Cette thèse focalisée sur l’utilisation des isotopes du Ni comme traceur a eu pour but d’identifier la signature isotopique au sein de plusieurs compartiments en interactions les uns avec les autres (roche mère, saprolite, latérite, sol et plantes) et d’associer les fractionnements observés aux processus biogéochimiques. De plus, du fait de leurs ressources économiques, les massifs étudiés, Barro Alto et Niquelândia, subissent une pression anthropique importante, minière et métallurgique. Ainsi, ils offrent une opportunité unique d’étudier le fractionnement isotopique du nickel associé à son cycle anthropique, et voir s’il est possible d’identifier la contribution anthropique dans le cycle naturel du Ni par sa signature isotopique. Les résultats ont montré que l’altération de roches UB conduit à un fractionnement isotopique du Ni, se traduisant par une perte en isotopes lourds de la phase solide, soit un Δ⁶⁰Ni de - 0,47 ‰ entre la roche mère et le top-sol. Ce fractionnement semble associé au moins en partie à l’incorporation et à la sorption des isotopes légers du Ni sur les oxydes de Fe lors de la remobilisation du Ni au cours de l’altération. Cet enrichissement en isotopes légers du Ni dans la partie solide conduit à une composition isotopique en Ni plus lourde dans la phase dissoute (eaux du massifs : 0.50 ‰ < δ⁶⁰Ni < 0,70 ‰). La zone saprolitique présente une variation importante de signature isotopique allant pour δ⁶⁰Ni de -0,04 ‰ à 1,41 ‰. Pour les échantillons présentant une signature isotopique lourde, le Ni se trouve principalement au sein de la serpentine fortement substitué, quand les signatures plus légères sont en lien avec une proportion de Ni plus importante au sein de la goethite. Dans un système comme celui-ci avec un nombre important de phases porteuses de Ni, il est cependant très difficile d’établir un lien entre la spéciation solide et l’isotopie du Ni. Le rôle des plantes dans le cycle du Ni a été abordé en étudiant le fractionnement isotopique du Ni dans trois espèces de plantes hyperaccumulatrices de Ni et deux espèces de plantes tolérantes. Il existe un fractionnement isotopique lors du transfert de Ni de la tige vers la feuille, qui est systématiquement enrichie en isotopes lourds du Ni. Les feuilles sont les compartiments des plantes où les teneurs en Ni sont les plus importantes. L’enrichissement en isotopes lourds du Ni des feuilles par rapport aux sols (- 1,05 ± 0,03 ‰ < Δ⁶⁰Ni_sol-feuilles < - 0,06 ± 0,12 ‰) semble indiquer que la restitution et la décomposition de cette matière organique au niveau du sol s’accompagnera d’un apport en isotopes lourds du Ni dans le sol. L’activité pyrométallurgique entraîne un fractionnement isotopique lors du processus de fusion en conditions réductrices qui conduit à la formation des scories de réduction. Ces résidus présentent un enrichissement en isotopes lourds (δ⁶⁰Ni = 0,18 ± 0,05 ‰) par rapport au matériel entrant (δ⁶⁰Ni = 0,08 ± 0,08 ‰) et au produit final, le FeNi (δ⁶⁰Ni = 0,06 ± 0,02 ‰). Enfin, cette étude montre que l’utilisation des isotopes du Ni pour tracer le Ni « anthropique » et le distinguer du Ni naturel possède certaines limites en raison du faible fractionnement induit par les processus pyrométallurgiques aux regards de la grande variabilité des échantillons naturels au sein de la littérature (-1.03 ‰ < δ⁶⁰Ni < 2.50 ‰). / The Centre region the West of Brazil possesses ultramafic massifs (UM) with coats lateritic representatives of the reserves and so the important economic resources of Ni. These nickelifere massifs allow to study the cycle of Ni under anthropological constraints by a multidisciplinary approach, associating chemical characterizations, physical measures, solid speciation, and the isotopic drawing of sources and the processes affecting the nickel. This work focused on the use of the isotopes of Ni as tracer aimed at identifying the isotopic signature within several compartments in interactions some with the others (source rock, saprolite, laterite, soil and plants) and to associate the fractionation observed in the biogeochemical processes. Furthermore, because of their economic resources, the studied massifs, Barro Alto and Niquelândia, undergo an important, mining and metallurgical anthropological pressure. So, they offer an opportunity to study the isotopic fractionation of the nickel associated with its anthropological cycle, and to see if it is possible to identify the anthropological contribution in the natural cycle of Ni by its isotopic signature. The results showed