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<p> A new dating method has been developed which uses fission product xenon in a manner similar to radiogenic argon in the 40Ar - 39Ar method. Measurable quantities of spontaneous fission xenon accumulate with time in rocks and minerals containing approximately 1 ppm or more of uranium as a result of the spontaneous fission of 238u. In the past, attempts have been made to date this type of sample by measuring the absolute amount of fission product xenon and the uranium content. In the new method a sample is irradiated in a thermal neutron flux to implant xenon from the neutron induced fission of 235u in amounts proportional to the uranium content. After a short cooling period (before radioactive 133xe has decayed) the sample is placed in a high vacuum system and the xenon is released by heating in a series of temperature steps. For each step the isotopic composition of the xenon is measured using a high sensitivity mass spectrameter and the ratio of spontaneous fission xenon to neutron fission xenon is calculated. Fission xenon ages for all steps are then calculated from the spontaneous to neutron fission xenon ratios and the measured integrated neutron flux. </p> <p> The method has several advantages over the conventional U - Xe technique. {a) The measurement of isotope ratios is inherently more precise than the measurement of absolute quantities. (b) Whereas the conventional U - Xe technique measures the sample date only once, the method described in this thesis measures the sample date several times. (c) If a geological disturbance has caused loss of fission xenon a valid date can still be obtained using the low mobility xenon released at high temperatures. (d) In some samples disturbed dates as well as initial formation dates can be measured. </p> <p> The method was developed and evaluated by a series of experiments which dated four zircon samples, one sphene sample, and a carbonatite sample. The zircon and sphene samples had been dated in other laboratories by the conventional u - Th - Pb and Rb - Sr methods. Fission xenon dating of these samples provided valuable new geochronological information. The experiments also showed that in addition to the advantages mentioned, the new method appears to be better able to see past metamorphic events than other methods. </p> / Thesis / Candidate in Philosophy

O Pantanal da Nhecolândia, localizado no estado do Mato Grosso do Sul, é parte do Pantanal Brasileiro e possui características específicas, dentre elas a existência de lagos salinos, comumente conhecidos como Salinas. Para se estimar uma possível influência humana no Pantanal da Nhecolândia quatro perfis de sedimento foram coletados, em 2010, nas Salinas A, 6, M e V com o objetivo de se fazer a caracterização química inorgânica dos sedimentos determinando os elementos As, Ba, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb e Zn pela técnica de análise por ativação com nêutrons instrumental nas frações fina (silte + argila) e grossa (areia média + areia fina) do sedimento e também determinar as taxas de sedimentação e idade do sedimento pelo método do 210Pb. Para auxiliar na interpretação dos resultados determinou-se a composição granulométrica e o conteúdo de água das amostras de sedimento. A análise granulométrica indicou que as Salinas possuem um percentual da fração fina oscilando entre 3,5 % na Salina M a 70 % na Salina A, o que é característico dessa região. Os quatro perfis de sedimento apresentaram diferentes taxas de sedimentação, o que está provavelmente relacionado aos períodos de seca e enchentes. Os resultados obtidos de concentração dos elementos químicos foram comparados com os valores da Upper Continental Crust UCC e da North American Shale Composite NASC, e alguns elementos, como As, Hf, Rb e Sb, apresentaram valores acima destes nas duas frações granulométricas do sedimento, sugereindo à existência de depósitos naturais destes elementos nas quatro Salinas estudadas. Os resultados de concentração dos elementos estudados indicam a não existência de influência antrópica na região. Calculou-se também o fator de enriquecimento - FE dos elementos químicos usando como valores de referência os valores da UCC, NASC, e os valores da base do perfil-FEB, concluindo-se que o FEB foi a melhor metodologia para se avaliar o enriquecimento dos elementos. / Nhecolândia Pantanal, geographically located in the state of Mato Grosso do Sul, is part of the Brazilian Pantanal, and has it specific characteristics, one being the existence of saline lakes, commonly known as Salinas. Therefore, to estimate a possible human influence, a study was initiated in the Nhecolândia Pantanal in 2010, where four sediment cores were collected in Salinas A, 6, M e V. The elements As, Ba, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn were determined using instumental neutron activation analysis (INAA), in the fine (silt + clay) and coarse (medium sand + fine sand) fraction of the sediment. The sedimentation rates and age of the sediments were determined using the 210Pb method. The grain size analysis and the water content of the sediment samples were also determined to assist in the interpretation of the results. The four sediment cores showed different sedimentation rates, which is probably related to drought and flood periods. The grain size analysis showed that the Salinas have a percentage of the fine fraction oscilating from 3,5 % in Salina M to 70 % in Salina A, which is characteristic of this region. The results were compared with the values of the Upper Continental Crust - UCC and the North American Shale Composite - NASC, and some elements showed values above these, including the elements As, Hf, Rb and Sb, in the two frations of the sediment, these results of concentration of the elements in the four Salinas suggest the existence of natural deposits of these elements. The results of concentration of the studied elements in the present work suggest that there is no anthropogenic influence in the region. To evaluate these concentration values the enrichment factor - EF was calculated using reference values from the UCC, NASC and values of the core basis - BEF. It was possible to conclude that the best methodology to evaluate the elements enrichment in the Pantanal, for the present study, was the BEF.

