Biology subjects

Lemaitre, J.-F.

Publications and source records attributed to Lemaitre, J.-F..

18 recordsLinked to original sources

bioRxiv2025

A MammaLian Demographic Database for comparative analyses of evolutionary biodemography: malddaba

The question of how individual age influences demographic transition rates, such as survival probabilities and reproduction rates, has long been a main question for demographers and evolutionary ecologists. This has resulted in the accumulation of studies estimating the age-specific demographic transition rates across the tree of life over the last few decades. Although this accumulation of studies has enabled comparative demographic analyses to be developed, such analyses remain difficult to perform because age-specific data are scattered across literature. Here, we present a new open-access database, malddaba, which compiles age-specific demographic rates for mammals in the wild from published information. Currently, the database encompasses 170 species from 250 publications, representing 428 age- and sex-specific survival series and 199 age- and sex-specific reproduction series. Each series is reported using a standardized approach aimed at facilitating the extraction and use of that dataset by anyone interested in comparative biology. We show how malddaba can be used to address a variety of questions, ranging from comparative ageing with the assessment of actuarial and reproductive senescence patterns in a wide diversity of mammals. We can also address questions related to comparative population dynamics. For this purpose, in addition to the raw demographic rate records, we were able to build 43 population-specific life tables using malddaba records, which allow demographic outputs to be estimated accurately, such as population growth rate and generation time for those species. The malddaba database will be regularly updated to keep adding new demographic estimates and bring a comprehensive and dynamic view of the diversity of demographic trajectories across mammals.

ecology↗

bioRxiv2025

No baby boom of social mammals in European zoos resulting from COVID-19 lockdowns

Most zoo animals are exposed daily to human visitors, which could be a major disturbance on reproduction. Although few studies have examined the relationship between number of births and crowd size by comparing high and low visitor days, the effect of zoo visitors on animal reproduction over longer timescales has been overlooked. We assessed whether number of births in 34 social mammal species hosted in zoos from 23 European countries differed after prolonged periods of closure to the public (COVID-19 lockdowns) as compared with preceding years. An analysis restricted to the periods following the lockdowns and corresponding to any conception during closure (from 2020 to 2022), compared with the same periods in the two previous years (2018 and 2019), showed no effect of zoo closure on number of births, even when considering each species life history traits and whether they were managed under a breeding programme. We found no evidence that a complete and prolonged absence of visitors affected the ability to reproduce in social mammals housed across European zoos. By analysing birth variation in a large sample of mammalian species, this study contributes to a better knowledge of the natality of mammals in captive settings opened to the public.

zoology↗

bioRxiv2025

Likely circulation of a coronavirus in roe deer (Capreolus capreolus) populations suggested by SARS-CoV-2 serological investigation in France

The risk of viral transmissions from domestic/wild animals to humans is a major public health concern. Humans can also transmit viruses back to domestic and wild animals, acting as reservoir for virus maintenance and sources of epidemic diseases re-emergence. The SARS-CoV-2, causing COVID-19, likely originated from wildlife and has been evidenced to transmit from humans to captive, domestic and wild animals. White-tailed deer (Odocoileus virginianus) show high SARS-CoV-2 prevalence following human contamination, suggesting they could act as an emerging virus reservoir. We completed recent research on European cervid species by investigating whether SARS-CoV-2 had emerged in longitudinally-monitored European roe deer (Capreolus capreolus) populations in direct contact with humans in France. We performed indirect tests (serological ELISAs and seroneutralization) on sera collected before and after the virus emergence in humans, and direct RT-PCR tests on nasal swabs collected in 2022. We also investigated the virus exposure and prevalence in three other cervid species. ELISA tests were positive for 2.20% of sera, pre- and post-pandemic, but seroneutralization and PCR tests were negative. Although one population showed increased seroprevalence post-2020, results suggest that SARS-CoV-2 has not emerged in those populations, and that ELISA cross-reaction with one or several unidentified circulating coronaviruses is possible.

immunology↗

bioRxiv2025

Exploring the role of transposable elements to sex gap in longevity in Drosophila species

In Drosophila, like in many other animal species, females tend to live longer than males, a phenomenon known as sex gap in longevity (SGL). One possible explanation for this phenomenon could be related to the activity of transposable elements (TE), which may be present at higher levels in the heterogametic sex. TE activity is normally repressed by epigenetic mechanisms, but this regulation weakens with age. Sex chromosomes, such as the Y chromosome, are enriched in TEs, and age-related TE activity may therefore be more pronounced in older males than in older females, likely affecting longevity patterns. Using three Drosophila species, we show that SGL varies naturally among wild-type populations, reflecting both intra-and inter-species differences. Transcriptomic data revealed increased age-related TE expression in D. melanogaster and D. suzukii flies, but not in D. simulans. Moreover, we observed a higher number of upregulated TE copies in older males compared to older females across all the three species tested. Additionally, we detected an increase in TE-chimeric transcript generation in some aged samples, particularly in D. suzukii males. Finally, the replacement of the Y chromosome between strains with different SGL led to a progressive reduction in male lifespan and increased TE transcriptional release over generations, suggesting a Y chromosome important role in male longevity. Our work highlights the importance of investigating the role of TEs to better understand differences in longevity between sexes and across different species.

