Thesis (M.S.)--Ball State University, 2009. / Title from PDF t.p. (viewed on May 07, 2010). Includes bibliographical references (p. 30-38).

Culex pipiens, in the family Culicidae, has emerged as one of the biggest vectors for West Nile virus. It has two bioforms, pipiens and molestus, which differ from each other regarding habitat, diapause, and prey. Pipiens prefers to bite birds, and molestus prefers to bite humans. There is to some extent hybridization between the two, which creates a bridge-vector between birds and humans. One way to study the relationships and spreading of the mosquitos is using the intracellular bacteria Wolbachia pipientis which is present in at least 99% of al Culex mosquitoes. The bacteria have two fast evolving genes, pk1 and ank2 which are suitable for this. Not only are the bacteria suitable for genetics, but it is also manipulating the reproductive system of the mosquitoes through Cytoplasmic Incompatibility, which changes structures of populations and allows for the bacteria to spread fast and efficient. We wanted to investigate levels of Wolbachia in different populations, as well as if the two bioforms prefer a prey, together with mapping the relationships between populations using the two genes. We found that Wolbachia was present in all tested mosquitoes, with higher levels of it in the abdomen than in the thorax. We also found that the theory of a preferred prey was false within the tested populations, since both bioforms preferred birds. Lastly, we could identify five different strains of Wolbachia pipientis concentrated to different locations. This study has shown that Wolbachia is present in all tested mosquitoes and is a useful tool to determine relationships within and between populations. This is important to be able to gain understanding of the spread of West Nile virus and other vector borne diseases spread by Culex pipiens mosquitoes.

Access to abstract permanently restricted to Ball State community only / Access to thesis permanently restricted to Ball State community only / Department of Biology

Les Wolbachia sont des alpha-protéobactéries intracellulaires transmises verticalement de la mère aux descendants via les ovocytes. Du fait de ce mode de transmission, des stratégies de manipulation de la reproduction favorisant leur propagation ont été sélectionnées chez ces bactéries. La plus communément utilisée par Wolbachia s’appelle l’incompatibilité cytoplasmique (IC). L’IC a lieu lorsque des mâles infectés copulent avec des femelles non infectées ou infectées par des Wolbachia incompatibles et se traduit par la mort des descendants avant l’éclosion. L’IC est généralement conceptualisée comme un modèle mod/resc ou toxine/antidote dans lequel les Wolbachia présentes chez les mâles introduiraient dans les spermatozoïdes une toxine (fonction mod) qui, après la fécondation, entrainerait la mort des embryons, sauf si les Wolbachia présentes dans l’œuf produisent un antidote (fonction resc). C’est chez l’espèce de moustique Culex pipiens que la plus grande diversité de phénotypes d’IC a été décrite. Cette diversité repose uniquement sur la diversité des souches de Wolbachia hébergées par C. pipiens. Dans cette thèse, nous avons mené la première étude des mécanismes cytologiques responsables de la mort des embryons dans les croisements incompatibles chez C. pipiens. Nous avons montré que des défauts de condensation et de ségrégation de la chromatine paternelle lors de la première division embryonnaire entraînent la mort des embryons dans tous les croisements incompatibles étudiés. Ces défauts cellulaires sont les seuls observés, ce qui indique que la diversité de relations d’IC décrite chez C. pipiens ne repose pas sur une diversité de défauts cellulaires. L’étude, chez plusieurs souches de wPips, de l’opéron cidA/cidB dont l’implication fonctionnelle dans l’IC a récemment été mise en évidence chez la drosophile, nous a permis de montrer que cet opéron est amplifié et polymorphe dans tous les génomes de wPips séquencés. L’exploration des variants de cet opéron dans les génomes de Wolbachia infectant des populations naturelles de C. pipiens, à l’aide de plus de 250 lignées isofemelles, a permis d’associer de manière robuste une variation de cidB avec un changement dans le phénotype mod de certains mâles. En outre, la présence d’un variant ubiquitaire de cidA, supporte le rôle de ce gène dans la fonction resc. Ainsi, chez C. pipiens, l’opéron cidA/cidB grâce à son amplification et sa diversification est impliqué dans la diversité des phénotypes d’IC et fonctionnerait comme un système toxine-mod /antidote-resc : cidB étant impliqué dans la fonction mod et cidA dans la fonction resc. / Wolbachia are intracellular alpha-proteobacteria vertically transmitted from mothers to their offspring through oocytes. As a consequence of this transmission mode, reproductive manipulation strategies that promote bacteria spread in host populations have been selected. The most common manipulation used by Wolbachia is called cytoplasmic incompatibility (CI). CI occurs when infected males mate with uninfected or incompatible Wolbachia-infected females and results in the death of offspring before hatching. CI is generally conceptualized as a mod/resc or toxin/antidote model in which paternal Wolbachia would introduce a toxin (mod function) in sperms which would, after fertilization, induce embryonic death unless an antidote produced by maternal Wolbachia in the egg counteracts its effect (resc function). A to date unique diversity of CI phenotypes has been described in the mosquito species Culex pipiens. This diversity is based solely on the diversity of Wolbachia strains hosted by C. pipiens. In this PhD, we conducted, in C. pipiens, the first study of the cytological mechanism behind embryonic mortality in CI crosses. We showed that paternal chromatin condensation and segregation defects during the first embryonic division were responsible for embryonic death in all CI crosses. These CI defects were the only ones observed indicating that the diversity of CI phenotypes in C. pipiens is not based on a diversity of cellular mechanisms. We then studied the cidA/cidB operon in several wPip strains as the functional involvement of this operon in CI was recently demonstrated in Drosophila. We showed that this operon is amplified and polymorphic in all genomes of sequenced wPip. Investigation of cidA/cidB variants in Wolbachia genomes infecting natural populations of C. pipiens, using more than 250 isofemale lines, enabled us to reveal a robust association between cidB variations and change in mod phenotype. In addition, the presence of an ubiquitous cidA variant supports the role of this gene in the resc function. In C. pipiens, the cidA/cidB operon, through its amplification and diversification, is involved in the CI phenotypes diversity and would operate as a toxin-mod / antidote-resc system: cidB being involved in the mod function and cidA in the resc function.

