Pseudomonas syringae is a common foliar plant pathogenic bacterium that causes diseases on many crop plants. We hypothesized that today's highly virulent P. syringae crop pathogens with narrow host range might have evolved after the advent of agriculture from ancestral P. syringae strains with wide host range that were adapted to mixed plant communities. The model tomato and Arabidopsis pathogen P. syringae pv. tomato (Pto) DC3000 and its close relatives isolated from crop plants were thus selected to unravel basic principles of host range evolution by applying molecular evolutionary analysis and comparative genomics approaches. Phylogenetic analysis was combined with host range tests to reconstruct the host range of the most recent common ancestor of all analyzed strains isolated from crop plants. Even though reconstruction of host range of the most recent common ancestor of all analyzed strains was not conclusive, support for this hypothesis was found in some sub-groups of strains. The focus of my studies then turned to Pto T1, which was found to represent the most common P. syringae lineage causing bacterial speck disease on tomato world-wide. Five genomes were sequenced and compared to each other. Identical genotypes were found in North America and Europe suggesting frequent pathogen movement between these continents. Moreover, the type III-secreted effector gene hopM1 was found to be under strong selection for loss of function and non-synonymous mutations in the fliC gene allowed to identify a region that triggers plant immunity. Finally, Pto T1 was compared to closely related bacteria isolated from snow pack and surface water in the French Alps. Recombination between alpine strains and crop strains was inferred and virulence gene repertoires of alpine strains and crop strains were found to overlap. Alpine strains cause disease on tomato and have relatively wider host ranges than Pto T1. The conclusion from these studies is that Pto T1 and other crop pathogens may have evolved from ancestors similar to the characterized environmental strains isolated in the French Alps by adapting their effector repertoire to individual crops becoming more virulent on these crops but losing virulence on other plants. / Ph. D.

O Estado de São Paulo apresenta uma das mais altas taxas de infecções por vírus dengue no Mundo, mas apesar dessa situação, poucos são os estudos dirigidos às populações do mosquito Aedes aegypti. O objetivo deste trabalho foi caracterizar geneticamente e morfologicamente populações de Ae. aegypti localizadas em seis municípios (Santos, S.P., Campinas, São Carlos, Catanduva, S.J.R.P.) do Estado de São Paulo durante 2011 e 2012. Todos os marcadores biológicos indicaram estruturação populacional. Os oito loci microssatélites apontaram diferenciação genética moderada entre as populações (Fst= 0.04; p < 0,05) e os níveis de diversidade nucleotídica do gene COI (&pi; =0,0062) e do gene ND4 (&pi;=0,017) foram moderadamente altos. Duas linhagens geneticamente distintas foram encontradas no Estado. Ao longo dos meses que compreenderam o estudo, foram encontradas diferenças morfo-genéticas temporais entre as seis populações analisadas, possivelmente indicativas de microevolução. Os resultados obtidos podem ser úteis para compreendermos a dispersão deste mosquito vetor. / The State of São Paulo displays one of the highest rates of dengue infection in the world, but despite this fact, a few populational studies of Ae. aegypti have been undertaken. The aim of this study was to genetically and morphologically characterize Ae. aegypti populations from six locations in the São Paulo State (Santos, S.P., Campinas, São Carlos, Catanduva, S.J.R.P.) during 2011 and 2012. The phenetic and genetic analyses revealed that populations of Ae. aegypti are structured. Eight microsatellites loci were polymorphic and genetic differentiation among samples was moderate (Fst= 0.04; p < 0.05). Nucleotide diversities of COI (&pi; = 0.0062) and ND4 gene (&pi; = 0.017) were moderately high. Two lineages distinct genetically were found in the State. Over the months comprised by the study, we found the temporal genetics and morphologics differences among the six populations, a possibly indicative of microevolution of mosquitoes. The results of this study may be useful for understand the spread of this vector mosquitoes in the State of São Paulo.