genomics↗

bioRxiv2024

Demographic pathways linking sex-chromosome system to adult sex ratio variation across tetrapods

Sex chromosomes determine male and female phenotypes, and the resulting sex differences can have significant impacts on ecology and life history. One manifestation of this link is that ZZ/ZW sex-determination systems are associated with more male-skewed adult sex ratio (ASR, proportion of males in the adult population) than XY/XX systems across tetrapods (amphibians, reptiles, birds, and mammals). Here we investigate four demographic processes: male and female offspring production, sex differences in juvenile and adult mortalities and in timing of maturation that can contribute to ASR variation between XY/XX and ZZ/ZW systems, using phylogenetic analyses of a large dataset collected from tetrapod species in the wild. We show that sex differences in adult mortality reliably predict ASR, and it is also more male-biased in XY/XX species than in ZZ/ZW species. Sex differences in juvenile mortality or in maturation time also contribute to ASR skews, but do not differ consistently between XY/XX and ZZ/ZW systems. Phylogenetic path analyses confirm an influence of sex-determination system on ASR through sex-biased adult mortality. Thus, these results infer that sex chromosomes can impact, via demographic pathways, frequency-dependent selection emerging from the relative number of males and females. We call for follow-up studies to uncover the potentially complex web of associations between sex determination, population dynamics, and social behaviour.

evolutionary biology↗

bioRxiv2024

Early-life glucocorticoids accelerate lymphocyte count senescence in roe deer

Immunosenescence corresponds to the progressive decline of immune functions with increasing age. Although it is critical to understand what modulates such a decline, the ecological and physiological drivers of immunosenescence remain poorly understood in the wild. Among them, the level of glucocorticoids (GCs) during early life are good candidates to modulate immunosenescence patterns because these hormones can have long-term consequences on individual physiology. Indeed, GCs act as regulators of energy allocation to ensure allostasis, are part of the stress response triggered by unpredictable events and have immunosuppressive effects when chronically elevated. We used longitudinal data collected over two decades in two populations of roe deer (Capreolus capreolus) to test whether higher baseline GC levels measured within the first year of life were associated with a more pronounced immunosenescence and parasite susceptibility. We first assessed immunosenescence trajectories in these populations facing contrasting environmental conditions. Then, we found that juvenile GC levels can modulate lymphocyte trajectory. Lymphocyte depletion was accelerated late in life when FGMs were elevated early in life. Although the exact mechanism remains to be elucidated it could involve a role of GCs on thymic characteristics. In addition, elevated GC levels in juveniles were associated with a higher abundance of lung parasites during adulthood for individuals born during bad years, suggesting short-term negative effects of GCs on juvenile immunity, having in turn long-lasting consequences on adult parasite load, depending on juvenile environmental conditions. These findings offer promising research directions in assessing the carry-over consequences of GCs on life-history traits in the wild.

physiology↗

bioRxiv2023

Transposable element expression with variation in gonosome number supports a toxic Y effect on human longevity

AO_SCPLOWBSTRACTC_SCPLOWWhy women live longer than men is still an open question in human biology. Sex chromosomes have been proposed to play a role in the observed sex gap in longevity, and the Y male chromosome has been suspected of having a potential toxic genomic impact on male longevity. It has been hypothesized that in aging individuals, TE repression is diminished, which could lead to detrimental effects (e.g. somatic mutations, perturbed gene expression) and to an acceleration of the aging process. As the Y chromosome is typically enriched in transposable elements (TE), this could explain why the presence of a Y chromosome is associated with shorter longevity. Using transcriptomic data from humans with atypical karyotypes, we found an association between TE expression and the presence and number of Y chromosomes. These findings are consistent with the existence of a toxic Y effect on men's longevity.

molecular biology↗

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

Deleterious effects of thermal and water stresses on life history and physiology: a case study on woodlouse

