Social Dynamics in Paper Wasps: The case of nest-drifting in Polistes canadensis

Le passage de la vie solitaire à la vie sociale représente une des principales transitions évolutives. La socialité a évolué au sein de plusieurs taxons du règne animal et notamment chez les insectes sociaux qui ont atteint son niveau le plus élevé : l'eusocialité. Les colonies d'insectes sociaux se composent d'une reine, qui monopolise la reproduction, et d'ouvrières, non-reproductrices ou parfois stériles, qui aident à élever la descendance de la reine. Selon la théorie de la sélection de parentèle, les ouvrières augmentent leur fitness (succès reproducteur) non pas à travers leur propre progéniture, mais en aidant des individus apparentés (leur reine) à produire davantage de descendants. Cette théorie prédit ainsi que les ouvrières ont un intérêt à rester fidèles à leur nid natal. Toutefois, chez la guêpe tropicale Polistes canadensis, de nombreuse ouvrières visitent d'autres nids que leur nid natal : un phénomène appelé « dérive des ouvrières ». Le but de ce doctorat est ainsi de mieux comprendre les mécanismes impliqués dans ce comportement particulier des ouvrières ainsi que ces implications pour la théorie de la sélection de parentèle. Nous avons examiné le comportement de dérive des ouvrières à travers une étude des dynamiques sociales chez la guêpe tropicale P. canadensis. Mes résultats montrent que les populations de P. canadensis se composent en différentes agrégations de nids. Malgré de précédentes suggestions, on n'observe qu'une faible viscosité génétique au sein des populations de P. canadensis étudiées. On retrouve toutefois un degré d'apparentement entre nids d'une même agrégation. Ceci suggère que les ouvrières dériveuses sont susceptibles de bénéficier de fitness indirect en aidant les nids proches géographiquement. De plus, ces échanges d'ouvrières ne semblent pas accidentels puisque l'on constate des variations de taux de dérive et puisque les déplacements observés entre nids persistent sur plusieurs périodes de temps. La charge de travail, qui correspond aux différences d'effort de fourragement entre nid visités et natals, est décrite dans notre étude comme potentiel facteur expliquant le comportement de dérive des ouvrières chez P. canadensis. Nos expériences de retrait d'ouvrières et de couvain ont révélées que les dériveuses ne semblent pas répondre aux changements de besoins en aide des nids visités. Les ouvrières dériveuses biaisent leur effort en aidant leur propre nid, par lequel elles bénéficient le plus en termes de fitness indirect, avant de se consacrer à tout autre nid. Dans l'ensemble, ces résultats sur la dérive des ouvrières chez P. canadensis sont cohérents et suggèrent que ce comportement est une importante stratégie de reproduction alternative chez cette espèce qui contribue à la fitness indirecte de ces ouvrières non-reproductrices. De plus, ce doctorat apporte des informations sur la structure génétique des populations de guêpes Polistes et décrit le rôle des ouvrières inactives. Celles-ci semblent servir de réserve en ouvrières apportant du support à la colonie dans l'éventualité d'une perte d'individus. Plus généralement, ce travail met l'accent sur l'organisation complexe et l'adaptabilité des individus dans les sociétés d'insectes. - One major transition in evolution is the shift from solitary to social life. Sociality has evolved in a few taxa of the animal kingdom, most notably in the social insects which have achieved the highest level of sociality: eusociality. Colonies of social insects are formed by a reproductive queen, and many non-reproductive or sterile workers who help raise their mother queen's offspring. Kin selection theory explains worker behaviour in terms of the indirect fitness they gain from raising non-offspring kin. It therefore predicts that workers should stay faithful to their natal nests, to which they are the more related. However, in the tropical paper wasps Polistes canadensis, high levels of nest-drifting, whereby workers spend time on other neighbouring nests, has been reported. This PhD aimed at understanding the mechanisms involved in this peculiar behaviour as well as its implications for kin selection theory. I examined nest-drifting through the study of the social dynamics of the tropical paper wasp P. canadensis. My results showed that populations of this species of paper wasps are composed of different aggregations of nests. The studied populations showed little limited dispersal (viscosity), despite previous suggestion, but nests within these aggregations were more related to each other than nests outside of aggregations. This suggested that drifters may benefit from indirect fitness when helping on neighbouring nests. Drifting was unlikely to be accidental since we found drifting patterns at various rates and consistently over several time periods during monitoring. Workload (differences in colony-level foraging effort) was also a potential factor explaining nest-drifting in P. canadensis. Worker and brood removal experiments revealed that drifters do not respond to any changes in the need for help in the non-natal nests they visit. Drifters thus bias their help in their natal nests, from which they may benefit the most in terms of indirect fitness, before investing in others. Altogether, these results on nest-drifting in P. canadensis are consistent and suggest that nest-drifting is an important alternative reproductive strategy, contributing to the indirect fitness benefits gained by non-reproductive wasps. Additionally, this PhD provides information on the genetic structure of paper wasps' populations and demonstrates the role of inactive or lazy wasps as a "reserve worker force", which provides resilience to the colony in the event of worker mortality. More generally, this work further highlights the complex organization and adaptability of individuals in insect societies.

