On sex-ratio and sibling competition : an insight into reproductive decisions in the black-legged kittiwake (Rissa tridactyla)

Au cours d'un évènement de reproduction, les parents font face à plusieurs décisions qui peuvent influencer leur aptitude. Dans cette thèse, je me suis intéressé à la sexe-ratio et à la compétition dans la fratrie chez la mouette tridactyle (Rissa tridactyla). Tout d'abord, j'ai montré que les parents en moins bonne condition ont produit plus de filles que les autres, ce qui semblait dû à leur coût énergétique plus faible et peut-être aussi à leur plus grand retour en investissement en termes de valeur sélective pour les parents comparativement aux fils. Ensuite, mes résultats ont suggéré que l'asynchronie d'éclosion naturelle était celle qui minimisait les coûts pour les parents et pour les poussins cadets, alors que les poussins aînés semblaient être stressés par leur position dominante. Enfin, les mères ont favorisé la compétitivité de leur poussin cadet seulement lorsqu'elles étaient en conflit avec leur poussin aîné à propos de la réduction de taille de nichée. Cette thèse a donc mis en évidence certains moyens par lesquels les parents peuvent maximiser les bénéfices ou réduire les coûts associés à leur reproduction.During a breeding event, parents face several decisions that may impact their fitness. In this thesis, I have been interested in sex-ratio and sibling competition patterns in the black-legged kittiwake (Rissa tridactyla). First, I showed that parents in poorer condition overproduced daughters, which seems to be due to their lower reproductive cost and, possibly, to their higher fitness return for parents as compared to sons. Then, my results suggested that the natural magnitude of hatching asynchrony minimised the costs for parents and younger siblings, while older siblings seemed to be stressed by their dominant position. Finally, mothers favoured their younger chick's competitiveness only when in conflict over brood reduction with their older chick. This thesis thus highlighted some means through which parents could maximise benefits or reduce costs associated with their reproduction

Carry-over effects of food supplementation on recruitment and breeding performance of long-lived seabirds

Supplementation of food to wild animals is extensively applied as a conservation tool to increase local production of young. However, in long-lived migratory animals, the carry-over effects of food supplementation early in life on the subsequent recruitment of individuals into natal populations and their lifetime reproductive success are largely unknown. We examine how experimental food supplementation early in life affects: (i) recruitment as breeders of kittiwakes Rissa tridactyla born in a colony on Middleton Island (Alaska) between 1996 and 2006 (n = 1629) that bred in the same colony through 2013 (n = 235); and (ii) breeding success of individuals that have completed their life cycle at the colony (n = 56). Birds were raised in nests that were either supplemented with food (Fed) or unsupplemented (Unfed). Fledging success was higher in Fed compared with Unfed nests. After accounting for hatching rank, growth and oceanic conditions at fledging, Fed fledglings had a lower probability of recruiting as breeders in the Middleton colony than Unfed birds. The per-nest contribution of breeders was still significantly higher for Fed nests because of their higher productivity. Lifetime reproductive success of a subset of kittiwakes that thus far had completed their life cycle was not affected by the food supplementation during development. Our results cast light on the carry-over effects of early food conditions on the vital rates of long-lived animals and support food supplementation as an effective conservation strategy for long-lived seabirds

Age-related differences in the cloacal microbiota of a wild bird species

Background: Gastrointestinal bacteria play a central role in the health of animals. The bacteria that individuals acquire as they age may therefore have profound consequences for their future fitness. However, changes in microbial community structure with host age remain poorly understood. We characterised the cloacal bacteria assemblages of chicks and adults in a natural population of black-legged kittiwakes (Rissa tridactyla), using molecular methods. Results: We show that the kittiwake cloaca hosts a diverse assemblage of bacteria. A greater number of total bacterial OTUs (operational taxonomic units) were identified in chicks than adults, and chicks appeared to host a greater number of OTUs that were only isolated from single individuals. In contrast, the number of bacteria identified per individual was higher in adults than chicks, while older chicks hosted more OTUs than younger chicks. Finally, chicks and adults shared only seven OTUs, resulting in pronounced differences in microbial assemblages. This result is surprising given that adults regurgitate food to chicks and share the same nesting environment. Conclusions: Our findings suggest that chick gastrointestinal tracts are colonised by many transient species and that bacterial assemblages gradually transition to a more stable adult state. Phenotypic differences between chicks and adults may lead to these strong differences in bacterial communities. These data provide the framework for future studies targeting the causes and consequences of variation in bacterial assemblages in wild birds

Quality of Beverage Intake and Cardiometabolic and Kidney Outcomes: Insights From the STANISLAS Cohort