O Pantanal da Nhecolândia, localizado no estado do Mato Grosso do Sul, é parte do Pantanal Brasileiro e possui características específicas, dentre elas a existência de lagos salinos, comumente conhecidos como Salinas. Para se estimar uma possível influência humana no Pantanal da Nhecolândia quatro perfis de sedimento foram coletados, em 2010, nas Salinas A, 6, M e V com o objetivo de se fazer a caracterização química inorgânica dos sedimentos determinando os elementos As, Ba, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb e Zn pela técnica de análise por ativação com nêutrons instrumental nas frações fina (silte + argila) e grossa (areia média + areia fina) do sedimento e também determinar as taxas de sedimentação e idade do sedimento pelo método do 210Pb. Para auxiliar na interpretação dos resultados determinou-se a composição granulométrica e o conteúdo de água das amostras de sedimento. A análise granulométrica indicou que as Salinas possuem um percentual da fração fina oscilando entre 3,5 % na Salina M a 70 % na Salina A, o que é característico dessa região. Os quatro perfis de sedimento apresentaram diferentes taxas de sedimentação, o que está provavelmente relacionado aos períodos de seca e enchentes. Os resultados obtidos de concentração dos elementos químicos foram comparados com os valores da Upper Continental Crust UCC e da North American Shale Composite NASC, e alguns elementos, como As, Hf, Rb e Sb, apresentaram valores acima destes nas duas frações granulométricas do sedimento, sugereindo à existência de depósitos naturais destes elementos nas quatro Salinas estudadas. Os resultados de concentração dos elementos estudados indicam a não existência de influência antrópica na região. Calculou-se também o fator de enriquecimento - FE dos elementos químicos usando como valores de referência os valores da UCC, NASC, e os valores da base do perfil-FEB, concluindo-se que o FEB foi a melhor metodologia para se avaliar o enriquecimento dos elementos. / Nhecolândia Pantanal, geographically located in the state of Mato Grosso do Sul, is part of the Brazilian Pantanal, and has it specific characteristics, one being the existence of saline lakes, commonly known as Salinas. Therefore, to estimate a possible human influence, a study was initiated in the Nhecolândia Pantanal in 2010, where four sediment cores were collected in Salinas A, 6, M e V. The elements As, Ba, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, K, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn were determined using instumental neutron activation analysis (INAA), in the fine (silt + clay) and coarse (medium sand + fine sand) fraction of the sediment. The sedimentation rates and age of the sediments were determined using the 210Pb method. The grain size analysis and the water content of the sediment samples were also determined to assist in the interpretation of the results. The four sediment cores showed different sedimentation rates, which is probably related to drought and flood periods. The grain size analysis showed that the Salinas have a percentage of the fine fraction oscilating from 3,5 % in Salina M to 70 % in Salina A, which is characteristic of this region. The results were compared with the values of the Upper Continental Crust - UCC and the North American Shale Composite - NASC, and some elements showed values above these, including the elements As, Hf, Rb and Sb, in the two frations of the sediment, these results of concentration of the elements in the four Salinas suggest the existence of natural deposits of these elements. The results of concentration of the studied elements in the present work suggest that there is no anthropogenic influence in the region. To evaluate these concentration values the enrichment factor - EF was calculated using reference values from the UCC, NASC and values of the core basis - BEF. It was possible to conclude that the best methodology to evaluate the elements enrichment in the Pantanal, for the present study, was the BEF.