that the weathering of rocks UB leads to an isotopic fractionation of Ni, being translated by a loss in heavy isotopes of the solid phase with a Δ⁶⁰Ni of - 0,47 ‰ between the bedrock and the top-soil. This division seems associated at least partially with the incorporation and with the sorption of the light isotopes in iron oxides during the remobilization of Ni. This enrichment in light isotopes in the solid part leads to a heavier isotopic composition in the dissolved phase (waters of massifs: 0.50 ‰ < δ⁶⁰Ni < 0,70 ‰). The saprolitic zone presents an important variation of isotopic signature (δ⁶⁰Ni) from -0,04 ‰ to 1,41 ‰. For samples presenting a heavy isotopic signature, Ni is mainly within the serpentine strongly substituted, when the lighter signatures are in connection with a proportion of Ni more important within the goethite. In a system as this one with a significant number of Ni-bearing phases, it is however very difficult to establish a link between the solid speciation and the isotopic composition. The role of plants in the cycle of Ni was approached by studying the isotopic fractionation of Ni in three species of hyperaccumulating plants of Ni and two species of tolerant plants. There is an isotopic fractionation during the transfer of Ni between the stem and the leaf, which is systematically enriched in heavy isotopes of Ni. The leaves are the compartments of the plants where the Ni contents are the most important. The enrichment in heavy isotopes of Ni in leaves with regard to soils (- 1,05 ± 0,03 ‰ < Δ⁶⁰Ni_sol-feuilles < - 0,06 ± 0,12 ‰) seems to indicate that the return and the decomposition of this organic matter at soil level will come along with a contribution in heavy isotopes of Ni in the soil. The pyrometallurgical activity lead to an isotopic fractionation during the smelting process in reducing conditions which leads to the formaton of the reduction slag. These slags present an enrichment in heavy isotopes (δ⁶⁰Ni = 0,18 ± 0,05 ‰) compared with the feeding material (δ⁶⁰Ni = 0,08 ± 0,08 ‰) and the end product, the FeNi (δ⁶⁰Ni = 0,06 ± 0,02 ‰). Finally, this study shows that the use of the isotopes of Ni to decipher the Ni anthropogenic and natural is limited because of the low fractionation induced by the pyrometallurgical processes in the looks of the big variability of the natural samples within the literature (-1.03 ‰ < δ⁶⁰Ni < 2.50 ‰).

Alguns dos padrões ecológicos mais consistentemente encontrados na natureza, como as relações espécie-área e as distribuições de rank-abundância, podem ser previstas por uma classe de modelos neutros. Nesse contexto, neutralidade quer dizer que há equivalência demográfica entre os indivíduos de todas as espécies. Para os modelos dessa classe, extinções causadas por flutuações demográficas são contrabalanceadas por algum mecanismo de especiação. Cada modo de especiação deixa uma marca nos padrões ecológicos emergentes. Foi mostrado que um modelo com uma implementação mecanística de especiação gera padrões de diversidade que dependem de limites geográficos. Eu usei simulações baseadas em indivíduos com uma implementação mecanística de especiação para investigar se padrões espaciais intrínsecos das comunidades poderiam transformar os padrões de biodiversidade. Eu descobri que existe uma transição de fase no modo de especiação que depende da estrutura espacial da comunidade. Uma gama extensa de padrões encontrados na natureza puderam ser unificados em um único modelo dada essa transição de fase. Relações entre riqueza e idade de um clado podem ser melhor compreendidas considerando-se o efeito previsto de desaceleração crítica da diversificação. Uma nova interpretação foi dado ao efeito \"Clado Morto Andando\", característico dos períodos seguintes a extinções em massa. Uma redefinição objetiva e biologicamente razoável para especiação alopátrica é explorada, graças às propriedades da transição de fase descrita. Eu proponho a existência de um \"crédito de especiação\", e exploro suas possíveis implicações para a conservação a longo prazo da biodiversidade / Some of the most consistent ecological patterns encountered in nature, such as species-area relationships and rank-abundance distributions, can be predicted from a class of neutral models. In this context, neutrality means demographic equivalence between individuals of all species. Within this class of neutral models, species extinction by demographic fluctuations is counterbalanced by some speciation mechanism. Each particular speciation mode leaves an imprint