When does early-life telomere length predict survival?:A case study and meta-analysis

Suboptimal conditions during development can shorten telomeres, the protective DNA caps on the end of chromosomes. Shorter early-life telomere length (TL) can indicate reduced somatic maintenance, leading to lower survival and shorter lifespan. However, despite some clear evidence, not all studies show a relationship between early-life TL and survival or lifespan, which may be due to differences in biology or study design (e.g., survival period measured). In superb fairy-wrens (Malurus cyaneus), we assessed whether early-life TL predicts mortality across different life-history stages (fledgling, juvenile, adult). However, in contrast to a similar study on a congener, early-life TL did not predict mortality across any life stage in this species. We then performed a meta-analysis including 32 effect sizes from 23 studies (15 birds and 3 mammals) to quantify the effect of early-life TL on mortality whilst taking into consideration potential sources of biological and methodological variation. Overall, the effect of early-life TL on mortality was significant, corresponding to a 15% reduction in mortality risk with each standard deviation increase in TL. However, the effect became weaker when correcting for publication bias. Contrary to our predictions, there was no evidence that effects of early-life TL on mortality varied with species lifespan or the period over which survival was measured. However, negative effects of early-life TL on mortality risk were pervasive throughout life. These results imply that effects of early-life TL on mortality are more likely context-dependent rather than age-dependent, although substantial power and publication bias issues highlight the need for more research.Funding provided by: Australian Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000923Award Number

Importance of water-based tradeoffs in a reptile using ecotone habitats, the Aspic viper (Vipera aspis)

L'un des enjeux majeurs en écologie est de comprendre et prédire la réponse des organismes aux variations environnementales. Pour cela, la clarification des mécanismes proximaux est une étape indispensable pour comprendre des patrons écologiques généraux comme l'utilisation de l'habitat ou la distribution des espèces. Dans ce contexte, l'approche écophysiologique est particulièrement pertinente. Si la ressource trophique et les contraintes énergétiques ont attiré un intérêt considérable, les compromis liés à l'eau demeurent actuellement peu considérés. Pourtant l'eau est aussi une ressource capitale pouvant être limitante. La régulation de la balance hydrique pourrait donc jouer un rôle clé dans les compromis physiologiques et comportementaux.L'objectif principal de ce doctorat est d'évaluer l'importance des compromis liés à l'eau chez une espèce caractéristique des milieux bordiers (haies, lisières), la vipère aspic (Vipera aspis). Cette espèce vivipare est particulièrement dépendante des conditions thermiques, notamment pour sa reproduction. Notre hypothèse générale est qu'au même titre que les conditions thermiques, les conditions hydriques confrontent l'organisme à des compromis physiologiques et comportementaux importants, particulièrement lors de la reproduction (i.e., gestation). Nous avons combiné des études descriptives (thermorégulation, pertes hydriques) et expérimentales (manipulation de l’accès à l'eau) qui suggèrent l'existence d'un compromis entre la thermorégulation et la balance hydrique. Ces contraintes liées à l'eau sont associées à des ajustements physiologiques et comportementaux qui doivent être considérés pour comprendre les stratégies reproductrices et identifier de possibles conflits intergénérationnels (mère-embryons). Au même titre que les contraintes énergétiques ou thermiques, les besoins en eau sont donc essentiels à considérer pour aborder des questions écologiques et évolutives générales.A major goal in ecology is to understand and predict species responses to environmental variations. Clarifying the proximate factors involved is a crucial step to unravel general ecological patterns such as habitat use or species distribution. In this context, the use of an ecophysiological approach can be particularly relevant. Trophic resource and energy tradeoffs attracted considerable interest but water-based tradeoffs remain relatively overlooked to date. However water is a critical, often limiting resource that must be considered. The regulation of water balance may have a key influence on physiological and behavioral tradeoffs. The main objective in this thesis is to evaluate the importance of water-based tradeoffs in a species characteristic of "ecotone" habitats (hedgerows, edges), the Aspic viper (Vipera aspis). This species is viviparous and highly depends on thermal conditions during reproduction. Our general hypothesis is that, as thermal conditions, hydric conditions should expose individuals to important physiological and behavioral tradeoffs, especially during reproduction (i.e., pregnancy).We combined descriptive (thermoregulation, water losses) and experimental studies (manipulation of water availability) that suggest a significant tradeoff between thermoregulation and water balance regulation. Water-based tradeoffs induce physiological and behavioral adjustments that are relevant to understand reproductive strategies and identify possible transgenerational (mother-embryos) conflicts. As energy or thermal resource, water should therefore also be considered to address ecological or evolutive questions

