Evaluating taxonomic inflation: towards evidence-based species delimitation in Eurasian vipers (Serpentes: Viperinae)

International audienceThe designation of taxonomic units has important implications for the understanding and conservation ofbiodiversity. Eurasian vipers are a monophyletic group of viperid snakes (Serpentes, Viperinae), currently comprising fourgenera (Daboia, Macrovipera, Montivipera and Vipera) and up to 40 species. Taxonomic units have been described usinga wide variety of methods and criteria, and consequently, considerable controversy still surrounds the validity of somecurrently listed species. In order to promote a consensus- and evidence-based taxonomy of Eurasian vipers, we analysedpublished mitochondrial and nuclear DNA sequences for this group to reconstruct phylogenetic relationships among currentlyrecognized viper species.We also compiled information on external morphology to assess their morphological distinctiveness.Phylogenetic inference based on mtDNA sequences shows contrasting levels of divergence across genera and species andidentifies several instances of non-monophyly in described species. Nuclear DNA sequences show extremely low levels ofgenetic variation, with a widespread pattern of allele sharing among distant species, and even among genera. Revision ofmorphological data shows that most species designations rely on scalation traits that overlap extensively among species ofthe same genus. Based on our combined assessment, we recognize 15 taxa as valid species, three taxa which likely representspecies complexes, 17 taxa of doubtful validity as species, and five taxa for which species status is maintained but furtherresearch is highly recommended to assess taxonomic arrangements. We stress the need to implement integrative taxonomicapproaches for the recognition of evidence-based taxonomic units in Eurasian viper

De la physiologie à la répartition (adaptations climatiques et sensibilité thermique chez une relique glaciaire)

L'un des objectifs majeurs en écologie est de comprendre les déterminants de la distribution des organismes. La répartition des espèces est le produit d'une réponse dynamique face à l'environnement biotique et abiotique. Il est primordial d'élaborer des inférences solides sur les contraintes pour identifier les facteurs proximaux de la distribution des espèces. Chez les ectothermes, la température corporelle est directement dépendante de la température ambiante qui va affecter la physiologie, le budget d'activité et par conséquent la plupart de leurs traits d'histoire de vie. La prévalence des facteurs abiotiques (climat) sur la distribution des espèces est largement pressentie notamment sur les espèces spécialisées dans l'économie d'énergie. Seul un petit nombre d'espèces d'ectothermes est capable d'exploiter des milieux froids ce qui soulève des questions sur leurs spécificités physiologiques et leurs réponses face aux changements globaux. Nous avons étudié l'écophysiologie et la distribution d'une espèce boréale, la vipère péliade (Vipera berus) dont l'aire de répartition très vaste trouve sa limite sud de répartition en France, dans le Massif Central. Nous avons réalisé des suivis comparatifs avec la vipère aspic (Vipera aspis), espèce sœur à répartition parapatrique limitée au Sud-ouest de l'Europe. Nos travaux sur la thermorégulation, le métabolisme, la sensibilité hydrique et la phénologie de reproduction montrent que l'espèce boréale présente des adaptations spécifiques au froid qui la rendent particulièrement vulnérable aux températures élevées notamment en période estivale. Nos résultats de modélisation corrélative soulignent clairement que le climat est suffisant pour prédire la majeure partie de la répartition des espèces. En parallèle, les modèles de niches physiologiques démontrent l'importance de la dépendance thermique des coûts de maintenance et de la phénologie de la reproduction. En effet, les limites Sud de distributions des deux espèces seraient liées à des contraintes énergétiques et hydriques trop fortes alors que l'altération des performances reproductrices limiterait V aspis au Nord. Les variations climatiques passées (cycles glaciaire/interglaciaire) ont largement impacté la structuration génétique des populations de vipère péliade. Les scenarios de changements climatiques futurs pourraient avoir un impact majeur sur la persistance de l'espèce d'ici 2100 dans les landes et tourbières en zone amont de la Loire.A major goal in ecology is to understand the determinants of species distribution. Species distributions result from a dynamic response to biotic and abiotic factors. It is of crucial importance to idenfity limiting factors and their relevance, to identify proximate factors shaping species distributions. In ectotherms, ambient temperature directly influences body temperature and therefore affects physiology, activity budget, and most life history traits. Consequently, abiotic factors (climate) should have a prevalent influence on the distribution of ectotherms. Few species are able to exploit cold climates, raising the problem of their physiological specificities and responses to global change. We studied the ecophysiology and distribution of a boreal species, the adder (Vipera berus). This geographically widespread species (Eurosiberian) meets its southern limit in France (Massif Central). We compared V. berus with the asp viper (Vipera aspis), a sister species with a parapatric distribution limited to southwestern Europe. Our work on thermoregulation, metabolism, hydric sensitivity, and reproductive phenology reveals specific cold adaptations in V. berus that make this species vulnerable to high temperatures, especially during summer. Correlative modeling indicated that climate largely explains the species' distribution. In parallel, mecanistic niche modeling demonstrated the importance of thermal dependence of maintenance costs and reproductive phenology. For instance, southern distribution limits in both species are linked to energetic and hydric constraints while northern limits in V aspis likely involve altered reproductive performance. Past climatic variations (glacial/interglacial periods) have strongly affected the genetic structure of adder populations. Scenarios of future climate change are likely to impact the persistence of this species by 2100 in heathland and peat bogs in the Loire upstream zone.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Stratégies de thermorégulation chez deux colubridés sympatriques,la couleuvre verte et jaune Hierophis viridiflavus et la couleuvre d'Esculape Zamenis longissimus (une approche intégrée de la physiologie à la démographie)