in the resulting patterns. A model with a mechanistic speciation implementation was shown to generate patterns dependent on geographic constraints. I used individual based simulations with a mechanistic speciation implementation to investigate whether the intrinsic spatial patterning of organisms could transform biodiversity patterns. I found out that there is a phase transition on speciation modes that is dependent on the spatial structure of the community. An extended range of the biodiversity patterns found in nature can be unified into a single model because of this phase transition. Clade richness and age relationships may be understood by the predicted critical slowdowns in diversification. A new interpretation is given to the post mass extinction \"Dead Clade Walking\" effect. An objective and biologically reasonable redefinition of allopatric speciation is explored by exploiting the phase transition. I propose the \"speciation credit\" effect, and its potential implications for long term biodiversity conservation

O ferro é um nutriente essencial para quase todas as espécies vivas e desempenha muitos papéis essenciais nos sistemas biológicos, como transporte de oxigênio, respiração, metabolismo energético, destruição de peróxidos e síntese de DNA. A deficiência de ferro no organismo pode acarretar diversas desordens fisiológicas, como por exemplo, a anemia ferropriva, que está relacionada com os níveis de hemoglobinas no sangue. Uma das maneiras de se obter as necessidades diárias desse nutriente e, dessa forma evitar as desordens fisiológicas ocasionadas pela deficiência do mesmo, é o consumo de frutas, hortaliças e carnes na dieta, uma vez que esses alimentos são ricos nesse elemento. Dessa forma, foram feitas determinações para avaliar as quantidades totais e a bioacessibilidade (através de métodos in vitro) de ferro, e de outros macro e micronutrientes, em diferentes tipos de alimentos. Além disso, visando buscar correlações com os resultados obtidos, a composição centesimal e o conteúdo de ácido fítico dos alimentos analisados também foram determinados. A concentração de ferro heme foi determinada para as amostras de fígado bovino. As quantidades totais e bioacessíveis dos elementos permitiram constatar que dentre todos os alimentos analisados, o espinafre foi o alimento que apresentou a maior quantidade de ferro total, porém verificou-se que a bioacessibilidade deste nutriente é muito baixa, sendo inferior a 20%. Isto pode estar relacionado ao elevado teor de oxalatos e fitatos (que possuem capacidade complexante) presente neste tipo de alimento. Ainda com relação a bioacessibilidade deste nutriente, o fígado bovino cru foi o alimento que apresentou a maior quantidade de ferro bioacessível. Porém, quando o mesmo é submetido ao processo de cocção, o valor da bioacessibilidade deste nutriente diminui consideravelmente, o que está correlacionado com a quebra do complexo de ferro heme presente em maior parte neste alimento, transformando-se em ferro iônico, que possui uma menor biodisponibilidade no organismo humano, pois é absorvido de forma menos eficaz que o ferro heme. Além disso, com relação aos alimentos de origem vegetal, os resultados mostraram que o potássio (K) possui as maiores quantidades totais e bioacessíveis para os alimentos analisados, resultado que se encontra em concordância com o fato deste elemento ser fundamental no crescimento de qualquer espécie vegetal. A determinação do conteúdo de ácido fítico (fitatos) permitiu evidenciar que os mesmos possuem diferentes intensidades de ligação com os cátions dos nutrientes presentes nos alimentos avaliados, e desse modo a influência dos fitatos na bioacessibilidade dos elementos analisados é maior para alguns e menor para outros, dependendo da estabilidade dos complexos formados entre os minerais e os fitatos. As concentrações de ferro heme obtidas para as amostras de fígado bovino demonstraram que o aquecimento provoca uma diminuição considerável na porcentagem de ferro heme presentes nas amostras, variando entre 33 e 43 %. Esta diminuição está relacionada à clivagem oxidativa do anel porfirínico em que o Fe está coordenado, e essa redução é relativamente alta uma vez que a liberação do ferro do complexo heme só ocorre em temperaturas elevadas, de 85 a 100 °C. / Iron is an essential nutrient for almost all living species and plays essential roles in many biological systems, such as oxygen transport, respiration, energy metabolism, destruction of peroxides, and DNA synthesis. Iron deficiency in