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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

L'ontogénèse de la reconnaissance des compagnons du nid chez les fourmis et les guêpes sociales / The ontogeny of nestmate recognition in ants and social wasps

Signorotti, Lisa 16 May 2014 (has links)
Chez les insectes sociaux, la capacité à reconnaître les compagnons du nid des autres a évolué du fait de l’intérêt à distinguer les individus apparentés. En effet, il est avantageux que les actes de coopération soient uniquement dirigés vers les individus apparentés. La faculté de discrimination repose sur la capacité à percevoir les signaux de reconnaissance (hydrocarbures cuticulaires) d'un individu rencontré et de le comparer avec une représentation de l'odeur de sa propre colonie. L'ontogénèse de la reconnaissance des compagnons du nid et les processus d'apprentissage qui pourraient les sous-tendre ont été peu explorés jusqu’à ce jour. Il a été suggéré que les insectes sociaux apprennent l'odeur de leur colonie pendant les premières étapes de la vie adulte. L'objectif de ce travail était de rechercher les principales caractéristiques de l'ontogénèse du processus de reconnaissance avec une approche comparative, en utilisant deux modèles : les fourmis et les guêpes sociales. Nous avons montré que le mécanisme général de reconnaissance proposé pour le genre Polistes ne s'appliquait pas à la guêpe P. dominula. Nous avons étudié les mécanismes alternatifs, suggérant l'apprentissage pré-imaginal et le mécanisme d'auto-référence. Nous avons mis en évidence pour la première fois que la fourmi Aphaenogaster senilis apprenait, durant la vie larvaire, des signaux l'importance possible de processus cognitifs précédemment négligés tels que chimiques importants pour la reconnaissance. Ainsi, l’existence et la fonctionnalité de la mémoire larvaire ont été révélées chez les fourmis, élargissant nos connaissances sur les mécanismes de reconnaissance des compagnons du nid, l'apprentissage et la mémoire. / In social insects the ability to recognize nestmates from non‐nestmates evolved as a result of the advantages of distinguishing related individuals. Indeed, are gained only if cooperative acts are directed towards realtives. This discrimination ability relies on the capacity of perceiving recognition cues (cuticular hydrocarbons) of an encountered individual and of comparing them with a neural representation of the own colony odour. Relatively little is known about the ontogeny of nestmate recognition, and the learning processes that might be involved. It has been suggested that social insects learn their colony odour during the early stages of adult life. The overall aim of the present work was to investigate the main features of the ontogeny of nestmate recognition process with a comparative approach, using two different models: ants and social wasps. In particular, I investigated wheter general recognition mechanism proposed for the Polistes genus applies to Polistes dominula and I found that this is not the case. I studied alternative mechanisms and provided novel insights into the ontogeny of nestmate recognition in social wasps, suggesting the possible importance of previously neglected cognitive processes, such as pre-imaginal learning and self-reference phenotype matching. In ants, I showed for the first time that Aphaenogaster senilis learn chemical cues important for adult nestmate recognition during the larval life, thus larval memory is something present and functional in ants. This result gives significant insight for the study of nestmate recognition, the mechanisms at the basis, learning and memory in ants, opening new questions concerning interesting phenomena as pre-imaginal learning.
2

Sócio-etologia dos agregados coloniais de Polistes satan Bequaert, 1940: fenologia, mediadores comportamentais e sinalização química (Hymenoptera, Vespidae, Polistinae / Socio-ethology of colonial agregates of Polistes satan Bequaert, 1940: phenology, behavioral mediators and chemical signalling (Hymenoptera, Vespidae, Polistinae).

