La coopération et les conflits sont les deux facettes de l’évolution sociale. L’objectif principal de cette thèse a été d’étudier chez les fourmis du complexe d’espèces Neoponera apicalis les mécanismes de régulation permettant de maintenir la coopération dans les groupes sociaux face aux risques d’exploitation internes et externes au groupe, à travers une approche comparative et intégrative. Nous montrons que la structure génétique des colonies entraine des conflits d’intérêts liés à la reproduction, notamment en ce qui concerne la production des mâles. L’étude de la régulation du partage de la reproduction révèle que les décisions reproductives des individus sont principalement basées sur la détection de signaux associés à la fertilité grâce à des capacités fines de discrimination de statut. Ces informations permettent aux ouvrières d’ajuster leur comportement reproducteur selon le contexte social et en fonction de leurs intérêts en termes d’inclusive fitness. En effet, alors qu’une auto-restriction reproductive des ouvrières est observée en présence d’une reine fertile, un conflit ouvert se déclare quand celle-ci disparait, régulé par la mise en place d’une hiérarchie reproductive linéaire dans laquelle les ouvrières de haut rang accèdent à la reproduction. Le signalement du statut reproducteur parait jouer un rôle capital dans la régulation des interactions de dominance/subordination, et donc dans la détermination des rangs hiérarchiques. Les signaux associés à la fertilité sont par ailleurs fortement conservés entre les différentes espèces de ce complexe, ce qui souligne leur honnêteté et donc leur stabilité évolutive. Nous montrons enfin l’existence d’une reconnaissance coloniale chez ces espèces, basée sur les mêmes indices de reconnaissance, et permettant de moduler la réponse territoriale selon le niveau de familiarité des colonies étrangères. Cette étude démontre donc l’importance des mécanismes de reconnaissance dans la régulation de la vie sociale. / ASocial evolution implies both cooperation and conflicts. The main objective of this thesis was to study the regulatory mechanisms allowing to maintain cooperation in social groups against exploitation from within and outside. We choose a comparative and integrative approach using ants of the Neoponera apicalis species complex. We show that the colony genetic structure gives rise to reproductive conflicts, particularly over male production. The study of the regulation of the partitioning of reproduction reveals that the individuals’ reproductive decisions are mainly based on the detection of fertility-associated signals through fine-scale status discrimination abilities. This information allows the workers to adjust their reproductive behaviour according to the social context and following their inclusive fitness interests. Whereas worker reproductive self-restraint is observed with a fertile queen, an overt conflict arises in queenless conditions, which is regulated through the formation of a linear reproductive hierarchy where high-ranking workers reproduce. Reproductive status signalling seems to play a crucial role in the regulation of the dominance/subordination relationships, and thus in the determination of hierarchical ranks. Furthermore, fertility-associated signals are highly conserved among the species of the complex, which highlights their honesty and thus their evolutionary stability. We finally show that the nestmate recognition processes in these species are based on the same recognition cues and allow to modulate the territorial response depending on the familiarity with non-nestmates. This study demonstrates the importance of recognition mechanisms in the regulation of social life.

Virtually all multicellular organisms are capable of developing differently in response to environmental variation. At the molecular level, such developmental plasticity requires interpretation and perpetuation of environmental signals without changing the underlying genotype. Such non-genetic, heritable information is known as epigenetic information. This dissertation examines epigenetic information among social insects, and how differences in such information relate to phenotypic caste differences. The studies included herein primarily focus on one form of epigenetic information: DNA methylation. In particular, these studies explore DNA methylation as it relates to and impacts (i) alternative phenotype and particular gene expression differences in two social insect species, (ii) histone modifications, another important form of epigenetic information, in insect genomes, and (iii) molecular evolutionary rate of underlying actively transcribed gene sequences. We find that DNA methylation exhibits marked epigenetic and evolutionary associations, and is associated with alternative phenotype in multiple insect species. Thus, DNA methylation is emerging as one important epigenetic mediator of phenotypic plasticity in social insects.