the body may cause various physiological disorders, such as anemia, which is related to hemoglobin levels in blood. One way to obtain the daily requirement of this nutrient and thus avoid the physiological disorders caused by its deficiency is to ingest fruits, vegetables, and meat, because they are rich in this element. This work evaluated the bioaccessibility (by in vitro methods) and the total amounts of iron and other macro and micronutrients in different types of food. Seeking correlations with the results, the percent composition and phytic acid content of the analyzed foods were also determined, and the concentration of heme iron in samples of bovine liver was analyzed. The total and bioaccessibles amounts of elements allowed to observe that among all foods, spinach contained the highest amount of total iron, but the bioaccessibility of this nutrient was low, below 20%, probably due to the high levels of oxalates and phytates (which have complexing capacity) in this type of food. Still regarding the bioaccessibility of this nutrient, bovine liver was the food with the highest amount of bioaccessible iron. However, cooking considerably reduced bioaccessibility of this nutrient. This decrease is correlated with the breakdown of the heme iron complex present in bovine liver, wich generated the less bioavailable and the less efficiently absorbed ionic iron. Concerning plant species, the results showed that potassium (K) had the highest total and bioaccessible amounts for the analyzed foods, a result that agreed with the fact that this element is essential for the growth of any kind vegetable. Determination of phytic acid (phytates) content showed that they correlated with the cations of the nutrients in the tasted foods differently; i. e., phytates affected the bioaccessibility of the analyzed elements to different degrees, depending on the stability of the complexes formed between the minerals present in a given food and phytic acid. The heme iron concentrations in bovine liver samples revealed that heating significantly lowered the percentage of heme iron present in the samples, which ranged from 33 to 43%. This decrease was related to the oxidative cleavage of the porphyrin ring. The reduction in heme iron was relatively large, since the release of heme iron complex only occurs at elevated temperatures from 85 to 100 ° C.

Sharks comprise a large portion of bycatch in pelagic longline fisheries worldwide. Lanthanide metals have been proposed as shark repellents. This study quantified the normalized voltage of lanthanide metals in seawater and found that there was no difference in normalized voltage among the six tested metals. Temperature and salinity had a significant effect on lanthanide normalized voltage. The output at 18ºC was significantly greater than at both 12 and 24ºC. The normalized voltage was significantly greater in freshwater than brackish or seawater. The dissolution rate for the lanthanides varied from -1.6 to -0.2g/h. As the metals dissolved the voltage remained constant. In a behavioral assay, neodymium was ineffective at repelling bonnethead sharks (Sphyrna tiburo) tested individually and in groups, and lemon sharks (Negaprion brevirostris) in groups. Due to high cost, fast dissolution rates, and lack of deterrent effects, lanthanide metals are not recommended for use in mitigating shark bycatch. / by Sara M. McCutcheon. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web.

O gênero Oligoryzomys é um dos mais complexos e diversos da subfamília Sigmodontinae e da tribo Oryzomyini. Dentre os mamíferos destaca-se por apresentar notável incongruência taxonômica, já que o número de espécies não é consenso entre os autores. Esta tese tem a finalidade de esclarecer alguns pontos conflitantes da taxonomia deste grupo e fornecer mapas atualizados da distribuição das espécies do gênero. Espero que os dados coligidos e analisados aqui possam contribuir significativamente para qualquer tentativa de revisão sistemática do Gênero no futuro. Para tanto, foram feitas comparações utilizando dados cariotípicos (2n e NFa), morfológicos e sequências do gene mitocondrial citocromo b e do íntron 7 do beta fibrinogênio. O presente trabalho está estruturado em 5 capítulos. O primeiro capítulo apresenta uma breve história da diversificação dos sigmodontíneos, uma introdução sobre o nível atual de conhecimento do gênero Oligoryzomys e por fim traz uma explanação dos aspectos filosóficos envolvidos no reconhecimento de espécie. O segundo capítulo trata dos métodos