Transport infrastructure severely impacts amphibian dispersal regardless of life stage

International audienceTransport infrastructure such as roads has been reported to negatively affect dispersal. Their effects on dispersal are thought to be complex, depending on the characteristics of the structure and the intensity of the traffic using it. In addition, individual factors, such as age, may strongly affect dispersal decisions and success when individuals are confronted with transport infrastructure. Despite the importance of this topic for wildlife conservation, few studies have investigated the effect of transport infrastructure on individuals’ dispersal decisions before and after sexual maturity. We examined the effects on two kinds of infrastructure, gravel tracks and paved roads, on the dispersal of an endangered amphibian, the yellow-bellied toad (Bombina variegata). We used capture–recapture data collected during a five-year period on a large, spatially structured population of B. variegata. Our study revealed that emigration rates increased with an individual’s age, while dispersal distance decreased. It also showed that both tracks and roads had negative effects on immigration. The negative effect of roads was stronger than that of tracks. We additionally found that the effect of tracks on dispersal slightly decreased with a toad’s age. In contrast, the negative effect of roads was severe and relatively similar across age classes

Gestion forestière et dynamique des populations de Sonneurs à ventre jaune (Bombina variegata): synthèse bibliographique et mesures de conservation: Forest management and population dynamics of the Yellow-bellied Toad (Bombina variegata): bibliographic review and conservation measures

International audienceDuring the 20th century, yellow-bellied toad (Bombina variegata) populations suffered from a strong decline in western Europe, especially in France. The causes of this decline are potentially multiple, including habitat loss and fragmentation, and climate change. To date, production forests host the largest yellow-bellied toad populations in France. Conservation of this species is thus tightly linked to forest management practices. During the last decade, intensification of forest harvesting led to the increasing systematic removal of ruts, the preferential breeding habitat of yellow-bellied toad in production forests. Enstonement of forest paths and timber storage areas, and the rapid filling of ruts after forest harvesting, are potential causes of decline for this species. Here, we synthetize the results of papers focusing on the impact of forest management practices on yellow-bellied toad population dynamics. We started our review paper with a comparative demographic analysis between populations from riverine habitat and production forest. After highlighting the demographic characteristics of forest populations, we documented the influence of path enstonement and road pavement on yellow-bellied toad dispersal. We also reported the effect of rut patch destruction on adult survival and long-term population viability. In the light of scientific evidences gathered in our synthesis, we concluded that these forest management practices pose a major threat for forest populations viability and persistence. We proposed a set of management practices aimed at better alignment of forestry activities and yellow-bellied toad conservation in French production forests.Durant le 20ème siècle, les populations de Sonneurs à ventre jaune (Bombina variegata) ont subi un net déclin en Europe de l’Ouest, et en France tout particulièrement. Les causes de cette régression sont possiblement multiples, incluant la perte et la fragmentation d’habitat, ainsi que les changements climatiques. De nos jours, les forêts de production de bois abritent les plus grandes populations de Sonneurs à ventre jaune du territoire. La conservation de cette espèce apparait donc étroitement dépendante des pratiques de gestion forestière. Depuis une dizaine d’années, l’intensification de l’exploitation forestière favorise l’élimination de plus en plus systématique des ornières, lesquelles constituent l’habitat de reproduction préférentiel du Sonneur à ventre jaune en forêt de production. L’empierrement des chemins forestiers et des places de dépôt de bois, ainsi qu’une tendance au comblement rapide des ornières après l’exploitation des parcelles, constituent des causes potentielles de déclin pour cette espèce. Dans cet article, nous effectuons une synthèse des travaux s’intéressant aux impacts des pratiques de gestion forestière sur la dynamique des populations de Sonneurs à ventre jaune en France. Nous débutons par une analyse de démographie comparée entre les populations d’environnements rivulaires et celles de forêts de production. Après avoir mis en évidence les particularités démographiques des populations forestières, nous rapportons les effets de l’empierrement et du goudronnage des chemins forestiers sur la dispersion. Puis, nous documentons l’effet de la destruction des patchs d’ornières sur la survie des adultes et la viabilité à long terme des populations. Sur la base des faits scientifiques rassemblés dans cette synthèse, il résulte que ces pratiques de gestion font courir un risque majeur pour la viabilité des populations en forêt. Nousproposons une série de préconisations de gestion visant à assurer une meilleure adéquation entre les travaux forestiers et la conservation du Sonneur à ventre jaune dans les forêts de production françaises