Importance des compromis liés à l’eau chez une espèce caractéristique des milieux bordiers, la vipère aspic (Vipera aspis)

A major goal in ecology is to understand and predict species responses to environmental variations. Clarifying the proximate factors involved is a crucial step to unravel general ecological patterns such as habitat use or species distribution. In this context, the use of an ecophysiological approach can be particularly relevant. Trophic resource and energy tradeoffs attracted considerable interest but water-based tradeoffs remain relatively overlooked to date. However water is a critical, often limiting resource that must be considered. The regulation of water balance may have a key influence on physiological and behavioral tradeoffs.The main objective in this thesis is to evaluate the importance of water-based tradeoffs in a species characteristic of “ecotone” habitats (hedgerows, edges), the Aspic viper (Vipera aspis). This species is viviparous and highly depends on thermal conditions during reproduction. Our general hypothesis is that, as thermal conditions, hydric conditions should expose individuals to important physiological and behavioral tradeoffs, especially during reproduction (i.e., pregnancy).We combined descriptive (thermoregulation, water losses) and experimental studies (manipulation of water availability) that suggest a significant tradeoff between thermoregulation and water balance regulation. Water-based tradeoffs induce physiological and behavioral adjustments that are relevant to understand reproductive strategies and identify possible transgenerational (mother-embryos) conflicts. As energy or thermal resource, water should therefore also be considered to address ecological or evolutionary questions.L’un des enjeux majeurs en écologie est de comprendre et prédire la réponse des organismes aux variations environnementales. Pour cela, la clarification des mécanismes proximaux est une étape indispensable pour comprendre des patrons écologiques généraux comme l’utilisation de l’habitat ou la distribution des espèces. Dans ce contexte, l’approche écophysiologique est particulièrement pertinente. Si la ressource trophique et les contraintes énergétiques ont attiré un intérêt considérable, les compromis liés à l’eau demeurent actuellement peu considérés. Pourtant l’eau est aussi une ressource capitale pouvant être limitante. La régulation de la balance hydrique pourrait donc jouer un rôle clé dans les compromis physiologiques et comportementaux.L’objectif principal de ce doctorat est d’évaluer l’importance des compromis liés à l’eau chez une espèce caractéristique des milieux bordiers (haies, lisières), la vipère aspic (Vipera aspis). Cette espèce vivipare est particulièrement dépendante des conditions thermiques, notamment pour sa reproduction. Notre hypothèse générale est qu’au même titre que les conditions thermiques, les conditions hydriques confrontent l’organisme à des compromis physiologiques et comportementaux importants, particulièrement lors de la reproduction (i.e., gestation).Nous avons combiné des études descriptives (thermorégulation, pertes hydriques) et expérimentales (manipulation de l’accès à l’eau) qui suggèrent l’existence d’un compromis entre la thermorégulation et la balance hydrique. Ces contraintes liées à l’eau sont associées à des ajustements physiologiques et comportementaux qui doivent être considérés pour comprendre les stratégies reproductrices et identifier de possibles conflits intergénérationnels (mère-embryons). Au même titre que les contraintes énergétiques ou thermiques, les besoins en eau sont donc essentiels à considérer pour aborder des questions écologiques et évolutives générales

Effects of mild wintering conditions on body mass and corticosterone levels in a temperate reptile, the aspic viper (Vipera aspis)