La température est un paramètre clé qui façonne de nombreuses adaptations physiologiques, morphologiques et comportementales des animaux. Chez les ectothermes, la thermorégulation est majoritairement comportementale et résulte d'un compromis entre les bénéfices et les coûts associés. Généralement, l'augmentation de la température corporelle améliore les performances et permet d'optimiser des processus tels que la digestion, la croissance ou la reproduction. Cependant, la thermorégulation comporte aussi des coûts (dépense énergétique, risque de prédation, allocation du temps). De plus, les orientations thermiques peuvent avoir de profondes implications sur les budgets énergétiques, le comportement et à terme, les dynamiques de population d'ectothermes. Ces mécanismes ont pu être abordés chez des organismes à démographie rapide comme les insectes, mais ont été peu explorés chez les vertébrés ectothermes terrestres (reptiles et amphibiens). Au cours de cette thèse, nous avons examiné un couple d'espèces de serpents en coexistence : la couleuvre verte et jaune Hierophis viridiflavus et la couleuvre d'Esculape Zamenis longissimus. Nous avons mis en évidence un fort contraste d'adaptation thermique entre ces espèces. L'étude intégrée de leur physiologie, leur comportement et leur démographie a permis de révéler les liens existant entre les différents niveaux, de l'individu à la population, et comment ces liens forment de véritables syndromes adaptatifs. Les résultats obtenus soulignent comment les adaptations thermiques affectent les réponses démographiques par l'intermédiaire de processus physiologiques, mais également l'influence des conditions environnementales (fluctuations thermiques, ressources trophiques, structure de l'habitat) sur l'efficacité relative de stratégies contrastées.Temperature affects most traits in animals, from physiological, morphological, and behavioural adaptations. In ectotherms, thermoregulation primarily involves behaviour. The optimal level of thermoregulation results from a trade-off between associated costs and benefits. Generally, an elevation of the body temperature improves physiological performance, but implies costs in terms of energy expended, increased predation risk, and time spent. Thermal adaptation may therefore influence energetics, behavioural strategies, and ultimately, population dynamics of ectotherms. These processes have been studied in invertebrates with short generation times, but rarely in terrestrial ectothermic vertebrates (reptiles and amphibians). We explored these processes in two sympatric colubrids, the European whip snake Hierophis viridiflavus and the Aesculapian snake Zamenis longissimus. These two species diverged markedly in thermal strategy. Our integrative study from physiological and behavioural adaptation, to demographic responses revealed tight links between thermal adaptation and population dynamics, hence illustrating contrasted adaptive syndromes. Our results also underlie the importance of environmental conditions in modulating the relative efficiency of each strategy.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Reproductive state and water deprivation increase plasma corticosterone in a capital breeder