Este trabalho foi dividido em dois capítulos em formato de artigo científico, que fornecem informações sobre diversidade e ecologia de vespas sociais (Polistinae) em três áreas de floresta amazônica no estado de Rondônia. No primeiro capítulo comparamos índices de diversidade de áreas com diferentes níveis de interferência antrópica e apresentamos uma lista de espécies para a região. No segundo observamos a relação de alguns fatores ambientais abióticos (temperatura, umidade relativa do ar e intensidade luminosa) com o forrageio das vespas sociais durante a fotofase (06:00 18:00 h). Foram realizadas 42 coletas ativas com auxílio de solução atrativa (água, sal, açúcar), totalizando 504 horas de coleta de dados. Foram coletadas 2983 espécimes de vespas sociais, distribuídas em 76 espécies de Polistinae, sendo um dos trabalhos com maior diversidade de vespas sociais coletadas no Brasil. As vespas mais abundantes foram Agelaia Lepeletier e com maior riqueza de espécies Polybia Lepeletier. A área com maior interferência antrópica teve os índices de diversidade similares aos da área com menor interferência, com isto, concluímos que a diversidade de vespas sociais (Polistinae) não é um bom parâmetro para indicar o nível de preservação ambiental de fragmentos de floresta, uma vez que estes resultados já foram observados em áreas de Mata Atlântica. Quanto aos fatores abióticos, apenas a temperatura foi significante (P<0.05) e observamos que as atividades de forrageio de Polistinae ocorrem durante todo o período da fotofase, não priorizando horários específicos. / This study was divided into two chapters in format of scientific papers, which provide information about ecology and diversity of social wasps (Polistinae) in three areas of Amazon rainforest in state of Rondônia. In the first chapter we compare diversity indices of areas with different levels of human interference as well show a list of species for the region. In the second we present the relation between the abiotic environmental factors (temperature, relative humidity and light intensity) during the photophase (06:00 to 18:00 h) with the foraging of social wasps through statistical analysis. This study was conducted using active collection with an attractive solution (water, salt, sugar) in 42 collections, totaling 504 hours of data collection. We collected 2983 specimens of social wasps, distributed in 76 species of Polistine, being a survey with the greatest diversity of wasps collected in Brazil. The more abundant wasps were Agelaia Lepeletier and the greater richness was Polybia Lepeletier. Samples were taken in the area with the highest anthropogenic interference had diversity indexes near the area with less interference, it concluded with the diversity of social wasps (Polistine) is not a good parameter to indicate the level of environmental preservation of forest fragments, as well has been observed in surveys in the Atlantic forest. Regarding abiotic factors only temperature was significant (P<0.05), and we observed that the activities of Polistine occur throughout the entire photophase period do not prioritizing any specific times.

Este trabalho foi dividido em dois capítulos em formato de artigo científico, que fornecem informações sobre diversidade e ecologia de vespas sociais (Polistinae) em três áreas de floresta amazônica no estado de Rondônia. No primeiro capítulo comparamos índices de diversidade de áreas com diferentes níveis de interferência antrópica e apresentamos uma lista de espécies para a região. No segundo observamos a relação de alguns fatores ambientais abióticos (temperatura, umidade relativa do ar e intensidade luminosa) com o forrageio das vespas sociais durante a fotofase (06:00 18:00 h). Foram realizadas 42 coletas ativas com auxílio de solução atrativa (água, sal, açúcar), totalizando 504 horas de coleta de dados. Foram coletadas 2983 espécimes de vespas sociais, distribuídas em 76 espécies de Polistinae, sendo um dos trabalhos com maior diversidade de vespas sociais coletadas no Brasil. As vespas mais abundantes foram Agelaia Lepeletier e com maior riqueza de espécies Polybia Lepeletier. A área com maior interferência antrópica teve os índices de diversidade similares aos da área com menor interferência, com isto, concluímos que a diversidade de vespas sociais (Polistinae) não é um bom parâmetro para indicar o nível de preservação ambiental de fragmentos de floresta, uma vez que estes resultados já foram observados em áreas de Mata Atlântica. Quanto aos fatores abióticos, apenas a temperatura foi significante (P<0.05) e observamos que as atividades de forrageio de Polistinae ocorrem durante todo o período da fotofase, não priorizando horários específicos. / This study was divided into two chapters in format of scientific papers, which provide information about ecology and diversity of social wasps (Polistinae) in three areas of Amazon rainforest in state of Rondônia. In the first chapter we compare diversity indices of areas with different levels of human interference as well show a list of species for the region. In the second we present the relation between the abiotic environmental factors (temperature, relative humidity and light intensity) during the photophase (06:00 to 18:00 h) with the foraging of social wasps through statistical analysis. This study was conducted using active collection with an attractive solution (water, salt, sugar) in 42 collections, totaling 504 hours of data collection. We collected 2983 specimens of social wasps, distributed in 76 species of Polistine, being a survey with the greatest diversity of wasps collected in Brazil. The more abundant wasps were Agelaia Lepeletier and the greater richness was Polybia Lepeletier. Samples were taken in the area with the highest anthropogenic interference had diversity indexes near the area with less interference, it concluded with the diversity of social wasps (Polistine) is not a good parameter to indicate the level of environmental preservation of forest fragments, as well has been observed in surveys in the Atlantic forest. Regarding abiotic factors only temperature was significant (P<0.05), and we observed that the activities of Polistine occur throughout the entire photophase period do not prioritizing any specific times.