Ivelize Cunha Tannure Nascimento 20 December 2006 (has links)
O gênero Polistes é considerado um grupo modelo para a compreensão da sociobiologia das interações de dominância/subordinação em animais invertebrados, devido à pequena diferenciação de castas que resulta em um alto potencial de conflitos reprodutivos entre os membros da colônia. A construção de ninhos satélites e os seus efeitos na estrutura colonial de algumas espécies de Polistes, constituem um campo de estudo de interesse para a área da evolução do comportamento social. Neste estudo foram quantificados os padrões sazonais do desenvolvimento e a composição colonial, bem como a relação desses padrões com a variação climática sazonal. Foram também comparadas as relações que determinam a hierarquia de dominância em colônias de P. satan em relação a um modelo teórico proposto para uma hierarquia linear de dominância. Além disso, mostramos os padrões de interações agonísticas entre indivíduos que compõem a hierarquia e suas inter-relações em colônias não manipuladas e manipuladas (remoção da dominante). Foram também analisados padrões de comunicação visual (marcas de dominância) e química (hidrocarbonetos cuticulares). Os resultados mostraram que fêmeas dominantes em colônias em pré-emergência apresentaram padrões de pigmentação cefálica e perfis de hidrocarbonetos cuticulares significativamente distintos das fêmeas subordinadas ou substitutas. Os aspectos relacionados à comunicação química e visual e suas implicações biológicas são discutidas. / The genus Polistes is an organism model to understand the sociobiology in invertebrates. This group presents low caste differentiation that result in potencial reproductive conflicts between nestmates. The construction os satellite nests and their effects on the colonial structure in some Polistes are an interesting topic to the evolution of socail behavior. In this study we quantify the seasonal patterns of nest development and thei composition. We analyzed the relationship between these patterns and climatic variation. The aspects related to the hierarchy of dominance in P. satan were compared to a theoretical model that predicts a dominance hierarchy im equilibrium. In addition, we presented the agressive interaction between individuals composing a hierarchy in experimental (dominant removal) and control colonies. Patterns of both visual (dominance labels) and chemical communication (cuticular hydrocarbons) were also verified in P. Satan. Dominant females from pre-emergence colonies present both distinct patterns of cephalic pigmentation and cuticular hydrocarbons than other females. These aspects involved with the sociobiology of Polistes and their biological implications are discussed in this study.
3

The Genetic Limits to Trait Evolution for a Suite of Sexually Selected Male Cuticular Hydrocarbons in Drosophila Serrata

Sztepanacz, Jacqueline L.P. 14 November 2011 (has links)
Directional selection is prevalent in nature yet phenotypes tend to remain relatively constant, suggesting a limit to trait evolution. The genetic basis of evolutionary limits in unmanipulated populations, however, is generally not known. Given widespread pleiotropy, opposing selection on a focal trait may arise from the effects of the underlying alleles on other fitness components, generating net stabilizing selection on trait genetic variance and thus limiting evolution. Here, I look for the signature of stabilizing selection for a suite of cuticular hydrocarbons (CHCs) in Drosophila serrata. Despite strong directional sexual selection on CHCs, genetic variance differed between high and low fitness individuals and was greater among the low fitness males for seven of eight CHCs. Univariate tests of a difference in genetic variance were non-significant but have low power. My results implicate stabilizing selection, arising through pleiotropy, in generating a genetic limit to the evolution of CHCs in this species.
4

The Genetic Limits to Trait Evolution for a Suite of Sexually Selected Male Cuticular Hydrocarbons in Drosophila Serrata

Sztepanacz, Jacqueline L.P. 14 November 2011 (has links)
Directional selection is prevalent in nature yet phenotypes tend to remain relatively constant, suggesting a limit to trait evolution. The genetic basis of evolutionary limits in unmanipulated populations, however, is generally not known. Given widespread pleiotropy, opposing selection on a focal trait may arise from the effects of the underlying alleles on other fitness components, generating net stabilizing selection on trait genetic variance and thus limiting evolution. Here, I look for the signature of stabilizing selection for a suite of cuticular hydrocarbons (CHCs) in Drosophila serrata. Despite strong directional sexual selection on CHCs, genetic variance differed between high and low fitness individuals and was greater among the low fitness males for seven of eight CHCs. Univariate tests of a difference in genetic variance were non-significant but have low power. My results implicate stabilizing selection, arising through pleiotropy, in generating a genetic limit to the evolution of CHCs in this species.
5

The Genetic Limits to Trait Evolution for a Suite of Sexually Selected Male Cuticular Hydrocarbons in Drosophila Serrata

Sztepanacz, Jacqueline L.P. 14 November 2011 (has links)
Directional selection is prevalent in nature yet phenotypes tend to remain relatively constant, suggesting a limit to trait evolution. The genetic basis of evolutionary limits in unmanipulated populations, however, is generally not known. Given widespread pleiotropy, opposing selection on a focal trait may arise from the effects of the underlying alleles on other fitness components, generating net stabilizing selection on trait genetic variance and thus limiting evolution. Here, I look for the signature of stabilizing selection for a suite of cuticular hydrocarbons (CHCs) in Drosophila serrata. Despite strong directional sexual selection on CHCs, genetic variance differed between high and low fitness individuals and was greater among the low fitness males for seven of eight CHCs. Univariate tests of a difference in genetic variance were non-significant but have low power. My results implicate stabilizing selection, arising through pleiotropy, in generating a genetic limit to the evolution of CHCs in this species.
6

Regulation of reproduction in polygynous ants (Dolichoderinae): Queen fertility signal and adult polyploidy/Régulation de la reproduction de fourmis polygynes (Dolichoderinae): Signal royal de fertilité et polyploïdie des adultes

