Summary: 1. The assessment of species extinction risk has been well established for some time now. Assessing the potential for recovery in endangered species is however much more challenging, because complementary approaches are required to detect reliable signals of positive trends.2. This study combines genetics, demography and behavioural data at three different time‐scales to assess historical and recent population changes and evidence of reproductive synchrony in a small population of olive ridley sea turtle Lepidochelys olivacea. Lepidochelys is considered as the most extraordinary example of reproductive synchrony in reptiles, yet to date, it has only been reported in large populations.3. Using Bayesian coalescent‐based models on microsatellite nuclear DNA variability, we demonstrate that effective population size in olive ridleys nesting in French Guiana has dramatically declined by 99% over the last 20 centuries. This low current population size is further illustrated by the absence of genetic mitochondrial DNA diversity in the present nesting population. Yet, monitoring of nesting sites in French Guiana suggests a possible recovery of the population over the last decade.4. Satellite telemetry shows that over the first 14 days of their 28‐days inter‐nesting interval, i.e. when eggs maturation is likely to occur, gravid females disperse over the continental shelf. They then gather together with a striking spatiotemporal consistency close to the nesting site, where they later emerge for their second nesting event.5. Our results therefore suggest that reproductive synchrony also occurs in small populations. Olive ridleys may ensure this synchrony by adjusting the duration of the second half of their inter‐nesting interval prior to landing, possibly through social mediation.6. Such reproductive synchrony may be related to the maintenance of some species‐specific strategy despite former collapse and may contribute to the present population recovery. The gregarious behaviour of reproductive individuals close to shore where human‐induced perturbations occur is however a cause for conservation concern for this still poorly known species.

In the modern world, when the problems of the environment are most acutely associated with climate change, amphibians are considered to be the most vulnerable group of anamniotes as an indicator of the state of wetlands. Along with a decrease of numbers among amphibians in Europe, nowadays newts especially suffer from the impact of invasive species, in particular predators such as the Chinese sleeper, Perccottus glenii. This predatory fish species has recently spread to areas of primary relevance for newt reproduction. This fish consumes eggs, larvae, and even adult newt individuals. Using an ecological niche approach and climate based species distribution models (SDM), we applied the coefficient of determination (R²) for comparing the level of similarity of the built SDM for the newts Triturus cristatus and Lissotriton vulgaris, and the Chinese sleeper. We show that by 2050, the level of climatic niche similarity for these native and invasive species will increase from 12% to 22% throughout Europe, and from 44% to 66% in Eastern Europe. This study highlights the expansion of the Chinese sleeper as a real threat to European biodiversity of wetlands in the near future, especially in their most northeastern distribution range.

For ectotherms, behaviour and associated energetic costs are directly related to thermal conditions. In the present context of global change, estimating time-budget for these species is relevant to assess and predict their capacity to adapt to near future. We tested the hypothesis that in ectotherms where reproduction is highly energy consuming, energy expenditure should vary throughout the breeding season with a maximum around nesting events. To test this hypothesis, we assessed the fine-scale behaviour, time-budget and estimated energetic costs in eight adult female European pond turtlesEmys orbicularisequipped with data-loggers recording ambient temperature, pressure, light and the animals’ 3-axis acceleration. Deployments occurred over four months throughout the nesting season 2017 in semi-natural captive conditions in Alsace, France. All study turtles showed a clear daily pattern over the 24h cycle, with four distinct phases (referred to as Night, Morning, Midday and Evening), associated with different behaviours and activity levels. Before oviposition, turtles were mostly active during Morning, and activity was positively driven by ambient temperature. Activity levels doubled during the nesting period, mostly due to the increased activity in the Evening, when nesting events occurred. Throughout the active season, basking occurrence at Midday was related to air temperature but cloud coverage was an even more important factor. Our results are a first step in predicting the seasonal time and energy budgets of the European pond turtle, and demonstrate the usefulness of animal-borne accelerometers to study free living freshwater turtles over extended periods of time.

No biomarker has yet been discovered to identify the reproductive status of the endangered leatherback sea turtle (Dermochelys coriacea). Although vitellogenin (VTG) could be used for this, its sequence is not known in D. coriacea and no quantitative assay has been carried out in this species to date. Using de novo sequencing-based proteomics, we unambiguously characterized sequences of two different VTG isoforms that we named Dc-VTG1 and Dc-VTG2. To our knowledge, this is the first clear evidence of different VTG isoforms and the structural characterization of derived yolk proteins in reptiles. This work illustrates how massive de novo sequencing can characterize novel sequences when working on “exotic” nonmodel species in which even nucleotide sequences are not available. We developed assays for absolute quantitation of these two isoforms using selected reaction monitoring (SRM) mass spectrometry, thus providing the first SRM assays developed specifically for a nonsequenced species. Plasma levels of Dc-VTG1 and Dc-VTG2 decreased as the nesting season proceeded, and were closely related to the increased levels of reproductive effort. The SRM assays developed here therefore provide an original and efficient approach for the reliable monitoring of reproduction cycles not only in D. coriacea, but potentially in other turtle species.

Climate change has amplified the threat posed by aquatic invasive species as potential disruptors of biodiversity and ecosystem functioning. Species Distribution Models (MaxEnt) based on original data and ecological variables have identified contemporary seven global centers of the oriental rivel prawn Macrobrachium nipponense distribution: the native range in East Asia, Northern, Western and Eastern Europe, the Irano-Turanian region, and North and South America. By 2050, further expansion in Europe is expected, likely due to climate change, particularly temperature changes (Bio1) and rain precipitation during the warmest quarter (Bio18). However, the species may see a range reduction in southern Europe due to lower precipitation and increased droughts related to climate change. Therefore, a northward shift in the range of the species is also predicted. In the context of global change, and especially biological invasions, this study highlights the risks of introducing aquaculture based on M. nipponense and recommends controlling such economic activities, which are associated with a high risk for native species and ecosystems. Further, long-term monitoring is needed to assess impacts and to efficiently manage M. nipponense populations that are already present in their non-native habitats, for mitigating their negative effects on native species and ecosystems worldwide.

Les menaces qui pèsent sur la biodiversité conduisent à réfléchir sur le sens accordé au potentiel invasif d’espèces exogènes et aux modalités de leur gestion. La déconnexion des citadins de la nature complexifie les relations humains-non humains que nous invitons à penser en termes d’anthropologie multispécifique. Celle-ci interroge les formes de cohabitation du vivant et nous conduit à examiner les arbitrages concernant l’accueil ou l’exclusion d’espèces jugées envahissantes. Nous avons étudié les tortues exotiques présentes dans deux parcs de Strasbourg avec une double approche naturaliste et ethnologique. Plus de 60 individus de huit espèces de tortues exotiques ont été repérés au cours des étés 2017 et 2018. Les avis partagés sur la pertinence de leur présence révèlent un embarras certain des 87 informateurs. Les tortues représentent un facteur d’attraction et de reconnexion avec la nature, mais leur exotisme interroge ou inquiète. Il invite à confronter les valeurs qui leur sont attribuées pour reconsidérer les modalités de gestion de nos milieux. Une fois que les usagers des parcs sont informés par l’enquêteur sur l’origine et le potentiel envahissant en milieu naturel, la plupart préconisent l’extraction des individus vers des espaces dédiés, mais la perspective de leur destruction est globalement rejetée. L’analyse fine laisse pointer des postures nuancées ou perplexes sur la légitimité des humains à gouverner la nature. Plus largement, ce sont les rapports des urbains à la nature et à l’altérité que ces tortues permettent d’interroger.