Au niveau des marges continentales, et plus particulièrement dans des zones dites d'émissions de fluides froids, des communautés microbiennes et animales complexes se développent localement à la surface des sédiments. Ces communautés utilisent pour leur croissance des composés chimiques réduits (H2S, Méthane, CO2 ...), contenus dans un fluide à basse température, percolant à travers les sédiments et issus de phénomènes géologiques et de divers processus microbiens. Afin d'étudier la diversité des communautés microbiennes associées à ces écosystèmes ainsi que leur rôle dans l'environnement, et d'appréhender les paramètres environnementaux influençant la distribution et l'écophysiologie de ces communautés, des sédiments de surface (0-20 cm) mais également plus profonds (<9 mbsf) ont été prélevés au niveau de la Marge de Sonora. Les communautés microbiennes présentes ont été étudiées par diverses approches de biologie moléculaire, de mise en culture et de microscopie. Ce travail de recherche a permis : i) de déterminer la structure et la diversité des communautés microbiennes métaboliquement actives dans ces sédiments, ii) de mettre en évidence des écophysiologies différentes entre les acteurs du cycle du méthane (méthanogènes, ANMEs, SRB), prépondérant dans cet écosystème et iii) de découvrir la présence de nouvelles lignées et fonctions microbiennes dans les sédiments de zones d'émission de fluides froids des marges continentales. / At continental margins, and more particularly in cold seep areas, microbial and animal communities were locally detected at the surface of the sediments. These communities grow using reduced chemical compounds (H2S, Methane, COZ ...) contained in the percolated cold fluids and produced by both geological and microbial processes. ln order to study microbial community diversity in these ecosystems and their role in the environment as well as to understand the environmental factors influencing the distribution and ecophysiology of these communities, surface (0-20 cmbsf) but also deeper (<9 mbsf) sediments were collected at the Sonora Margin. Microbial communities have been studied using various molecular, cultural and microscopy approaches. This research allowed: i) to determine the structure and diversity of metabolically active microbial communities in sediments, ii) to highlight different ecophysiologies for methane cycling microorganisms (methanogens, ANME, SRB) and iii) to discover the presence of new microbial lineages and functions in the cold seeps sediments of the continental margins.

<p>Sagledavanje ukupnog genetičkog i fenotipskog diverziteta i evolucionog potencijala vrste E. tenax izvr&scaron;eno je analizom jedinki poreklom sa 42 područja Evrope, Australije, Severne i Južne Amerike i laboratorijske kolonije iz &Scaron;panije. Analiza intraspecijske varijabilnosti vrste E. tenax izvr&scaron;ena je kvantifikovanjem varijacija u veličini i obliku krila 1653 jedinke i obojenosti abdomena 936 jedinki. Analiza genetičkog diverziteta na nivou polimorfizma nukleotidnih sekvenci mtDNK je izvr&scaron;ena kod 58 jedinki, dok je analiza alozimske varijabilnosti obuhvatila 821 jedinku prirodnih populacija i laboratorijske kolonije vrste E. tenax. Rezultati su ukazali da inbriding i stohastički procesi utiču na redukciju genetičkog diverziteta i da &ldquo;oslobađaju&rdquo; skrivenu genetičku varijabilnost koja je povezana sa fenotipskom diferencijacijom. Vremenska distribucija fenotipskog diverziteta vrste E. tenax je kvantifikovana analizom jedinki četiri alohrona uzorka poreklom sa lokaliteta Venac, Fru&scaron;ka gora. Mali stepen genetičke i fenotipske diferencijacije između durmitorskih uzoraka vrste E. tenax ukazuje na odsustvo prostorne substruktuiranosti i njihovu međusobnu povezanost intenzivnim protokom gena. Analiza konspecifičkih populacija vrsta E. tenax ukazala je na odsustvo jasne međupopulacione diferencijacije na osnovu parametrara krila i molekularnih markera (alozimski lokusi i COI mtDNK), te se može zaključiti da postoji intenzivan protok gena koji elimini&scaron;e razlike između populacija. Registrovan je polni dimorfizam u veličini i obliku krila i obojenosti abdomena. Uočeno je da mužjaci u proseku imaju manja i uža krila i svetlije obojene abdomene od ženki. Analizom fenotipske diferencijacije u karakterima abdomena na uzorcima vrste E. tenax sakupljenim duž geografskog gradijenta Evrope je utvrđeno odsustvo promena po tipu kline. Dobijeni rezultati omogućavaju preciznije sagledavanje intra- i interpopulacione varijabilnosti ovog takona i ukazuju da vrsta E. tenax ima visok evolucioni potencijal za adaptacije na sredinske promene</p> / <p>This paper examines molecular and phenotypic variability in the widely spread hoverfly species Eristalis tenax. We compared 42 samples from Europe, Australia North and South America, with the aim of obtaining insights into the temporal and spatial variations and sexual dimorphism in the species. Additionally, wild specimens from Spain were compared with a laboratory colony reared on artificial media. The integrative approach was based on allozyme loci, cytochrome c oxidase I mitochondrial DNA, morphometric wing parameters (shape and size) and abdominal colour patterns. Our results indicate that the fourth and eighth generations of the laboratory colony show a severe lack of genetic diversity compared to the figures observed in natural populations. Reduced genetic diversity in subsequent generations of the laboratory colony was found to be linked with phenotypic divergence. The distribution of genetic diversity at polymorphic loci indicated genetic divergence among collection dates from Fru&scaron;ka Gora Mt, and landmark-based geometric morphometrics revealed significant wing shape variation throughout the year. Phenotypic differentiation in abdominal pattern of the E. tenax populations along latitudinal gradient Europe has not been established. Consistent sexual dimorphism was observed, indicating that male specimens had lighter abdomens and smaller and narrower wings than females. It is reasonable to assume high mobility of the dronefly and high rate of gene flow reflected the similarity of genetic and phenotypic diversity of otherwise geographically distinct populations. Hence, the present study expands our knowledge of the genetic diversity and phenotypic variability of E. tenax. The quantification of such variability represents a step towards the evaluation of the adaptive potential of this species of medical and epidemiological importance.</p>