Estimating dispersal in spatiotemporally variable environments using multievent capture-recapture modeling

International audienceDispersal is a key process in ecological and evolutionary dynamics. Spatiotemporal vari- ation in habitat availability and characteristics has been suggested to be one of the main cause involved in dispersal evolution and has a strong influence on metapopulation dynamics. In recent dec- ades, the study of dispersal has led to the development of capture–recapture (CR) models that allow movement between sites to be quantified, while handling imperfect detection. For studies involving numerous recapture sites, Lagrange et al. (2014) proposed a multievent CR model that allows disper- sal to be estimated while omitting site identity by distinguishing between individuals that stay and individuals that move. More recently, Cayuela et al. (2017) extended this model to allow survival and dispersal probabilities to differ for the different types of habitat represented by several sites within a study area. Yet in both of these modeling systems, the state of sites is assumed to be static over time, which is not a realistic assumption in dynamic landscapes. For that purpose, we generalized the multi- event CR model proposed by Cayuela et al. (2017) to allow the estimation of dispersal, survival and recapture probabilities when a site may appear or disappear over time (MODEL 1) or when the char- acteristics of a site fluctuate over space and time (MODEL 2). This paper first presents these two new modeling systems, and then provides an illustration of their efficacy and usefulness by applying them to simulated CR data and data collected on two metapopulations of amphibians. MODEL 1 was tested using CR data recorded on a metapopulation of yellow-bellied toads (Bombina variegata). In this first empirical case, we examined whether the drying-out dynamics of ponds and the past dispersal status of an individual might affect dispersal behavior. Our study revealed that the probability of facul- tative dispersal (i.e., from a pond group that remained available/flooded) fluctuated between years and was higher in individuals that had previously dispersed. MODEL 2 was tested using CR data collected on a metapopulation of great crested newts (Triturus cristatus). In this second empirical example, we investigated whether the density of alpine newts (Ichthyosaura alpestris), a potential competitor, might affect the dispersal and survival of the crested newt. Our study revealed that the departure rate was lower in ponds with a high density of heterospecifics than in ponds with a low density of heterospeci- fics at both inter-annual and intra-annual scales. Moreover, annual survival was slightly higher in ponds with a high density of heterospecifics. Overall, our findings indicate that these multievent CR models provide a highly flexible means of modeling dispersal in dynamic landscapes

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 position of a species 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 intraspecific variation in senescence in an amphibian, Bombina variegata. We used capture–recapture data collected in four populations with contrasting life‐history strategies. Senescence trajectories were analysed using Bayesian capture–recapture models. We show that in populations with fast life histories the onset of actuarial senescence was earlier and individuals aged at a faster rate than individuals in populations with slow life histories. Our study provides one of the few empirical examples of among‐population variation in actuarial senescence patterns in the wild and confirms that the fast–slow life‐history gradient is associated with both macroevolutionary and microevolutionary patterns of actuarial senescence

Influence of lipid physical state on the in vitro digestibility of emulsified lipids

The objective of this study was to investigate the influence of the physical state of emulsified lipids on their in vitro digestibility by pancreatic lipase. A 10 wt % tripalmitin oil-in-water emulsion stabilized by sodium dodecyl sulfate (0.9 wt % SDS) was prepared at a temperature (\u3e70 °C) above the melting point of the lipid phase (Tm ≈ 60 °C). A portion of this emulsion was cooled to a temperature (0 °C for 15 min) well below the crystallization temperature of the emulsified lipid (Tc ≈ 22 °C) and then warmed to 37 °C so as to have completely solid lipid particles. Another portion of the emulsion was directly cooled from 70 to 37 °C (which is above the Tc) to have completely liquid (supercooled) lipid particles. Pancreatic lipase (8 mg/mL) and bile extract (5.0 mg/mL) were then added to each emulsion at 37 °C, and the evolution of the particle charge, particle size, appearance, and free fatty acid release were measured over a period of 2 h. It was found that the rate and extent of lipid digestion were higher in the emulsion containing liquid particles but that appreciable lipid digestion still occurred in the emulsion containing solid particles (i.e., \u3e35% lipid digestion after 2 h). These results may have important consequences for controlling the digestion rate of lipids or for developing solid lipid particle delivery systems for lipophilic functional components