Relatively little is known about the temporal control of behavior of honey bee queens under natural conditions. To determine if mated honey bee queens possess diel rhythmicity in behavior, we observed them in glass-sided observation hives, employing two focal studies involving continuous observations of individual queens as well as a scan-sampling study of multiple queens. In all cases, all behaviors were observed at all times of the day and night. In four of the five queens examined in focal studies, there were no consistent occurrences of diel periodicity for any of the individual behaviors. A more encompassing measure for periodicity, in which the behaviors were characterized as active (walking, inspecting, egg-laying, begging for food, feeding, and grooming self) or inactive (standing), also failed to reveal consistent diel rhythmicity. Furthermore, there were no consistent diel differences in the number of workers in the queen's retinue. Behavioral arrhythmicity persisted across seasons and despite daily changes in both light and temperature levels. Both day and night levels of behavioral activity were correlated with daytime, but not with nighttime, ambient temperatures. The behavior of the one exceptional queen was not consistent: diurnal activity patterns were present during two 24-h observation sessions but arrhythmicity during another. Based on the behavior observed by all but one of the queens examined in this work, the arrhythmic behavior by the mated honey bee queen inside the colony appears to be similar to that exhibited by worker bees before they approach the age of onset of foraging behavior.

Body size is a universal property affecting biological structure and function, from cell metabolism to animal behavior. The nervous system, the physical generator of behavior, is also affected by variations in body size; hence potentially affecting the way animals perceive, interpret and react to the environment. When animals join to form groups, such individual differences become part of the structure of the society, even determining social roles. Here, I explore the association between body size, behavior and social organization in honeybees and bumblebees. Focusing on bumblebees, I explore the link between body size, brain allometry and learning and memory performance, within the context of task specialization. I show that body size goes along with brain size and with learning and memory performance, and that foraging experience affects such cognitive and neural features. Next, I explore the association between body size and foraging task specialization in honeybees. Previous evidence showed a link between specialization on pollen or nectar foraging and sensory sensitivity, further associating sensitivity to the quality and/or quantity of resource exploited. I hypothesize that, as in solitary bees, larger body size is associated with higher sensory sensitivity. I test this hypothesis by comparing body size and the quality and quantity of the resource exploited by wild Africanized and European honeybees. I show that nectar foragers are smaller and have fewer olfactory sensilla, which might underlie their lower sensitivity to odors. Also, larger bees collect more pollen (within pollen foragers) and more dilute nectar (within nectar foragers). To further test this `size hypothesis', I compare strains of bees selected to store large ("high strain") or small ("low strain") amounts of pollen surplus. As these strains differ in sensory sensitivity, I predict that the more sensitive high strain bees are larger and have more sensory sensilla. I show that high strain bees are generally bigger, but have fewer sensory sensilla than low strain bees. These results show that in bees, body size is associated with an individual's sensory, neural and cognitive features, further suggesting that body size plays a more important role in the organization of bee societies than generally assumed.

Polymorphism is the existence of multiple phenotypes within a given species in a population. In social insects, worker polymorphism plays a key role in maximizing the effectiveness of the division of labor. Some ants have an extreme form of worker polymorphism where workers have a broad size range and multiple size modes. Pheidole ants, for example, consist of both highly polymorphic species as well as those with relatively low polymorphism. Here, we examined why different Pheidole species have different degrees of polymorphism and how polymorphism is produced. We thoroughly characterized the worker caste systems of P. spadonia, P. rhea, P. obtusospinosa, and P. tepicana. There were significant differences among the four species in size range, number of size modes, caste ratios, allometry, and caste biomass allocation. An examination of worker caste traits of P. spadonia, P. rhea, and P. obtusospinosa revealed that as head size increased for all three species: (1) mandibles became broader and less serrated, (2) head muscle volume increased, and (3) bite force increased. These traits of large supersoldiers are likely adapted for crushing while those of small minors are likely for cutting. Foraging experiments showed that P. spadonia, P. rhea, and P. obtusospinosa used their workforce in different ways for food processing outside the nest. For P. rhea, the frequency of supersoldiers involved in food processing increased as the processing level required increased. However, P. obtusospinosa supersoldiers were rarely found processing food outside the nest and P. spadonia soldiers assisted in processing dead prey but did not help at all in processing live prey. P. obtusospinosa and P. spadonia workers may be more involved with other colony tasks. This hypothesis was confirmed when field observations of P. obtusospinosa showed supersoldiers participating in head-blocking at their entrance to fend off invading army ants; no other castes exhibited this behavior. Lastly, we tested genetic influences on worker polymorphism. We found that as colony genetic diversity increased (via polyandry), the degree of polymorphism increased. We also showed evidence of paternal genes influences on the development of worker castes in the highly polymorphic P. rhea.