This thesis investigates the molecular evolutionary and macroevolutionary consequences of flight loss in insects. Chapter 2 tests the hypothesis that flightless groups have smaller effective population sizes than related flighted groups, expected to result in a consistent pattern of increased non-synonymous to synonymous ratios in flightless lineages due to the greater effect of genetic drift in smaller populations. Chapter 3 tests the hypothesis that reduced dispersal and species-level traits such as range size associated with flightlessness increase extinction rates, which over the long term will counteract increased speciation rates in flightless lineages, leading to lower net diversification. The wide-spread loss of flight in insects has led to increased molecular evolutionary rates and is associated with decreased long-term net diversification. I demonstrate that the fundamental trait of dispersal ability has shaped two forms of diversity—molecular and species—in the largest group of animals, and that microevolutionary and macroevolutionary patterns do not necessarily mirror each other. / Generously funded by NSERC with a Canada Graduate Scholarship and the Government of Ontario with an Ontario Graduate Scholarship to T. Fatima Mitterboeck; NSERC with a Discovery Grant to Dr. Sarah J. Adamowicz

À partir de la fin du Pléistocène, une réduction de la taille des dents humaines et une simplification morphologique ont été observées et débattues en lien avec des changements culturels et environnementaux. Suite à de nouvelles découvertes et à la révision des contextes archéologiques de certains gisements, une réévaluation de la nature des variations de plus de 1900 couronnes dentaires est proposée pour 176 individus de la fin du Paléolithique, du Mésolithique et du début du Néolithique provenant du Bassin aquitain et de ses marges. Particulièrement, les variations de la structure interne (épaisseur de l’émail, proportions des tissus dentaires, morphologie de la jonction émail-dentine) ont été évaluées de manière non invasive grâce aux méthodes d’imagerie 3D (microtomographie) et de morphométrie géométrique afin de caractériser et d’interpréter l’évolution des couronnes dentaires selon une approche intégrée. Les résultats des analyses morphométriques montrent une discontinuité entre les populations de la fin du Pléistocène et celles du début de l’Holocène. Une réduction des dimensions externes, des épaisseurs de l’émail et des proportions des tissus est mesurée entre la fin du Paléolithique et le Mésolithique, alors que des différences majeures dans les types d’usure et la distribution de l’émail sont observées entre le Mésolithique et le Néolithique. Ces données suggèrent que les modifications induites par les changements environnementaux de l’Holocène ont eu un impact plus important sur la réduction dentaire dans les populations humaines et que les changements culturels néolithiques ont surtout affecté la distribution de l’émail. Enfin, une corrélation entre le type d’usure occlusale et la distribution de l’épaisseur de l’émail a été mise en évidence et associée à des changements de régime alimentaire. En particulier, l’épaisseur de l’émail peut évoluer rapidement comme une réponse sélective aux changements fonctionnels dans la biomécanique de la mastication. / Since the Late Pleistocene, a reduction in size and a morphological simplification of human teeth have been observed and arguably linked to cultural and environmental changes. Following new discoveries along with the revision of key archaeological contexts, a re-assessment of the nature of crown variations on more than 1900 teeth is proposed for 176 Late Paleolithic, Mesolithic and Early Neolithic individuals from the Aquitaine Basin and its margins. In particular, a non-invasive assessment of internal tooth structure variability (enamel thickness, dental tissue proportions, enamel-dentine junction morphology) has been performed using 3D imaging methods (microtomography) and geometric morphometrics in order to characterize and interpret dental evolution from a whole crown perspective. Results from the morphometric analyses show a discontinuity between Late Pleistocene and Early Holocene populations. External dimensions, enamel thicknesses and tissue proportions are reduced in Mesolithic individuals compared to those of the Late Paleolithic, while major differences are observed in occlusal wear patterns and enamel distribution between Mesolithic and Early Neolithic samples. These data suggest that environmentally-driven modifications during the Early Holocene had a major impact on dental reduction in human populations and that Neolithic cultural changes had mostly affected enamel distribution. Finally, a correlation between occlusal wear pattern and enamel thickness distribution is observed and associated with dietary changes. In particular, enamel thickness may have rapidly evolved as a selective response to functional changes in masticatory biomechanics.