Investigation of primary and secondary processes in the formation of Oxy-PAHs and Nitro-PAHs in Paris (France) by conjoining on-line and off-line measurements

The carbonaceous fraction of aerosols is composed of many compounds which constitute the organic carbon (OC) and elemental carbon (EC) components. Within the organic carbon component, Polycyclic Aromatic Hydrocarbons (PAHs) are the prevalent contributor to atmospheric pollution and emitted by incomplete combustion processes. Atmospheric oxidation of PAHs induces the formation of oxidized compounds such as oxygenated-PAHs (oxy-PAHs) and nitrated-PAHs (nitro- PAHs). The study of these PAH derivatives have become a prime concern as most are known to be carcinogenic and potentially more mutagenic than PAHs. These compounds may also instigate the formation of secondary organic aerosol (SOA), which may represent a large source of SOA in urban areas. The main objective of this study was to investigate the primary and secondary processes leading to the formation of oxy-PAHs and nitro-PAHs. This was accomplished by utilizing information obtained from intensive filter measurements along with online monitoring. To the best of our knowledge, this unique approach has not been explored yet. Measurements were conducted at SIRTA-LSCE, which features, the suburban background conditions of Paris, France. Results highlight high concentrations of oxy-PAHs and nitro-PAHs during the period 14-21, March 2015, including specific secondary PAH derivatives as 6H-dibenz[b,d]pyran-6-one, acenaphthenequinone and 2-nitrofluoranthene. This suggests that such species could be generated through secondary processes related to high NO3 - and SO4 2- concentrations that can be explicitly observed considering ACSM results. Besides, the formation of 6H-dibenz[b,d]pyran-6-one seems to be highly influenced by the daytime chemistry while 2-nitrofluoranthene may be generated during nighttime (potentially involving NO3 radical chemistry). Interestingly, fossil-fuel-based Black Carbon (BCff) and 1-nitropyrene (1-NP, a promising marker for diesel emissions) present similar temporal concentration profiles. Discussion will further accentuate diurnal variations, information about the day- and nighttime chemistry, and also usefulness of combining off-line and on-line measurements to ensure a comprehensive understanding of the prevalent atmospheric processes

To breed or not to breed: past reproductive status and environmental cues drive current breeding decisions in a long‐lived amphibian

International audienceIteroparity is an adaptive response to uncer- tainty in reproductive success. However, spreading repro- ductive success over multiple reproduction events during a lifetime is constrained by adult mortality and the stochas- ticity associated with interactions between external factors and physiological states. The acquisition of information about environmental conditions during the growth of prog- eny and sufficient resources during the non-reproductive period are key factors for breeding success. Consequently, we hypothesized that long-lived animals may skip a breed- ing opportunity when information about unfavourable environmental conditions is available. In addition, nutri- tional constraints could prevent an animal from replenish- ing its reserves sufficiently to invest in the current breeding period. We investigated these questions using capture– recapture data from a 5-year study on a large population of yellow-bellied toads in a forest in north-eastern France. We took advantage of various advances in multi-state cap- ture–recapture models (e.g. unobservable states and mix- ture models) to test our hypotheses. Our results show that the combined effects of rainfall deficit and the breeding/ non-breeding state of individuals during the past breeding season affect breeding probability during the following breeding opportunity. We also found that females breed less frequently than males, suggesting that the overall energy cost of reproduction differs between genders. Finally, the results indicate that toad survival appears to be negatively influenced by rainfall deficits. We discuss the yellow-bel- lied toad’s reproductive behaviour in term of bet-hedging strategy and life history trait evolution

Secondary organic carbon (SOC) estimation using several indirect techniques and the evaluation of their uncertainties