We tested independently the influences of increasing temperature and decreasing moisture on life history and physiological traits in the arthropod Armadillidium vulgare. Both increasing temperature and decreasing moisture led reproductive success to decrease. While the density of immune cells decreased and the {beta}-galactosidase activity increased with increasing temperature and decreasing moisture, which suggests a negative impact of these stressors on individual performance, increased temperature and decreased moisture affected differently the other biomarkers conjuring different underlying mechanisms depending on the stress applied. Our findings demonstrate overall a negative impact of high temperature and low moisture on woodlouse welfare. Changing temperature or moisture had slightly different effects, illustrating the need to test further the respective role of each of these key components of climate change on organisms to predict more reliably the future of our ecosystems.

evolutionary biology↗

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

Body mass change over winter is consistently sex-specific across roe deer populations

In most polygynous vertebrates, males must allocate energy to growing secondary sexual characteristics, such as ornaments or weapons, that they require to attract and defend potential mates, impacting body condition and potentially entailing fitness costs. We investigated sex differences in over winter body mass change across five intensively monitored populations of roe deer (Capreolus capreolus) with markedly contrasting environmental conditions. At winter onset, males weighed, on average, 8.4% (from 4.7% in the most northerly population to 11.6% in the most southerly one) more than females. However, across all populations, males fared worse over the winter than females, losing more (Sweden) or gaining less (France) mass, so that sexual mass dimorphism was virtually absent prior to the onset of spring. Our findings reveal that the direction of over-winter change in mass of roe deer depends on winter severity, but that males are consistently more sensitive to this environmental constraint than females. As a result of this sex-specific change in body mass, sexual mass dimorphism is lowest at the onset of the territorial season. We suggest that allocation to antler growth and territory establishment drives this pattern, providing a likely explanation to account for the lower rates of male adult survival that are consistently reported in this weakly dimorphic species.

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↗

bioRxiv2021

Sex chromosomes, sex ratios and sex gaps in longevity in plants

In animals, males and females can display markedly different longevity (also called sex gap in longevity, SGLs). Recent work has revealed that sex chromosomes contribute to establishing these SGLs. X-hemizygosity and toxicity of the Y chromosomes are two mechanisms that have been suggested to reduce male longevity (Z-hemizygosity and W toxicity in females in ZW systems). In plants, SGLs are known to exist but the role of sex chromosomes remains to be established. Here, by using adult sex ratio as a proxy for measuring SGLs, we explored the relationship between sex chromosome and SGLs across 43 plant species. Based on the knowledge recently accumulated in animals, we specifically asked whether: (i) species with XY systems tend to have female-biased sex ratios (reduced male longevity) and species with ZW ones tend to have male-biased sex ratios (reduced female longevity), and (ii) this patterns was stronger in heteromorphic systems compared to homomorphic ones. Our results tend to support these predictions although we lack statistical power because of a small number of ZW systems and the absence of any heteromorphic ZW system in the dataset. We discuss the implications of these findings, which we hope will stimulate further research on sex-differences in lifespan and ageing across plants.

plant biology↗

bioRxiv2020

Is degree of sociality associated with reproductive senescence? A comparative analysis across birds and mammals

Our understanding on how widespread reproductive senescence is in the w ild and how the onset and rate of reproductive senescence vary among species in relation to life histories and lifestyles is currently limited. More specifically, whether the species-specific degree of sociality is linked to the occurrence, onset and rate of reproductive senescence remains unknown. Here, we investigate these questions using phylogenetic comparative analyses across 36 bird and 101 mammal species encompassing a wide array of life histories, lifestyles and social traits. We found that female reproductive senescence (1) is widespread and occurs with similar frequency (about two thirds) in birds and mammals; (2) occurs later in life and is slower in birds than in similar-sized mammals; (3) occurs later in life and is lower with an increasingly slower pace of life in both vertebrate classes; and (4) is only weakly associated, if any, with the degree of sociality in both classes after accounting for the effect of body size and pace of life. However, when removing the effect of species differences in pace of life, a higher degree of sociality was associated with later and weaker reproductive senescence in females, which suggests that degree of sociality is either indirectly related to reproductive senescence via the pace of life or simply a direct outcome of the pace of life. Subject Areasecology, evolution

evolutionary biology↗

bioRxiv2020

Epigenetic clock and DNA methylation studies of roe deer in the wild

DNA methylation-based biomarkers of aging (epigenetic clocks) promise to lead to new insights in the evolutionary biology of ageing. Relatively little is known about how the natural environment affects epigenetic aging effects in wild species. In this study, we took advantage of a unique long-term (>40 years) longitudinal monitoring of individual roe deer (Capreolus capreolus) living in two wild populations (Chize and Trois Fontaines, France) facing different ecological contexts to investigate the relationship between chronological age and levels of DNA methylation (DNAm). We generated novel DNA methylation data from n=90 blood samples using a custom methylation array (HorvathMammalMethylChip40). We present three DNA methylation-based estimators of age (DNAm or epigenetic age), which were trained in males, females, and both sexes combined. We investigated how sex differences influenced the relationship between DNAm age and chronological age through the use of sex-specific epigenetic clocks. Our results highlight that both populations and sex influence the epigenetic age, with the bias toward a stronger male average age acceleration (i.e. differences between epigenetic age and chronological ages) particularly pronounced in the population facing harsh environmental conditions. Further, we identify the main sites of epigenetic alteration that have distinct aging patterns across the two sexes. These findings open the door to promising avenues of research at the crossroad of evolutionary biology and biogerontology.