Molecular dating (or molecular clock) is a powerful technique that uses the mutation rate of biomolecules to estimate divergence times among organisms. In the last two decades, the theory behind the molecular clock has been intensively developed, and it is now possible to employ sophisticated evolutionary models on genome-scaled datasets in a Bayesian framework. The molecular clock has been successfully applied to virtually all types of organisms and molecules to estimate timing of speciation, timing of gene duplications, and generation times: this knowledge allows contextualizing past and present events in the light of (paleo)ecological scenarios. Molecular clock studies are routinely used in evolutionary and ecological studies, but their use in applied fields such as agricultural and medical entomology is still scarce in particular because of a paucity of genome data. Genome-scaled clocks have been successfully applied, for example, to various model organisms such as Anopheles and Drosophila, as well as to invasive mosquitoes Aedes aegypti and Aedes albopictus. Many other invasive pests are emerging worldwide aided by global trade, increased connectivity among countries, lack of prevention, and flawed invasive species management. Among them, there is Aedes koreicus and Aedes japonicus, two invasive mosquito species which are monitored for public health concerns because of their harboured human pathogenic viruses. For these, as well as for other insects of societal relevance, such as the parasitoid Trissolcus japonicus, there is a paucity of gene markers and no genome data for large scale molecular clock studies. Invasive pests are typically studied using microevolutionary approaches that tackle events at an intraspecific level: these approaches provide important information for the pest management, for example, by revealing invasion routes and insecticide resistances. Approaches that tackle the deep-time evolution of the pest, such as the molecular clock, are instead less used in pest science. Many important traits associated with invasiveness have evolved by speciation over a long time frame: the molecular clock can reveal the paleo-ecological conditions that favoured these traits helping a better understanding of pest biology. Molecular clock, when coupled with phylogenomics, can further identify genes and patterns that characterize the pest: this knowledge can be used to enhance management practices. Although this is a data-driven thesis, its major aim is to provide new results to demonstrate the utility of the molecular clock in pest science. This has been done by systematically apply the molecular clock to various neglected organisms of medical and agricultural relevance. To this aim, I generated new genome data and/or assembled the largest genome-scaled data to date. I studied the molecular clock in mosquitoes, focusing on the Aedini radiation (Chapter 2) and identified a strong incongruence between the mitochondrial and nuclear phylogeny for what concerns their molecular clock. This result highlighted the importance of employing genome scaled data for these species to exclude stochastic effects due to poor/inaccurate sampling in clock studies. To tackle the absence of data, I further assembled the whole mitogenome of emerging invasive species Aedes koreicus and Aedes japonicus with the aim of producing useful data for molecular typing and of inferring divergence estimates using whole mitogenomes (Chapter 3). Dated phylogenies point toward more recent diversification of Aedini and Culicini compared to estimates from previous works, addressing the issue of taxon sampling sensitivity in dated phylogeny. Although it is possible to perform molecular clock studies on single/few gene markers, the current trend is to couple this methodology with genome-scaled datasets to reduce the stochastic effect of using few genes. For this reason, I sequenced the draft genome of A. koreicus and A. japonicus (Chapter 4). The assemblies were extremely fragmented, highlighting the problem of sequencing large genomes using short reads. The assemblies provided, however enough information for genome skimming allowing extraction of BUSCO genes for downstream analyses, whole mitogenome assemblies (used in Chapter 3), and characterisation of the associated metagenome. These data need to be integrated by long reads; it provides, however a first framework to investigate the genome evolution of these species. I further sequenced and assembled the genome of Trissolcus japonicus, the parasitoid wasp of the invasive pest Halyomorpha halys. To elucidate its divergence, estimate and define an intraspecific typing system to differentiate strains for biocontrol strategies, I reconstructed the mitochondrial genomes of two populations: the mitogenomes were surprisingly identical, suggesting that they belong to the same de facto population. I further provide a detailed clock investigation of Zika, a virus harboured and transmitted by some Aedes species (Chapter 5). Using the largest set of genomes to date, I could set the origin of ZIKV in the middle age and its first diversification in the mid-19th century. From a methodological point of view, the clocking of this virus highlighted the importance of checking for recombination and for cell-passages to obtain correct divergence estimates. I finally show my contributions to molecular clock studies of three other invasive species (Chapter 6): I helped disentangle the divergence times of Bactrocera, a genus of invasive fruit files pest of agriculture; I contributed in performing a phylogenomics study of opsin genes in Diptera; I used chloroplast and nuclear genome data to reconstruct the divergences of the invasive reed Arundo. In the various Chapters of my thesis, I highlighted the limits and the problems of current molecular clock methodologies and identified the best practices for different types of organisms in order to develop a cross-discipline understanding of the molecular clock techniques. The various results presented in this thesis further demonstrate the utility of the molecular clock approach in pest studies.