International audienceTemperate ectotherms are expected to benefit fromclimate change (e.g., increased activity time), but the impactsof climate warming during the winter have mostly been overlooked. Milder winters are expected to decreasebody condition upon emergence, and thus to affect crucial life-history traits, such as survival and reproduction.Mildwinter temperature could also trigger a state of chronic physiological stress due to inadequate thermal conditionsthat preclude both dormancy and activity. We tested these hypotheses on a typical temperate ectothermicvertebrate, the aspic viper (Vipera aspis). We simulated different wintering conditions for three groups ofaspic vipers (cold: ~6 °C, mild: ~14 °C and no wintering: ~24 °C) during a one month long period. We foundthat mild wintering conditions induced a marked decrease in body condition, and provoked an alteration ofsome hormonal mechanisms involved in emergence. Such effects are likely to bear ultimate consequences on reproduction,and thus population persistence. We emphasize that future studies should incorporate the critical,albeit neglected, winter season when assessing the potential impacts of global changes on ectotherms

Traffic noise decreases nestlings’ metabolic rates in an urban exploiter

International audienceHigh levels of anthropogenic noise produced in urban areas are known to negatively aff ect wildlife. Although most researchhas been focused on the disturbances of communication systems, chronic noise exposure can also lead to physiologicaland behavioural changes that have strong consequences for fi tness. For instance, behavioural changes mediated byanthropogenic noise (e.g. quality of parental care) may alter development and could infl uence nestling phenotype. Wetested if nestling metabolism was infl uence by traffi c noise in an urban exploiter, the house sparrow Passer domesticus .We experimentally exposed breeding house sparrows from a rural area to a playback of traffi c noise and we examinedthe impacts of this experimental procedure on metabolic rates and morphology of nestlings. We did not fi nd an eff ect oftraffi c noise on the morphology of nestlings. Surprisingly, we found that disturbed nestlings had overall lower metabolicrates and mass-adjusted metabolic rates than undisturbed birds. Our results suggest a specifi c eff ect of noise exposureper se, rather than an indirect eff ect of anthropogenic noise through the quality of parental care. Both the proximatemechanisms and the ultimate consequences of such metabolic changes on nestlings remain unknown and deserve futureexperimental studies

Cool, dry nights and short heatwaves during growth result in longer telomeres in temperate songbird nestlings

Abstract Exposure to rising sublethal temperatures can affect development and somatic condition, and thereby Darwinian fitness. In the context of climate warming, these changes could have implications for population viability, but they can be subtle and consequently difficult to quantify. Using telomere length (TL) as a known biomarker of somatic condition in early life, we investigated the impact of pre‐hatching and nestling climate on six cohorts of wild nestling superb fairy wrens ( Malurus cyaneus ) in temperate south‐eastern Australia. Models incorporating only climate information from the nestling phase were best supported compared to those including the (pre‐)laying to incubation phase (previously shown to affect mass) or both phases combined. This implies that nestling TL is most sensitive to ambient climate in the nestling phase. The top model showed a negative relationship between early‐life TL and nestling mean daily minimum temperature when rainfall was low which gradually became positive with increasing rainfall. In addition, there was a positive relationship between TL and the frequency of hot days (daily maximum temperature ≥35°C), although these temperatures were rare and short‐term. Including other pre‐hatching and nestling period, climate variables (e.g., mean daily maximum temperature and mean diurnal temperature variability) did not improve the prediction of nestling TL. Overall, our results suggest that cooler nights when conditions are dry and short‐term temperature spikes above 35°C during development are conducive for somatic maintenance. While these findings indicate a potential pathway for climate warming to impact wildlife fitness, they emphasize the need to elucidate the mechanisms underlying these complex associations

Cold tolerance and sex-dependent hypothermia may explain winter sexual segregation in a farmland bird