A colony of social insects has many tasks to complete for the good of the colony. The tasks, such as brood care, feeding, foraging and building, could be split among its members (implying specialization). Alternatively, ants could just freely switch between tasks, either doing whatever needs to be done or whatever tasks they come into contact with. If individuals switch from one task to another, they may incur costs, including a time cost. So far, research has yet to quantify such task switching costs. To learn more about switching cost, specifically quantifying the cost in terms of time, videos of Temnothorax rugatulus were observed for specific tasks, such as brood care, feeding, foraging and building. The switching costs were measured in two ways depending on whether the non-switching time or switching time were being measured. For the non-switching time between bouts of the same task, the interval time started when the ant stopped touching the brood item and ended when the ant started touching the brood item. For the switching time between two different tasks, time began when the ant stopped one task and ended when the ant began a second task. The interval time was calculated by recording the time, using the timeline on the video, that the ant stopped one task (or bout of one task) and moved on the next. The data collected from the videos were analyzed using a Welch Two-Sample T-test. Through the study, it was discovered that there was, in fact, no significant delay when Temnothorax rugatulus switch from one task to another.

Social Hymenoptera (wasps, ants, bees) possess a unique mode of reproduction. Typically, males produce the total amount of their spermatozoa during the nymphal phase solely from the energy reserves acquired during the larval phase. When the adult male hatches, the testes regress and the spermatozoa are then stored in their seminal vesicles. Mating takes place during a mating flight in which hundreds of males and females from surrounding colonies participate only once in their life. Sperm cells are transmitted during mating and are stored in the queen's spermatheca for the rest of its life (which can last several decades depending on the species). After mating, the male dies and the queen founds a new colony from the sperm received during the nuptial flight. She will never re-mate again and will use parsimoniously the spermatozoa to fertilize her eggs. Several factors are likely to dammage sperm cells, among them nutritional deficiencies during development, pathogens transmitted during mating or the immune defenses of the female that hosts sperm. Yet these sperm cells are extremly valuable because they are not renewable, and the queen will use them throughout her whole life to maintain a sufficient working force ensuring all the functions of the colony. The reproductive success of both males and females is highly dependent on the protection and maintain of spermatozoa.In this work we studied different factors that can affect the quantity, quality and protection of sperm in ants. The focus was made at three different stages: during the production of sperm cells, during their transmission at the time of mating and during their storage in the queen’s spermatheca. First, we showed that the investment in somatic development and in sperm quality take precedence over the production of large quantities of sperm cells. Second, we tested the presence and activity of two major components of the immune system (phenoloxidase system and antibacterial substances) in the sexual organs of virgin and mated ants, and we show that sperm protection uses specific systems which response is variable over time. In addition, we studed the temporal variations of these immune responses in the general insect system before and after mating. Finally, we examine the bacterial abundances and communities present in the reproductive organs at these same periods. We show the presence of some bacterial groups from the sperm storage organs that could play a role in the maintenance of spermatozoa. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The distribution of resources is vital to any system or society. This is particularly true of social insect colonies where independent access to resources is not available to all members. Only a fraction of individuals are responsible for obtaining food for the colony from outside the nest. Surprisingly little is known about how this food is subsequently distributed to members inside the nest. The work in this thesis is focused around a set of food distribution experiments conducted using four colonies of the ant Temnothorax albipennis. The study applies a well-used technique in a new way to investigate the distribution of food under two different scenarios: feeding under normal conditions and famine relief feeding after a period of starvation. All ants in each colony are marked and then individually tracked recording every feeding interaction to obtain a complete network of food transmission. This work has shown that all four colonies efficiently relieved the famine within 30 minutes of introducing new food. This process was facilitated by workers abandoning their spatial structure and expanding their space use; feeding multiple recipients from a single donor; and simultaneously spreading stored food and new food. Recruitment of foragers did not play a major role in relieving the famine but foragers were responsible for most of the first round of feeding. The study revealed that not all members received the same amount of food and most ants received food in multiple feeding interactions. The transmission pathways used to distribute the food present an opportunity for harmful substances to spread. The pathways are explored in this context to see whether the colonies might aim to minimize the spread by partitioning the pathways or maximise spread by mixing to promote social immunity. The study reveals behavioural differences between the four colonies which are likely to result from the inherent variation in demographic and geometric properties. These differences highlight the flexibility of ant colonies during problem solving under different conditions.