Cournault, Laurent 29 May 2009 (has links)
Regulation of reproduction is one central feature of social life. In particular, only a few individuals are in charge of producing offspring in eusocial species. This division of the reproductive labour is mainly mediated by pheromones emitted by the queens in social insects. These queen pheromones may signal the presence of a fertile queen so that workers react accordingly by taking care of her and not reproducing. Here I investigated two aspects of the reproduction of two polygynous ant species. The first one, Linepithema humile, is a unicolonial, highly polygynous and invasive species. It has been the focus of numerous studies about queen pheromones; in particular, it has been reported that queen cuticular hydrocarbons (CHC) profile is related to queen fertility. The other one, Tapinoma erraticum, is a multi-colonial, weakly polygynous and native species. Workers can lay haploid eggs in the absence of the queens which is impossible for Linepithema workers. The major part of my thesis dealt with the queen fertility signalling issue. In the first two chapters I demonstrate the link between queen fertility and queen pheromone output. I first study a queen releaser pheromone, the queen retrieval behaviour. This behaviour is performed by the workers who lay a chemical trail toward a queen located outside the nest. I successfully show this behaviour to be related to queen fertility, and not mating status, in L. humile and T. erraticum since only fertile queens (mated or not) induce such recruitment. I then highlight the role of queen fertility in the prevention of worker reproduction in T. erraticum. Again, mated fertile queens and unmated fertile queens are both able to induce such primer effect. In a third chapter I report that CHC profiles may discriminate female castes (workers, queens, virgin queens, and virgin egg-laying queens) in T. erraticum. Finally, chapter 4 summarizes my attempts to prove that CHC may be involved in queen retrieval or queen attraction. None of the various bioassays tested allows me to demonstrate the putative role of CHC as queen pheromone. In a second part, I was interested in the consequences of sex determination in T. erraticum. Chapter 5 presents the flow cytometry methodology (FC) which allowed me to score the number of sperm cells from spermathecae of several ant species, and to demonstrate that polygynous species (such as L. humile and T. erraticum) store less sperm than monogynous ones. FCM also allows determining the ploidy of sperm and adult somatic cells and chapter 6 which presents a large survey on the ploidy level within the species T. erraticum. This species displays diploid males that may produce diploid sperm which in turn can father a viable triploid female progeny. I report differences in the frequency of triploidy among female castes, the proportion of triploid workers being more important than triploid virgin queens whereas I never observed triploid mated fertile queens. Such results greatly suggest a putative regulatory mechanism involved in the rearing of triploid females. In the last chapter I investigated two populations that differ in the occurrence of triploid workers. I report these populations to vary in the number of queens and workers per nest. /La régulation de la reproduction est un aspect essentiel de la vie sociale. En particulier, chez les espèces eusociales, seuls quelques individus sont impliqués dans la production de la descendance. Dans les sociétés d’insectes, une telle division du travail reproducteur est principalement assurée par l’émission de phéromones par les reines. Ces phéromones royales renseignent les membres de la colonie sur la présence d’une reine fertile, de telle sorte que les ouvrières réagissent en s’occupant d’elle et en s’abstenant de se reproduire. Au cours de ce travail, je me suis intéressé à deux aspects de la reproduction au sein de deux espèces de fourmis polygynes. La première espèce, Linepithema humile, est invasive, unicoloniale et hautement polygyne dans les régions à climat méditerranéen. Elle a fait l’objet de nombreuses études portant notamment sur les phéromones royales. En particulier, il a été montré que le profil d’hydrocarbures cuticulaires (HCC) des reines est corrélé à leur fertilité. La seconde espèce, Tapinoma erraticum, est une espèce indigène, multi-coloniale et faiblement polygyne. Ses ouvrières sont capables de pondre des œufs mâles en absence de reines, ce dont sont incapables les ouvrières de Linepithema. Je me suis principalement intéressé à la question de la signalisation de la fertilité des reines. Dans les deux premiers chapitres, je démontre le lien existant entre la fertilité des reines et la production de phéromone royale. J’ai d’abord étudié une phéromone incitatrice (releaser) qui provoque un recrutement royal. Ce comportement collectif très caractéristique correspond à la mise en place d’une piste chimique en direction d’une reine découverte par les ouvrières en dehors du nid. Je montre que ce comportement est lié à la fertilité de la reine chez les espèces L. humile et T. erraticum car seules les reines fertiles (fécondées ou non) sont capables de d’induire le recrutement royal. Je mets ensuite en évidence le rôle de la fertilité des reines dans la régulation de la reproduction des ouvrières de T. erraticum. A nouveau, les reines fécondées fertiles et les reines vierges fertiles sont toutes deux capables d’induire un même effet déclencheur (primer), en l’occurrence, l’inhibition de la reproduction des ouvrières. Dans un troisième chapitre, je montre que les profils d’hydrocarbures (HCC) permettent de distinguer sans ambiguïté les différentes castes femelles (ouvrières, reines fertiles, reines vierges et reines vierges pondeuses) chez T. erraticum. Enfin, le chapitre 4 résume mes tentatives pour démontrer le rôle des HCC dans les phénomènes de recrutement royal ou d’attractivité des reines. Aucun des bio-essais réalisés ne me permet de démontrer l’implication des HCC dans la phéromone royale. Dans une seconde partie, je me suis intéressé aux conséquences du déterminisme du sexe chez T. erraticum. Le chapitre 5 présente cytométrie de flux (CF), une méthode qui me permet de compter les spermatozoïdes stockés dans les spermathèques de quelques espèces de fourmis et de montrer que les reines des espèces polygynes (telles que L. humile et T. erraticum) stockent moins de sperme que les espèces monogynes. La CF permet aussi de déterminer le niveau de ploïdie des cellules spermatiques ou somatiques chez l’adulte. Je me sers de cette application dans le chapitre 6 afin d’étudier le niveau de ploïdie au sein de l’espèce T. erraticum. Je montre que, dans les populations étudiées, il existe des mâles diploïdes et que ces mâles peuvent produire du sperme diploïde fertile, capable d’engendrer une descendance femelle triploïde. Je note des différences dans la fréquence des femelles triploïdes : la proportion d’ouvrières triploïdes est significativement plus importante que celle des reines vierges triploïdes. De plus, je n’ai jamais observé la présence de reines fécondées fertiles triploïdes. De tels résultats suggèrent fortement la présence d’un phénomène de régulation au cours de l’élevage du couvain triploïde. Dans le dernier chapitre, j’ai étudié deux populations de T. erraticum qui diffèrent au niveau de la proportion d’ouvrières triploïdes. Ces populations présentent des différences significatives dans le nombre de reines et d’ouvrières par nid.
7