Les fibules de l’oppidum de Bibracte sont l’objet de ce travail. D’ordinaire, les fibules sont classifiées et analysées par types, mais cela pose des problèmes méthodologiques. Pour les éviter, je développe une nouvelle méthode pour construire une chronologie en général et pour dater les fibules de Bibracte en particulier. Je me fonde sur l’approche théorique de John Collis (2009) et j’adopte ainsi le concept d’horizon chronologique, qui n’a donc pas de fin et se concentre sur des caractéristiques spécifiques à la place des types. La chronologie de fibules pour le site de Bibracte se fonde sur 122 fibules stratifiées de cinq fouilles du site, datées par les autres catégories de trouvailles comme la céramique. Cette chronologie se divise en huit horizons de fibules définis par une première occurrence de 130 caractéristiques de fibules et huit combinaisons des caractéristiques. Sur cette base il est possible de dater une fibule de manière transparente et vérifiable objectivement. La datation d’une fibule peut être estimée automatiquement sur la base de données numériques ci-jointe. Cette méthode est transférable à d’autres sites et catégories de trouvailles. La chronologie des fibules de Bibracte développée dans ce mémoire de thèse permet d’observer le développement de l’occupation de Bibracte, la durée de l’utilisation de la nécropole associée et le développement de la fabrication des fibules. / This work is about the brooches from the oppidum Bibracte. Commonly brooches are classified and chronologically interpreted as types. However, inherent methodological issues are evident, in particular for today’s chronological system of the late iron age. To overcome these issues, I consider a theoretical approach by John Collis (2009), and develop a new method to construct chronologies in general and to date the brooches of Bibracte in particular. Thereby I primarily use the concept of a chronological horizon, that has only a beginning but never ends, and rather focus on brooch attributes than on types. Based on the aforementioned, I construct an alternative brooch chronology using 122 stratified brooches from five excavations in Bibracte, whose stratigraphies are dated absolute in time by ceramic finds. The herein constructed chronology consists of eight brooch horizons, that are defined by the first appearance of 130 individual brooch attributes and of eight attribute combinations. The brooch chronology obtained in this manner allows to date any brooch or fragment of a brooch replicable and inter-subjectively verifiable for future work; the brooches can be dated automatically by means of the enclosed database. Moreover, the method presented is transferable to other archaeological sites and materials. On the basis of the alternative brooch chronology of Bibracte, various results about the settlement activity of the oppidum, the utilization period of the associated cemetery and the development of the brooch production in Bibracte are obtained. / Gegenstand dieser Arbeit sind die Fibeln aus dem Oppidum Bibracte. Für gewöhnlich werden Fibeln nach Typen klassifiziert und chronologisch ausgewertet. Dies birgt jedoch methodische Probleme, die u. a. im derzeitigen Chronologiesystem der späten Eisenzeit begründet sind. Um diese Probleme zu vermeiden, entwickle ich auf der Basis eines theoretischen Ansatzes von John Collis (2009) eine neue Methode zur Konstruktion von Chronologien im Allgemeinen und zur Datierung der Fibeln von Bibracte im Besonderen. Grundlegend sind hierfür das Konzept eines chronologischen Horizontes, der nur einen Beginn hat, jedoch kein Ende, sowie die Konzentration auf Merkmale anstatt auf Typen. In diesem Sinne konstruiere ich anhand von 122 stratifizierten Fibeln aus fünf Grabungen in Bibracte, deren Stratigrafien mithilfe der Keramik absolut datiert sind, eine alternative Fibelchronologie. Diese besteht aus acht Fibelhorizonten, die durch das jeweils erste Auftreten von 130 einzelnen Fibelmerkmalen und von acht Merkmalskombinationen definiert werden. Die auf diese Weise konstruierte Fibelchronologie ermöglicht es zukünftig, Fibeln und Fibelfragmente transparent und intersubjektiv überprüfbar zu datieren sowie die Datierung mithilfe der beiliegenden Datenbank automatisch zu berechnen. Diese Methode ist auch auf andere Fundorte und Fundkategorien übertragbar. Auf der Basis der alternativen Fibelchronologie von Bibracte werden darüber hinaus u. a. Ergebnisse zur Besiedlungsgeschichte des Oppidum erzielt, zur Belegungszeit des zugehörigen Gräberfeldes und zur Entwicklung der Fibelherstellung in Bibracte.