Background and Aims: Beverages are an important aspect of diet, and their quality can possibly affect health. The Healthy Beverage Index (HBI) has been developed to take into account these effects. This study aimed to highlight the relationships between health and beverage quality by assessing the association of the HBI and its components with kidney and cardiometabolic (CM) outcomes in an initially healthy population-based familial cohort. Methods: This study included 1,271 participants from the STANISLAS cohort. The HBI, which includes 10 components of habitual beverage consumption, was calculated. Associations of the HBI and its components with estimated glomerular filtration rate (eGFR), albuminuria, hypertriglyceridemic waist (HTG waist), metabolic syndrome (MetS), carotid-femoral pulse wave velocity (cfPWV), carotid intima-media thickness (cIMT), and left ventricular mass (LV mass) were analyzed using multivariable linear or logistic regression models. Results: The median HBI score was 89.7 (78.6–95) out of 100 points. While the overall HBI score was not significantly associated with any of the studied outcomes, individual HBI components were found differently associated with the outcomes. cfPWV and cIMT were lower in participants who did not meet the full-fat milk criteria (p = 0.03 and 0.001, respectively). In men, higher cfPWV was observed for the “low Fat milk” (p = 0.06) and “alcohol” (p = 0.03) non-adherence criteria. Odds of HTG waist were higher with the non-adherence to sugar-sweetened beverages criteria (p < 0.001). eGFR was marginally higher with non-adherence to the coffee/tea criteria (p = 0.047). Conclusions: In this initially healthy population, HBI components were differently associated with kidney and cardiometabolic outcomes, despite a good overall HBI score. Our results highlight specific impacts of different beverage types and suggest that beverages could have an impact on kidney and cardiometabolic health

Costs and benefits of sub-lethal Drosophila C Virus infection

Viruses are major evolutionary drivers of insect immune systems. Much of our knowledge of insect immune responses derives from experimental infections using the fruit fly Drosophila melanogaster. Most experiments, however, employ lethal pathogen doses through septic injury, frequently overwhelming host physiology. While this approach has revealed several immune mechanisms, it is less informative about the fitness costs hosts may experience during infection in the wild. Using both systemic and oral infection routes we find that even apparently benign, sub-lethal infections with the horizontally transmitted Drosophila C Virus (DCV) can cause significant physiological and behavioral morbidity that is relevant for host fitness. We describe DCV-induced effects on fly reproductive output, digestive health, and locomotor activity, and we find that viral morbidity varies according to the concentration of pathogen inoculum, host genetic background and sex. Notably, sub-lethal DCV infection resulted in a significant increase in fly reproduction, but this effect depended on host genotype. We discuss the relevance of sub-lethal morbidity for Drosophila ecology and evolution, and more broadly, we remark on the implications of deleterious and beneficial infections for the evolution of insect immunity

Pteridines and male quality in a dragon lizard

Data for the manuscript entitled "Seeing red: pteridines and male quality in a dragon lizard" published in the Biological Journal of the Linnean Societ

Seed mass and elevation explain variation in seed longevity of Australian alpine species

Conserving alpine ecosystems and the plant communities they contain using ex situ conservation requires an understanding of seed longevity. Knowledge of seed longevity may determine the effectiveness of ex situ seed banking for alpine plant conservation, and may provide insight into plant recruitment in situ. We sought to determine the influence of elevation and climatic variables, as well as plant and seed traits, on the seed longevity of 57 species inhabiting a unique biome, (sub-)alpine regions of mainland Australia. Seed longevity was estimated using controlled accelerated ageing tests to determine the time taken for seed viability to fall by 50%. We found that, across the study species, like alpine seeds elsewhere in the world, Australian alpine seeds are relatively short-lived and overall shorter-lived than Australian plants in general. Seed mass and elevation explained most of the variation in seed longevity among the Australian alpine species considered. Species with larger seed mass, and collections made at higher elevations, were found to have relatively short-lived seeds. Phylogeny, however, explained very little of the variation in longevity. Our results suggest that viability testing for Australian alpine seeds in ex situ seed banks should be conducted with shorter intervals than for the non-alpine flora. This study highlights how seed longevity in the Australian Alps is not dictated primarily by evolutionary lineage but rather by a complex combination of environmental variables and intrinsic seed characteristics. Potential implications for conservation ex situ and in situ in the context of climate change are discussed.A.S. was supported by an Australian Government Research Training Program (RTP) Scholarship. T.M. was supported by an Endeavour Research Fellowshi

Seeing red: pteridine-based colour and male quality in a dragon lizard

The animal kingdom is represented by a spectacular diversity of colourful species. However, for particular groups, such as lizards, we still know little about the nature of these colours and what they might signal about individual quality. In eastern water dragons (Intellagama lesueurii), males are larger than females and have a red venter. We first identified the pigments responsible for the red coloration. We then used visual modelling to determine how conspicuous red colouration is to a dragon lizard. Finally, we asked whether colour signalled male morphology and whether parasitized males had reduced coloration. The red coloration of male water dragons is produced by both carotenoid and pteridine classes of pigments, but predominantly by drosopterin, a coloured pteridine. Heavy males with large heads and in good body condition and those with fewer ticks had less intense red coloration on the chest, abdomen and thighs. However, size was not correlated with any colour variables. We explain the negative relationship between colour conspicuousness and morphological variables by the fact that less conspicuous males might have more melanin interspersed with red. Future studies are needed to investigate the interplay between pteridines and melanin in social signals of male quality in dragon lizards

Offspring sex-ratio and environmental conditions in a seabird with sex-specific rearing costs: a long-term experimental approach

International audienc

Cost of reproduction sex-ratio

Data and code for the paper on the cost of reproduction hypothesis and the analysis of the interaction between environmental conditions and parental investment capacity on offspring sex-rati