Douteurs thoraciques en médecine ambulatoire. Sans oublier les patients qui n'ont "rien au coeur" [Thoracic pain in primary care. Don't forget the patients without heart disease].

Thoracic pain in primary care. Don't forget the patients without heart disease Thoracic pain is a frequent medical complaint. Diagnostic and therapeutic guidelines have been developed and evaluated mostly in emergency and hospital settings. The primary care practitioner, as the emergency room doctor, has to identify quickly any severe condition needing urgent and highly specialized treatment. But in primary care, the process is not finished then! A patient with no vital and urgent problem still needs a diagnosis, information and adequate treatment. This review goes over the presentation of thoracic pain, the differential diagnoses and the challenge of treating such patients in ambulatory care.

Traités de médecine.

Parmi lesquels : Liber dinamidiorum Galieni quem fecit Mecenati simplicium medicaminum (12) ; liber passionarius (139).

Urban health: l'irrémédiable urbanisation de la vie et de la médecine [Urban health: the irremediable urbanization of life and medicine].

Since 2007, the number of people living in cities exceeds that of rural areas. Thus, cities and their organizations have a major influence on all spheres of human life, especially health. This influence may generate inequality, suffering and disease, but also represent an opportunity for health and well-being. This paper introduces the concept of urban health, particularly in terms of primary care medicine and presents solutions that encompass a wide field (politics, urban planning, social inequality, education). Improving urban health requires collaboration of medical with non-medical actors, in order to become of development (re-) urban structure and promotes the health of all.

Médecine de l'adolescence. La Guglera: une réponse nouvelle et originale aux adolescents gravement obèses et sans travail [Adolescent medicine in Guglera: a novel approach for unemployed, severely obese adolescents]

The Center "la Guglera", located in the canton of Fribourg (Switzerland) provides a novel approach to the care of severely obese adolescents who are currently unemployed. These young people, whose BMI is usually higher than 35 to 40 kg/m2 spend a 6 to 12 months long stay in an in-patient institution which also takes care of other unemployed non obese adolescents on an outpatient basis. Besides a nutritional education which is part of the everyday life of the institution, the program includes a generous amount of hours of physical activities and sports. The adolescents also participate in a rehabilitation training program which fosters the future integration in a professional milieu, such as an apprenticeship. The short term results of la Guglera seem very promising. The program is financially co-supported by the Swiss and cantonal administrations, the insurance companies and the parents.

Le compas & le bistouri. Architecture de la médecine et du tourisme curatif : l'exemple vaudois (1760-1940)

Les établissements médicaux vaudois construits entre 1760 et 1940 sont des témoins privilégiés de l'émergence de l'architecture rationnelle ainsi que de phénomènes historiques et sociaux tels que la médicalisation de la société et du territoire, l'essor du tourisme médical, le transfert des modèles et des technologies. L'étude des hôpitaux, des sanatoriums, des cliniques et des établissements de bains montre comment l'invention d'une « architecture à soigner » est le fait conjoint du médecin et de l'architecte, tous deux cherchant à faire de ces établissements des faire-valoir de leur pratique ainsi que des monuments à la gloire de la santé publique ou de la philanthropie.

Complexité, médecine générale et réformes des systèmes de santé [Complexity, general practice and reforms of health systems].

The family doctor facing complexity must decide in situations of low certainty and low agreement. Complexity is in part subjective but can also be measured. Changes in the health systems aim to reduce health costs. They tend to give priority to simple situations and to neglect complexity. One role of an academic institute of family medicine is to present and promote the results of scientific research supporting the principles of family medicine, taking into account both the local context and health systems reforms. In Switzerland the new challenge is the introduction of managed care.