International audiencePlasma corticosterone (CORT) concentrations fluctuate in response to homeostatic demands. CORT is widely recognized as an important hormone related to energy balance. However, far less attention has been given to the potential role of CORT in regulating salt and water balance or responding to osmotic imbalances. We examined the effects of reproductive and hydric states on CORT levels in breeding Children’s pythons (Antaresia childreni), a species with substantial energetic and hydric costs associated with egg development. Using a 2 × 2 experimental design, we examined how reproduction and water deprivation, both separately and combined, impact CORT levels and how these changes correlate with hydration (plasma osmolality) and energy levels (blood glucose). We found that reproduction leads to increased CORT levels, as does dehydration induced by water deprivation. The combined impact of reproduction and water deprivation led to the largest increases in CORT levels. Additionally, we found significant positive relationships among CORT levels, plasma osmolality, and blood glucose. Our results provide evidence that both reproductive activity and increased plasma osmolality can lead to increased plasma CORT in an ectotherm, which could be explained by either CORT having a role as a mineralocorticoid or CORT being elevated as part of a stress response to resource imbalances

When Does a Reproducing Female Viper (\u3cem\u3eVipera aspis\u3c/em\u3e) ‘Decide’ on her Litter Size?

Some organisms rely on stored energy to fuel reproductive expenditure (capital breeders) whereas others use energy gained during the reproductive bout itself (income breeders). Most species occupy intermediate positions on this continuum, but few experimental data are available on the timescale over which food intake can affect fecundity. Mark–recapture studies of free-ranging female aspic vipers Vipera aspis have suggested that reproductive output relies not only on the energy in fat bodies accumulated in previous years, but also on food intake immediately before ovulation. A simple experiment was conducted to test this hypothesis, maintaining female snakes in captivity throughout the vitellogenic period and controlling their food intake. The energy input of a female strongly influenced the amount of mass that she gained and the number of ova that she ovulated. Multiple regression showed that litter size in these snakes was affected both by maternal body condition in early spring (an indicator of foraging success over previous years) and by food intake in the spring before ovulation. Our experimental data thus reinforce the results of descriptive studies on free-ranging snakes, and emphasize the flexibility of energy allocation patterns among vipers. Reproducing female vipers may combine energy from ‘capital’ and ‘income’ to maximize their litter sizes in the face of fluctuating levels of prey abundance

Snake conservation in anthropized landscapes: considering artificial habitats and questioning management of semi-natural habitats

The intensification of human activities is responsible for habitat loss which is the major cause of biodiversity regression. In this context, it becomes critical to consider with more attention highly transformed or artificial habitats that may have a significant value for biodiversity conservation. It is also equally important to evaluate the significance of management measures in remaining semi-natural habitat. Squamate reptiles (lizards and snakes) usually have limited dispersal capacities and are consequently particularly vulnerable to habitat changes. We studied the abundance of an endangered species, the smooth snake (Coronella austriaca), in 112 sites located in the southern part of Belgium. We wanted to compare population size and density in a semi-natural habitat (dry grassland) and two artificial ones (rocky habitats and railway). We also wanted to compare snake density in grasslands depending on management measures (either mowing, grazing, or no management). Our results suggest that smooth snake population sizes are low with fewer than 20 individuals on 85% of the sampled sites. Highest density and population sizes were reported along railways and in artificial rocky habitats when compared with grasslands. Population density was lower in nature reserves reflecting notably the negative effect of management (grazing). Our study suggests that transformed habitat can provide significant structural diversity and can be beneficial as long as human pressure remains low. In turn, management measures deployed in semi-natural habitats may dramatically affect microhabitat diversity and significantly impact squamate populations

Stratégie reproductrice d'une espèce de lézard à pontes multiples (Podarcis muralis) dans un environnement contraignant