<p>Meteorological&nbsp; conditions&nbsp; have&nbsp; a&nbsp; significant influence on the time of occurrence, abundance and activity of the mosquito vector. In the current context of climate change, it is of great importance to assess the&nbsp; impact&nbsp; of&nbsp; shifts&nbsp; in&nbsp; climatic&nbsp; conditions&nbsp; on&nbsp; the suitability for the establishment and annual activity of&nbsp; the&nbsp; vector&nbsp; species.&nbsp; Moreover,&nbsp; changes&nbsp; in&nbsp; the variability&nbsp; of&nbsp; meteorological&nbsp; elements&nbsp; and&nbsp; their extremes&nbsp; can&nbsp; generate&nbsp; unexpected&nbsp; changes&nbsp; in&nbsp; the mosquito&nbsp; vector&nbsp; population&nbsp; which&nbsp; in&nbsp; turn&nbsp; have&nbsp; an&nbsp; important effect on human health. One of the ways to put&nbsp; these&nbsp; causes&nbsp; and&nbsp; effects&nbsp; into&nbsp; perspective&nbsp; is&nbsp; to simulate the activity of the vector within a processbased framework which allows for the analysis of the contribution of individual factors on the different life stages of the vector. Such analysis is presented by use of&nbsp; sophisticated&nbsp; dynamical&nbsp; models&nbsp; simulating&nbsp; the characteristics of the biological population, forced by observed&nbsp; meteorological&nbsp; data,&nbsp; capturing&nbsp; the&nbsp; localmicro-environment&nbsp; of&nbsp; the&nbsp; vector&nbsp; habitat,&nbsp; and validated by the observed entomology.Numerical&nbsp; models&nbsp; are&nbsp; being&nbsp; developed&nbsp; to&nbsp; model vector&nbsp; population&nbsp; dynamics&nbsp; and&nbsp; the&nbsp; expected circulation of the virus within a closed system. Two modelling&nbsp; approaches&nbsp; are&nbsp; standardly&nbsp; applied&nbsp; to modelling vector population dynamics: Mechanistic and&nbsp; Stochastic.&nbsp; The&nbsp; advantage&nbsp; of&nbsp; mechanistic&nbsp; over<br />statistical&nbsp; models&nbsp; is&nbsp; that&nbsp; they&nbsp; can&nbsp; provide&nbsp; a deterministic&nbsp; framework&nbsp; allowing&nbsp; for&nbsp; the&nbsp; isolated evaluation of each input parameter and their effect on the modelled system. Mechanistic dynamical models are used to describe the biophysical processes or part<br />of&nbsp; the&nbsp; process&nbsp; as&nbsp; a&nbsp; response&nbsp; to&nbsp; changes&nbsp; in&nbsp; the meteorological conditions.<br />The&nbsp; work&nbsp; carried&nbsp; out&nbsp; in&nbsp; this&nbsp; thesis&nbsp; can&nbsp; be summarized as follows: (i) Analysis of the association between&nbsp; the&nbsp; most&nbsp; important&nbsp; abiotic&nbsp; drivers influencing the population dynamics, annual activity and&nbsp; time&nbsp; of&nbsp; occurrence&nbsp; of Culex&nbsp; pipiens and Aedes aegypti;&nbsp; (ii)&nbsp; Identifying&nbsp; the&nbsp; most&nbsp; important&nbsp; climatic factors and model settings as a function of climatic characteristics of the study region; (iii) Modelling the vector population dynamics and stability analysis of the&nbsp; dynamical&nbsp; system&nbsp; (iv)&nbsp; Analysis&nbsp; of&nbsp; different verification techniques and implications in terms of model&nbsp; application;&nbsp; (v)&nbsp; Feasibility&nbsp; analysis&nbsp; of<br />improving&nbsp; the&nbsp; model&nbsp; with&nbsp; a&nbsp; Land-Surface Parametrization scheme and short-range forecasting of pest population dynamics.