The role of cuticular hydrocarbons in determining male reproductive success

Lane, Sarah Marie January 2016 (has links)
Cuticular hydrocarbons (CHCs) are found on the outer cuticle of all terrestrial arthropods. Although their primary function is in desiccation prevention, these compounds have also been shown to play a variety of roles in insect chemical communication, from species and sex recognition to providing cues of dominance and attractiveness. However, despite growing evidence of their versatility as cues, our knowledge of how CHCs are used in mating interactions is limited to Drosophila and field crickets. In this thesis I investigate the roles CHCs play in interactions at each stage of the mating process in the broad-horned flour beetle Gnatocerus cornutus. I assess the relative importance of CHCs in influencing male reproductive success and examine the complex interplay between different episodes of selection and the mechanisms of sexual selection acting on males. I use a combination of behavioural assays, experimental manipulations and gas chromatography. First, I identify the role of CHCs as cues of sperm competition risk and intensity, demonstrating how the presence of male-derived CHCs on the cuticles of virgin females elicits males to adjust their pre- and post-copulatory investment (chapter 2), by providing information on the state of their competitive environment. I then go on to look at the stability of CHCs as cues of sperm competition over time, finding that they are highly sensitive to environmental degradation (chapter 3) and do not persist in the habitat substrate of this species. Next, I investigate how male CHCs determine fighting and mating success. By estimating and comparing the strength and form of sexual selection imposed by male-male competition and female mate choice, I show that male CHCs are subject to strong antagonistic sexual selection (chapter 4). By experimentally manipulating male CHC profile, I then attempt to verify the selection gradients estimated for female choice 3 (chapter 5). However, my experimental manipulation fails to verify the importance of male CHCs for female mate choice. Finally, I explore the role of same-sex sexual behaviour (SSB) in determining male reproductive success (chapter 6). I find evidence to suggest that SSB may in fact be a form of aggression in its own right, and demonstrate that SSB and fighting may provide equivalent means for males to overcome female choice and secure a mating advantage. My results indicate that CHCs play key roles as chemical cues throughout the mating process and significantly impact male reproductive success. My thesis reveals the intricate nature of the relationships between mechanisms of sexual selection, alongside highlighting the need to consider both the social and physical environment when investigating the importance of chemical cues. I discuss the implications of these results for the evolution of male CHCs and how my findings can be used to further our knowledge of this field.
8