Knowledge of the relative contribution of primary and secondary organic aerosol fractions is important in formulating effective control measurements for ambient particulate matter (PM), and the main part of Organic Aerosol (OA) in urban and rural atmospheres is found to be of secondary origin. However, its exact contribution still remains uncertain despite intensive efforts undertaken during the last decades to characterize and understand the chemistry leading to Secondary Organic Aerosol (SOA). Indeed, there is still no direct way to separate secondary to primary organic aerosol fractions. Quantification of Secondary Organic Carbon (SOC) is furthermore difficult because of our limited understanding of the molecular composition of SOC and because of the presence of a large, but unknown, number of secondary organic products. This study has been purposely carried out to estimate the contribution of SOC fraction to OA content, by using various semi-direct and indirect methodologies and evaluate associated uncertainties involved in the following outcomes. Measurements were conducted at SIRTA-LSCE, a well arranged atmospheric site in the vicinity of Paris (France), over a period from 6 to 24 March 2015. This was accomplished by utilizing information obtained from intensive filter measurements conducted at every 4 hours. SOC estimations were proposed using Positive Matrix Factorization applied to Aerosol Chemical Speciation Monitor (ACSM) measurements as well as using off-line data analyses, such as EC-, WSOC-, and SOA tracer-based methods. Results might also assert the photochemical origin of SOA, although the relative contribution to the OC and the SOA formation may differ during the chosen period. Large discrepancies were accounted for in the SOC estimations furnished using different techniques. Results imply that cautions should be taken while estimating SOC. Discussion will lead to profound information about the limitations and challenges associated to SOC estimations using different techniques

A synergic approach to perform source apportionment of organic aerosol using offline and online measurements in Positive Matrix Factorization

Understanding the sources and processes responsible of atmospheric PM composition and concentration is required to implement effective PM control strategies. During the last decade, the use of online non-refractory submicron aerosol mass spectrometer (AMS) and aerosol chemical speciation monitor (ACSM) measurements have successfully allowed real time measurements of organic fraction. However, to profoundly understand the sources and formation processes of organic aerosol, a comprehensive source apportionment analysis is still needed. The combination of different datasets from several measurements to refine the apportionment of OA sources, and notably secondary ones, is probably one of the best way to achieve this goal. To the best of our knowledge, this has never been performed extensively (Crippa et al. 2013; Huang et al. 2014; McGuire et al. 2014; Petit et al. 2014; Sun et al. 2012). In the present study, we propose a novel approach of combining online and offline measurements in statistical source-receptor model such as Positive matrix factorization (PMF). An intensive campaign was performed at the SIRTA atmospheric research observatory, representing the suburban background air quality conditions of the Paris area (about 25 km SW from Paris city center). PM10 samples were collected every 4 hours over a period of intensive PM pollution events (PM > 50 μg m-3 over several days) on March 6- 24 2015, concomitantly with online measurements, carried out using ACSM, 7Aethalometer, TEOMFDMS, NOx and O3 analyzers. Regular PMF was first performed on organic matrix obtained from offline measurements. Figure 1 shows the eight different factors obtained using the specific primary (i.e. levoglucosan (biomass burning), methane sulphonic acid (MSA) (marine), 1-nitropyrene (traffic)) and secondary organic molecular markers (i.e. hydroxyglutaric acid (α-pinene), 3-methyl,5- nitrocatechol (biomass burning), α-methyl glyceric acid (isoprene)). PMF was also performed on ACSM OA matrix and has been deconvolved into four factors including HOA, BBOA1, BBOA2 and OOA (Figure 1). These results show that PMF performed on individual dataset is not truly viable to procure complete information about the different atmospheric processes. Lack of high-resolution time to understand rapid atmospheric processes in case of filter measurements, and lack of specific markers to validate oxygenated factors while using online measurements, have emerged out as a critical limitation of regular PMF. Here, the synergic approach proposes to combine traditional off-line PMF factors, such as primary biomass burning, primary biogenic, secondary biogenic, traffic, with OA matrix from ACSM measurements. The unified matrix was again deconvolved with PMF in order to retrieve factors such as HOA, BBOA, OOA, and to explore additional information about OA sources. Discussion will further focus on the factors obtained by combining online and offline measurements in PMF, and their benefits over the conventional approach