</p> / <p>Meteorolo&scaron;ki&nbsp; uslovi&nbsp; bitno&nbsp; utiču&nbsp; na&nbsp; vreme&nbsp; pojave, brojnost&nbsp; vektora&nbsp; i&nbsp; njihovu&nbsp; aktivnost.&nbsp; U&nbsp; uslovima evidentnih promene klime, od ogromne je važnosti sagledati&nbsp; uticaj&nbsp; očekivanih&nbsp; promena&nbsp; klime&nbsp; na pogodnost&nbsp; uslova&nbsp; na&nbsp; pojavu&nbsp; izabranih&nbsp; vektora.<br />Takodje, značajne promene kolebanja meteorolo&scaron;kih elemenata&nbsp; u&nbsp; odnosu&nbsp; na&nbsp; vi&scaron;egodi&scaron;nji&nbsp; prosek&nbsp; i&nbsp; sve če&scaron;će pojave nepovoljnih vremenskih prilika dovode do neočekivanog pona&scaron;anja populacije komarca &scaron;to značajno&nbsp; utiče&nbsp; na&nbsp; kvalitet&nbsp; života&nbsp; i&nbsp; zdravlje&nbsp; ljudi. Jedini&nbsp; način&nbsp; da&nbsp; se&nbsp; sagledaju&nbsp; uzroci&nbsp; i&nbsp; posledice navedenih pojava zasniva se na simulaciji aktivnosti i&nbsp; brojnosti&nbsp; vektora&nbsp; uz&nbsp; mogućnost&nbsp; testiranja&nbsp; uticaja svakog&nbsp; pojedinačnog&nbsp; faktora.&nbsp; Ovu&nbsp; mogućnost pružaju samo visoko sofistikovani dinamički modeli koju su pro&scaron;li proces kalibracije i validacije zasnovan<br />na izmerenim vrednostima meteorolo&scaron;kih elemenata i karakteristika biolo&scaron;ke populacije.<br />Sofistikovani&nbsp; modeli&nbsp; za&nbsp; simulaciju&nbsp; dinamike populacije vektora i očekivane cirkulacije vektorskih transmisivnih bolesti se koriste sa ciljem modeliranja potencijalnog rizika od zaraze i epidemije. Modeli zasimulaciju dinamike vektora mogu da se podele na dve&nbsp; glavne&nbsp; grupe:&nbsp; Mehanističke&nbsp; i&nbsp; Statističke. Prednost&nbsp; mehanističkih&nbsp; modela&nbsp; nad&nbsp; statističkim&nbsp; je &scaron;to&nbsp; mogu&nbsp; da&nbsp; se&nbsp; koriste&nbsp; za&nbsp; evaluaciju&nbsp; uticaja izolovanog&nbsp; faktora&nbsp; na&nbsp; dinamički&nbsp; sistem&nbsp; i odgovarajuće promene brojnosti unutar svake faze u razvoju&nbsp; vektora.&nbsp; Mehanistički&nbsp; dinamički&nbsp; sistemi&nbsp; se koriste&nbsp; kako&nbsp; bi&nbsp; se&nbsp; opisao&nbsp; mehanizam&nbsp; biofizičkog procesa&nbsp; ili&nbsp; dela&nbsp; procesa&nbsp; u&nbsp; zavisnosti&nbsp; od&nbsp; forsirajuće veličine.<br />Predmet&nbsp; istraživanja&nbsp; u&nbsp; ovom&nbsp; radu&nbsp; jeste identifikovanje&nbsp; najznačajnijih&nbsp; biolo&scaron;kih&nbsp; i&nbsp; fizičkih procesa&nbsp; kao&nbsp; i&nbsp; odgovarajućih&nbsp; faktora&nbsp; koji&nbsp; utiču&nbsp; na brojnost i aktivnost vektora roda Aedes i Culex. Ciljevi istraživanja mogu da se sumiraju na sledeći način: (i)<br />analiza najznačajnijih meteorolo&scaron;kih parametara koji utiču na vreme pojave, brojnost i aktivnost vektora Aedes&nbsp; i&nbsp; Culex&nbsp; roda;&nbsp; (ii)&nbsp; definisanje&nbsp; najznačajnijih klimatskih&nbsp; faktora&nbsp; i&nbsp; stepena&nbsp; osetljivosti&nbsp; procesa&nbsp; na njih; (iii) modeliranje dinamike populacije vektora i analiza&nbsp; stabilnosti&nbsp; dinamičkog&nbsp; sistema;&nbsp;&nbsp; (iv) verifikacija&nbsp; i&nbsp; analiza&nbsp; metoda&nbsp; verifikacije&nbsp; i&nbsp; validacije dinamičkog&nbsp; modela;&nbsp; (v)&nbsp; kratkoročna&nbsp; prognoza dinamike&nbsp; populacije&nbsp; komarca&nbsp; i&nbsp; formulacija hidrolo&scaron;kog modula upotrebom SURFEX povr&scaron;inske<br />&scaron;eme sa ECOCLIMAP fiziogeografskim podacima.</p>