evolutionary biology↗

bioRxiv2019

Population position along the fast-slow life-history continuum predicts intraspecific variation in actuarial senescence

Patterns of actuarial senescence can be highly variable among species. Previous comparative analyses revealed that both age at the onset of senescence and rates of senescence are linked to the species position along the fast-slow life-history continuum. As there are few long-term datasets of wild populations with known-age individuals, intraspecific (i.e. between-population) variation in senescence is understudied and limited to comparisons of wild and captive populations of the same species, mostly birds and mammals. In this paper, we examined how population position along the fast-slow life history continuum affects senescence patterns in an amphibian, Bombina variegata. We used capture-recapture data collected in four populations with contrasted life history strategies. Senescence trajectories were drawn using Bayesian capture-recapture models. We show that in \"slow\" populations the onset of senescence was earlier and individuals aged at a faster rate than individuals in \"fast\" populations. Our study provides one of the few empirical examples of between-population variation in senescence patterns in the wild and confirms that the fast-slow life history gradient is associated with both macroevolutionary and microevolutionary patterns of senescence.

ecology↗

bioRxiv2019

Slow life-history strategies are associated with negligible actuarial senescence in western Palearctic salamanders

Actuarial senescence (hereafter \"senescence\") has been viewed for a long time as an inevitable and uniform process. However, the work on senescence has mainly focused on endotherms (especially mammals) with deterministic growth and low regeneration capacity at adult stages, leading to a strong taxonomic bias in the study of aging. Recent studies have highlighted that senescence could indeed display highly variable trajectory shape that correlates with species life history traits. Slow life histories and indeterminate growth seem to be associated with weak and late senescence. Furthermore, a few studies have suggested that high regenerative abilities could make senescence negligible in several ectotherms (e.g., hydra and salamanders). However, demographic data for species that would allow testing of these hypotheses are scarce and fragmented. Here, we investigated senescence patterns in a group of salamanders (i.e. \"true salamanders\") from the Western Palearctic using capture-recapture data and Bayesian modeling. Our results showed that salamanders have slow life histories and that they experience negligible senescence. This pattern was consistent at both intra- and interspecific levels, suggesting that the absence of senescence may be a phylogenetically conserved trait. The regenerative capacities of true salamanders, and urodeles in general, likely explains why these small ectotherms have lifespans similar to that of large endotherms (e.g., ungulates, large birds) and undergo negligible senescence contrary to most amniotes including humans. Our study seriously challenges the idea that senescence is a ubiquitous phenomenon in the living world.

ecology↗

bioRxiv2019

Development of senescence biomarkers in the common woodlouse

Senescence, the decline of physiological parameters with increasing age, is a quasi-ubiquitous phenomenon in the living world. The observed patterns of senescence, however, can markedly differ across species and populations, between sexes, and even among individuals. To identify the drivers of this variation in senescence, experimental approaches are essential and involve the development of tools and new study models. Current knowledge of the senescence process is mostly based on studies on vertebrates and main information about senescence in invertebrates is mostly limited to model organisms such as Caenorhabditis elegans or Drosophila melanogaster. In this context, we tested whether biomarkers of vertebrate ageing could be used to study senescence in a new invertebrate model: the common woodlouse Armadillidium vulgare (Latreille, 1804). More specifically, we looked for the effect of age in woodlouse on three well-established physiological biomarkers of ageing in vertebrates: immune cells (cell size, density, and viability), {beta}-galactosidase activity, and the gene expression of telomerase reverse transcriptase (TERT), an essential subunit of telomerase protein. We found that the size of immune cells was higher in older individuals, whereas their density and viability decreased, and that the {beta}-galactosidase activity increased with age, whereas the TERT gene expression decreased. These findings demonstrate that woodlouse displays age-related changes in biomarkers of vertebrate senescence, with different patterns depending on gender. The tools used in studies of vertebrate senescence can thus be successfully used in studies of senescence of invertebrates such as the woodlouse. The application of commonly used tools to new biological models offers a promising approach to assess the diversity of senescence patterns across the tree of life.

evolutionary biology↗