International audienceMigration is an important event in the life cycle of many organisms, but considerable intraspecific variation may occur in its timing and/or destination, resulting in sexual segregation during wintering periods. In this study, we tested the body size hypothesis, or cold tolerance hypothesis, which predicts that body size dimorphism modulates metabolic costs associated with cold climate. Using the Eurasian skylark, we first investigated whether this species showed sexual differential migration. Then we explored the body size hypothesis by experimentally testing the effect of low ambient temperature (Ta) on both metabolic rate (MR) and body temperature (Tb). We tested for sex-related differences in metabolism and in energy-saving mechanism (hypothermia). We found clear differential migration by sex in skylark wintering populations, with a male-biased sex ratio decreasing toward southern latitudes. Measurements on captive birds at 20°, 6°, and −5°C demonstrated a significant increase in MR when Ta decreased, but there is no difference between sexes. While both males and females reduced their Tb overnight, Tb reduction was more pronounced in females exposed to the coldest temperature treatment. In addition, we found that individuals with the most reduced Tb lost less body weight during the night, suggesting that Tb reduction may help minimize energy expenditure when conditions become constraining. Our study suggests that functional mechanisms may be involved in latitudinal segregation between sexes and supports the hypothesis that sex-specific physiological strategies and thermal tolerance may explain segregation between sexes

Colouration matters in dull toads: ultraviolet adornment for ladies and agrochemicals fading effects

International audienceIntegument colouration can influence many aspects of fitness, and is under strong sexual selection. Amphibians often express sexual dichromatism, and ultra-violet (UV) colouration is usually biased toward males as a sexual signal. As an honest signal, colouration is related to several individual traits, but can also be related to environmental factors such as anthropogenic pollutants, to which amphibians are highly sensitive. In this study, we investigated sexual dichromatism and UV reflectance covering a large visual spectrum (wavelength ranging from 300 to 700 nm) on different body areas (throat, ventral and dorsal areas), in a widespread amphibian species, the spiny toad (Bufo spinosus). Then, we tested the impact of chronic exposure to two widespread herbicides (glyphosate’s primary metabolite [AMPA] and Nicosulfuron) on their colouration. We found a strong but unexpected sexual dichromatism with females reflecting more in the UV spectrum (throat and ventral area) than males, suggesting these body parts might be critical in intra-specific signalling. Females with higher ventral UV reflectance were in better body condition, suggesting an honest signal role of UV reflectance which could influence male choice. Throat colouration was further differentially influenced by agrochemicals according to sexes. In AMPA-exposed males, throat was more saturated in yellow-orange than in control males, and Nicosulfuron exposure decreased the throat’s reflectance hue in females, which can bear consequences on mate attractiveness. Future studies need to investigate the underlying mechanisms that are altered by agrochemical exposure

Background noise decreases nestlings’ metabolic rates in an urban exploiter

International audienc

No effect of testosterone or sexual ornamentation on telomere dynamics:A case study and meta-analyses

Life-history theory predicts that reproductive investments are traded-off against self-maintenance. Telomeres, the protective caps on the ends of chromosomes, offer a promising avenue for assessing life-history trade-offs, as they shorten in response to stressors and are predictive of the remaining lifespan. In males, testosterone frequently mediates life-history trade-offs, in part, through its effects on sexual ornamentation, which is an important aspect of reproductive investment. However, studies of within-individual associations between telomere dynamics and sexual ornamentation are limited in number and have produced mixed results. Furthermore, most such studies have been observational, making it difficult to discern the nature of any causal relationship. To address this, we used short-acting testosterone implants in free-living male superb fairy-wrens (Malurus cyaneus) to stimulate the production of a sexual ornament: early moult into a costly blue breeding plumage. We found no evidence that elevated testosterone, and the consequent earlier moult into breeding plumage, accelerated telomere shortening. We therefore followed up with a systematic review and two meta-analyses (28 studies, 54 effect sizes) exploring the associations between telomeres and (1) testosterone and (2) sexual ornamentation. In line with our experimental findings, neither meta-analysis showed an overall correlation of testosterone or sexual ornamentation with telomere length or telomere dynamics. However, meta-regression showed that experimental, compared to observational, studies reported greater evidence of trade-offs. Our meta-analyses highlight the need for further experimental studies to better understand potential responses of telomere length or telomere dynamics to testosterone or sexual ornamentation. </p