Les êtres vivants sont exposés aux variations environnementales (notamment thermiques) à l'échelle journalière, saisonnière ou annuelle. Chez les ectothermes, la température du milieu affecte directement la température corporelle et donc la physiologie, les performances locomotrices, l'activité et de façon ultime la "fitness" des individus. Le développement embryonnaire est une étape très sensible aux fluctuations thermiques et les ectothermes ont déployé une diversité de moyens pour en atténuer les effets. Chez les espèces à pontes annuelles multiples, la reproduction s'étale sur une période étendue pendant laquelle les conditions thermiques saisonnières varient fortement. Ces fluctuations peuvent profondément contraindre l'activité des individus et affecter les trajectoires de développement. Les déterminants du succès reproducteur impliquent donc la prise en compte des contraintes environnementales mais aussi de l'ontogénie des individus. En effet, chez les espèces à croissance indéterminée, la nature des compromis d'allocation devrait fortement dépendre de la taille et de l'âge des individus. Des changements ontogéniques dans les stratégies d'allocation de la ressource sont attendus en permettant une optimisation du succès reproducteur. Au cours de cette thèse, nous avons examiné les stratégies de reproduction chez une espèce à pontes multiples, le lézard des murailles (Podarcis muralis) dans un contexte thermique contraignant (climat océanique, Centre Ouest de la France). A l'aide d'une approche expérimentale, nous avons mis en évidence le fort impact des conditions thermiques sur la qualité du développement embryonnaire et l'importance de la phénologie (date de ponte) sur les trajectoires individuelles. Les dates de ponte précoces et les températures d'incubation élevées favorisent la survie des jeunes. Le suivi CMR lancé en 2006 a permis de mettre en évidence l'importance de l'âge et de la taille corporelle des femelles dans le compromis d'allocation. Ainsi les individus âgés cessent d'allouer leurs ressources dans la croissance et favorisent la capitalisation de l'énergie. Cette transition permet de soutenir un effort reproducteur plus élevé et un engagement plus précoce dans la reproduction. Des contraintes énergétiques induites par la reproduction ont également pu être révélées en étudiant les variations saisonnières des taux de corticoïdes et de l'ectoparasitisme. Enfin l'étude de la multipaternité souligne l'influence de la taille des femelles et de la séquence de ponte sur la stratégie de reproduction.Living organisms are exposed to environmental fluctuations (including temperature) at the daily, seasonal or annual scale. In ectotherms, environmental temperature directly affects body temperature and thus the physiology, locomotory performance, activity and ultimately the fitness of individuals. Embryonic development is a very sensitive step to thermal fluctuations and ectotherms have deployed a variety of means to buffer its effects. In annual multiple clutches species, reproduction spread over an extended period during which the seasonal thermal conditions vary widely. These fluctuations can profoundly constrain the activity of the individuals and affect developmental trajectories. Determinants of reproductive success thus involve the consideration of environmental constraints as well as ontogéniques trajectories. Indeed, in indeterminate growth species, the nature of allocation trade-offs should strongly depends on the size and age of the individuals. Ontogenetic changes in strategies for resource allocation are expected to optimize reproductive success. In this thesis, we examined the reproductive strategies in a species with multiple clutches, the wall lizard (Podarcis muralis) in a thermally challenging context (oceanic climate, Central West of France). Using an experimental approach, we demonstrated the strong impact of thermal conditions on the quality of embryonic development and the importance of phenology (laying date) on individual trajectories. Early laying dates and incubation temperatures promote high survival of juveniles. The population monitoring initiated in 2006 has highlighted the importance of age and body size of females in the allocation trade-offs. Thus older individuals cease to allocate their resources in growth and encourage the capitalization of energy. This ontogenic shift supports a higher reproductive effort and a earlier engagement in reproduction. Energy constraints induced by reproduction have also been revealed by studying the seasonal variations in levels of corticosteroids and ectoparasites. Finally the study of multipaternity emphasizes the influence of female size and laying sequence on the reproductive strategy.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Small changes, big benefits: testing the significance of maternal thermoregulation in a lizard with extended egg retention (Zootoca vivipara)

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Amphibian diversity in farmlands: Combined influences of breeding-site and landscape attributes in western France

International audienceAgricultural intensification is responsible for major habitat degradation and is a primary cause of biodiversity loss. Amphibians are currently facing a global decline induced by multiple pressures, including notably habitat degradation and land conversion. In western Europe, traditional farming systems involve a dense hedgerow network with a mosaic of pastures, cultivated fields, ponds, and small woods. These heterogeneous landscapes are particularly favorable for biodiversity but their role for amphibian conservation remain understudied.We studied the amphibian community (15 species) of a hedgerow network landscape in western France. We described 79 cattle ponds and tested the influence of ponds characteristics as well as the surrounding landscape composition on species occurrence. Amphibian diversity was positively influenced by breeding site vegetation and also ponds density in the surrounding landscape. We also found positive effects of wood patches and hedgerow linear at a small spatial scale. In turn, crop cover and road linear negatively influenced amphibian richness at large spatial scale. Important variation were detected among species reflecting contrasted life history traits. Our results underline that traditional pastoral landscapes provide a high density of breeding sites and habitats favorable for a diversity of amphibian species