Biology subjects

Debias, F.

Publications and source records attributed to Debias, F..

3 recordsLinked to original sources

bioRxiv2023

Foraging at night under artificial light: consequences on reproductive senescence and lifetime reproductive success for a diurnal insect

O_LIThe increasing use of artificial light at night (ALAN) is currently a major anthropogenic disturbance, with largely unappreciated eco-evolutionary consequences for nocturnal but also diurnal organisms. It has been hypothesized that light pollution could create new opportunities for the latter to forage and reproduce at night, which is called the night-light niche, with fitness consequences still scarcely explored. C_LIO_LIWe exposed diurnal parasitoid wasps (Venturia canescens) to one of three light-at-night conditions: control (0 lux), low intensity (0.7 lux) or high intensity (20 lux) throughout their lives. We then monitored changes in both behavioural and life-history traits, namely daytime and nighttime feeding and egg-laying activity, reproductive senescence, lifespan and lifetime reproductive success. C_LIO_LILight pollution influenced the nighttime activity of wasps. The proportion of wasps feeding and laying eggs at night increased, and we also detected a tendency for a higher nighttime reproductive success under a high intensity of light pollution. Surprisingly, high intensity of light pollution also increased the wasps lifespan. Such changes did not affect the lifetime reproductive success of the wasps, but influenced the distribution of ovipositions between day and night. C_LIO_LIReproductive senescence occurs in V. canescens, evidenced by the linear decline in daily reproductive success with age regardless of the light condition. ALAN conditions, in interaction with mother age, affected developmental time in offspring, highlighting an effect on reproductive senescence. C_LIO_LIWe demonstrated that light pollution induced the use of the night-light niche in a diurnal insect, with a shift in the distribution of egg-laying events between day and night. While we did not observe strong consequences on individual fitness, such changes in the dynamics of parasitism behaviour may nevertheless have major consequences for population dynamics, especially in natural conditions. C_LI

animal behavior and cognition↗

bioRxiv2022

The environmental roots of the relationship between glucocorticoids and body mass in the wild

Environmental fluctuations force animals to adjust glucocorticoids (GCs) secretion and release to current conditions. GCs are a widely used proxy of an individual stress level. While short-term elevation in GCs is arguably beneficial for fitness components, previous studies have documented that the relationship between long-term baseline GCs elevation and fitness components can vary according to ecological and individual factors and according to the life-history of the species studied. Using longitudinal data on roe deer (Capreolus capreolus) from two populations facing markedly different environmental contexts, we tested whether baseline GC levels negatively correlate with body mass - a trait positively associated with demographic individual performance - on the short- to long-term. In support, higher baseline GC concentrations were associated to lighter body mass, both measured during the same capture event, in adults of both populations. Overall, we showed that despite the marked environmental and demographic differences between populations and despite the between-sex differences in life history (i.e. reproductive tactics), the relationship between body mass and GCs is consistent across environmental contexts, but might differ according to the life history stage of an individual. This work opens promising perspectives to further explore the relationship between GC and fitness-related traits according to life history stages in free-ranging mammals across seasonal and environmental contexts. The timing and context-dependence of GC levels highlight the complexity of studying stress responses in the wild.

ecology↗

bioRxiv2022

Age and spatio-temporal variations in food resources modulate stress-immunity relationships in three populations of wild roe deer

Living in variable and unpredictable environments, organisms face recurrent stressful situations. The endocrine stress response, which includes the secretion of glucocorticoids, helps organisms to cope with these perturbations. Although short-term elevations of glucocorticoid levels are often associated with immediate beneficial consequences for individuals, long-term glucocorticoid elevation can compromise key physiological functions such as immunity. While laboratory works highlighted the immunosuppressive effect of long-term elevated glucocorticoids, it remains largely unknown, especially in wild animals, whether this relationship is modulated by individual and environmental characteristics. In this study, we explored the co-variation between baseline cortisol levels, assessed non-invasively using faecal cortisol metabolites (FCMs), and 12 constitutive indices of innate, inflammatory, and adaptive immune functions, in wild roe deer living in three populations with contrasting environmental conditions. Using longitudinal data on 564 individuals, we further investigated whether age and spatio-temporal variations in the quantity and quality of food resources affect the relationship between FCMs and immunity. Negative covariation with glucocorticoids was evident only for innate and inflammatory markers of immunity, while adaptive immunity appeared to be positively or not linked to glucocorticoids. In addition, the negative covariations were generally exacerbated, or revealed, in individuals facing harsh environmental constraints and in old individuals. Therefore, our results highlight the importance of measuring multiple immune markers of immunity in individuals from contrasted environments to unravel the complex relationships between glucocorticoids and immunity in wild animals. Our results also help explain conflicting results found in the literature and could improve our understanding of the long-term consequences of elevated glucocorticoid levels on disease spread and population dynamics.

ecology↗