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisors: Jack B. Gingrich and Douglas W. Tallamy, Dept. of Entomology & Wildlife Ecology. Includes bibliographical references.

No description available.

No description available.

No description available.

Les Wolbachia sont des α-Protéobactéries endocellulaires transmises maternellement et qui manipulent la reproduction des Arthropodes pour augmenter leur transmission. Chez le moustique Culex pipiens, Wolbachia induit l'incompatibilité cytoplasmique (IC) qui se traduit par une forte mortalité embryonnaire lors de croisements entre individus infectés par des souches incompatibles de Wolbachia. Ce moustique se caractérise par une forte diversité génétique de ses Wolbachia (nommées wPip) et par des patrons d'IC complexes. Nous avons examiné les mécanismes qui façonnent la dynamique de cette association symbiotique aux niveaux génomique, phénotypique et populationnel. Nous avons montré que les souches wPip ont une origine génétique commune récente et qu'elles s'organisent en groupes génétiques présentant une structuration géographique. Nous avons mis en évidence des évènements de recombinaison entre souches wPip qui pourraient jouer un rôle majeur dans la diversité génétique des Wolbachia et dans l'évolution rapide des patrons d'IC. En croisant des lignées de moustiques d'origines géographiques diverses et infectées par des souches de différents groupes génétiques, nous avons montré que les IC (i) évoluent très rapidement chez Cx. pipiens; (ii) sont contrôlées par plusieurs déterminants génétiques, et (iii) qu'il y a une relation entre les patrons d'IC et les groupes génétiques des Wolbachia. Dans les populations naturelles, il apparaît que les IC sont contre sélectionnées au sein d'une population mais qu'une zone de contact entre populations infectées par des souches incompatibles peut se maintenir de façon stable. / Wolbachia are maternally inherited endocellular α-Proteobacteria that manipulate the reproduction of Arthropods to promote their own transmission. In the mosquito Culex pipiens, Wolbachia induce cytoplasmic incompatibility (CI) which results in high embryonic mortality in crosses between mosquitoes infected with incompatible Wolbachia strains. This mosquito is characterized by high genetic diversity of its Wolbachia (referred as wPip strains) and by complex CI patterns. We examined mechanisms that shape the dynamics of this symbiotic association at genomic, phenotypic and field population levels to understand how it evolves. We showed that wPip strains have a unique and recent evolutionary origin and that their diversity clusters into distinct genetic groups with a geographic structure. We revealed the existence of extensive recombinations among wPip strains, which could influence their adaptive dynamics by creating new wPip strains and thus allow the rapid emergence of new CI patterns. The analysis of crossing relationships between mosquito lines from different geographic origins and infected with wPip strains belonging to different genetic groups showed that CIs (i) evolve rapidly in Cx. pipiens; (ii) are controlled by several genetic factors, and (iii) there is a significant relationship between CI patterns and genetic divergence of wPip strains. In field populations, it appears that CIs are selected against within a population but a contact zone between populations infected by incompatible Wolbachia strains can be stably maintained.