utilizados na aquisição dos espécimes em trabalhos de campo, na obtenção do material para análises citogenéticas, da extração de DNA e subsequente sequenciamento do gene mitocondrial citocromo b e do íntron 7 do beta fibrinogênio. Descreve ainda as estimativas de relacionamento filogenético, a metodologia de análise da estrutura e história populacional e como foram exploradas a variação morfológica e delimitação taxonômica. O terceiro capítulo discorre sobre aspectos citogenéticos e moleculares das espécies da Bolívia, cuja amostra foi gentilmente cedida pelo Prof. Dr. Jorge Salazar-Bravo no intuito de preencher com tais informações a lacuna existente nesta fauna. As lâminas deste material boliviano foram analisadas por mim para obter os dados brutos de cariótipo assim como todo o sequenciamento do material e posterior análises. Dentro dessa abordagem foram documentadas a variação cariotípica de algumas populações e discutidas questões taxonômicas visando responder quem são e onde estão as espécies reconhecidas para a Bolívia. O quarto capítulo visa reconhecer as espécies válidas de Oligoryzomys e estabelecer as relações filogenéticas entre elas. Neste capítulo foram testadas as hipóteses dos grupos de espécies de acordo com as propostas de Carleton e Musser (1989) e Miranda et al. (2009). A partir dos resultados obtidos foram realizadas comparações entre as espécies dos grupos, as quais, permitiram fornecer dados qualitativos capazes de auxiliar na diagnose das espécies e da sua distribuição. O quinto capítulo apresenta hipóteses dos processos e eventos envolvidos na diversificação do gênero na região Neotropical e encerra a monografia apresentando uma cronologia de diversificação das espécies estudadas. / O gênero Oligoryzomys é um dos mais complexos e diversos da subfamília Sigmodontinae e da tribo Oryzomyini. Dentre os mamíferos destaca-se por apresentar notável incongruência taxonômica, já que o número de espécies não é consenso entre os autores. Esta tese tem a finalidade de esclarecer alguns pontos conflitantes da taxonomia deste grupo e fornecer mapas atualizados da distribuição das espécies do gênero. Espero que os dados coligidos e analisados aqui possam contribuir significativamente para qualquer tentativa de revisão sistemática do Gênero no futuro. Para tanto, foram feitas comparações utilizando dados cariotípicos (2n e NFa), morfológicos e sequências do gene mitocondrial citocromo b e do íntron 7 do beta fibrinogênio. O presente trabalho está estruturado em 5 capítulos. O primeiro capítulo apresenta uma breve história da diversificação dos sigmodontíneos, uma introdução sobre o nível atual de conhecimento do gênero Oligoryzomys e por fim traz uma explanação dos aspectos filosóficos envolvidos no reconhecimento de espécie. O segundo capítulo trata dos métodos utilizados na aquisição dos espécimes em trabalhos de campo, na obtenção do material para análises citogenéticas, da extração de DNA e subsequente sequenciamento do gene mitocondrial citocromo b e do íntron 7 do beta fibrinogênio. Descreve ainda as estimativas de relacionamento filogenético, a metodologia de análise da estrutura e história populacional e como foram exploradas a variação morfológica e delimitação taxonômica. O terceiro capítulo discorre sobre aspectos citogenéticos e moleculares das espécies da Bolívia, cuja amostra foi gentilmente cedida pelo Prof. Dr. Jorge Salazar-Bravo no intuito de preencher com tais informações a lacuna existente nesta fauna. As lâminas deste material boliviano foram analisadas por mim para obter os dados brutos de cariótipo assim como todo o sequenciamento do material e posterior análises. Dentro dessa abordagem foram documentadas a variação cariotípica de algumas populações e discutidas questões taxonômicas visando responder quem são e onde estão as espécies reconhecidas para a Bolívia. O quarto capítulo visa reconhecer as espécies válidas de Oligoryzomys e estabelecer as relações filogenéticas entre elas. Neste capítulo foram testadas as hipóteses dos grupos de espécies de acordo com as propostas de Carleton e Musser (1989) e Miranda et al. (2009). A partir dos resultados obtidos foram realizadas comparações entre as espécies dos grupos, as quais, permitiram fornecer dados qualitativos capazes de auxiliar na diagnose das espécies e da sua distribuição. O quinto capítulo apresenta hipóteses dos processos e eventos envolvidos na diversificação do gênero na região Neotropical e encerra a monografia apresentando uma cronologia de diversificação das espécies estudadas.