The Genetic Limits to Trait Evolution for a Suite of Sexually Selected Male Cuticular Hydrocarbons in Drosophila Serrata

Sztepanacz, Jacqueline L.P. January 2011 (has links)
Directional selection is prevalent in nature yet phenotypes tend to remain relatively constant, suggesting a limit to trait evolution. The genetic basis of evolutionary limits in unmanipulated populations, however, is generally not known. Given widespread pleiotropy, opposing selection on a focal trait may arise from the effects of the underlying alleles on other fitness components, generating net stabilizing selection on trait genetic variance and thus limiting evolution. Here, I look for the signature of stabilizing selection for a suite of cuticular hydrocarbons (CHCs) in Drosophila serrata. Despite strong directional sexual selection on CHCs, genetic variance differed between high and low fitness individuals and was greater among the low fitness males for seven of eight CHCs. Univariate tests of a difference in genetic variance were non-significant but have low power. My results implicate stabilizing selection, arising through pleiotropy, in generating a genetic limit to the evolution of CHCs in this species.
9

The Regulation of Worker Reproduction in the Ant Aphaenogaster cockerelli

January 2011 (has links)
abstract: The repression of reproductive competition and the enforcement of altruism are key components to the success of animal societies. Eusocial insects are defined by having a reproductive division of labor, in which reproduction is relegated to one or few individuals while the rest of the group members maintain the colony and help raise offspring. However, workers have retained the ability to reproduce in most insect societies. In the social Hymenoptera, due to haplodiploidy, workers can lay unfertilized male destined eggs without mating. Potential conflict between workers and queens can arise over male production, and policing behaviors performed by nestmate workers and queens are a means of repressing worker reproduction. This work describes the means and results of the regulation of worker reproduction in the ant species Aphaenogaster cockerelli. Through manipulative laboratory studies on mature colonies, the lack of egg policing and the presence of physical policing by both workers and queens of this species are described. Through chemical analysis and artificial chemical treatments, the role of cuticular hydrocarbons as indicators of fertility status and the informational basis of policing in this species is demonstrated. An additional queen-specific chemical signal in the Dufour's gland is discovered to be used to direct nestmate aggression towards reproductive competitors. Finally, the level of actual worker-derived males in field colonies is measured. Together, these studies demonstrate the effectiveness of policing behaviors on the suppression of worker reproduction in a social insect species, and provide an example of how punishment and the threat of punishment is a powerful force in maintaining cooperative societies. / Dissertation/Thesis / Ph.D. Biology 2011
10

Egg Policing and Fertility Signaling Across Colony Development in the Ant Camponotus floridanus

January 2012 (has links)
abstract: Of all the signals and cues that orchestrate the activities of a social insect colony, the reproductives' fertility pheromones are perhaps the most fundamental. These pheromones regulate reproductive division of labor, a defining characteristic of eusociality. Despite their critical role, reproductive fertility pheromones are not evenly expressed across the development of a social insect colony and may even be absent in the earliest colony stages. In the ant Camponotus floridanus, queens of incipient colonies do not produce the cuticular hydrocarbons that serve as fertility and egg-marking signals in this species. My dissertation investigates the consequences of the dramatic change in the quantity of these pheromones that occurs as the colony grows. C. floridanus workers from large, established colonies use egg surface hydrocarbons to discriminate among eggs. Eggs with surface hydrocarbons typical of eggs laid by established queens are nurtured, whereas eggs lacking these signals (i.e., eggs laid by workers and incipient queens) are destroyed. I characterized how workers from incipient colonies responded to eggs lacking queen fertility hydrocarbons. I found that established-queen-laid eggs, incipient-queen-laid eggs, and worker-laid eggs were not destroyed by workers at this colony stage. Destruction of worker-laid eggs is a form of policing, and theoretical models predict that policing should be strongest in incipient colonies. Since there was no evidence of policing by egg-eating in incipient C. floridanus colonies, I searched for evidence of another policing mechanism at this colony stage. Finding none, I discuss reasons why policing behavior may not be expressed in incipient colonies. I then considered the mechanism that accounts for the change in workers' response to eggs. By manipulating ants' egg experience and testing their egg-policing decisions, I found that ants use a combination of learned and innate criteria to discriminate between targets of care and destruction. Finally, I investigated how the increasing strength of queen-fertility hydrocarbons affects nestmate recognition, which also relies on cuticular hydrocarbons. I found that queens with strong fertility hydrocarbons can be transferred between established colonies without aggression, but they cannot be introduced into incipient colonies. Queens from incipient colonies cannot be transferred into incipient or established colonies. / Dissertation/Thesis / Ph.D. Biology 2012

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