Species responses to climate change and landscape fragmentation: the central role of dispersal

Le changement climatique actuel entraine l'extinction de populations ainsi que des changements dans leur aire de répartition et leur composition. La dispersion impacte ces deux dernières réponses puisqu'elle permet de coloniser de nouveaux habitats et influence la composition des populations au travers du flux de gènes. En fonction de son adaptativité, la dispersion peut promouvoir ou réduire l'adaptation locale et modifier l'importance relative de la plasticité phénotypique et de l'adaptation génétique dans le changement de composition phénotypique des populations. Cependant, la fragmentation du paysage entrave la dispersion, affectant les deux réponses des populations au réchauffement et modifiant l'influence relative des différents processus impliqués dans ces réponses. Le but de cette thèse était de comprendre comment les réponses des populations au changement climatique pouvaient être affectées par la fragmentation du paysage et la dispersion. En suivant des populations de lézards distribuées dans un système expérimental permettant de manipuler simultanément les conditions climatiques et la connectivité entre habitats, nous avons démontré que la connectivité réduisait les effets du réchauffement sur la dynamique et la composition des populations. Nous avons observé que les décisions de dispersion étaient influencées par des facteurs intrinsèques et extrinsèques permettant de réduire l'influence d'un climat plus chaud sur la dynamique des populations, mais en réduisant également la densité des populations en climat plus froid. Etonnamment, nous avons aussi trouvé que la dispersion pouvait modifier la force et la direction des pressions de sélections agissant sur les phénotypes. Les actions conjointes de la dispersion et de la sélection contrebalançaient ainsi la réponse plastique des individus. En les intégrant dans un modèle, des décisions de dispersion adaptative similaires avaient une forte influence sur la persistance prédite des espèces face au réchauffement. En effet, nous avons démontré que la dispersion adaptative favorisait le changement d'aire de répartition des populations et réduisait leur risque d'extinction, en comparaison à un modèle avec dispersion aléatoire (indépendante de facteurs intrinsèques et extrinsèques). Plutôt que de considérer la dispersion comme un processus neutre, nos résultats soulignent l'importance de la considérer comme un mécanisme complexe, façonné par de multiples facteurs et capable de déterminer les réponses des espèces au changement climatique. Nos résultats suggèrent que la fragmentation pourrait fortement augmenter l'influence du changement climatique sur les populations et précipiter leur extinction. Nous appelons donc à une meilleure intégration de la dispersion et de la structure du paysage dans les études sur les réponses des populations au changement climatique.Contemporary climate change is leading to population extinction, range shift and composition changes. Dispersal shapes these two last responses by allowing colonization of new habitats and by affecting population composition through gene flow. Depending on its adaptiveness, dispersal can promote or hinder local adaptation and modify the relative influence of phenotypic plasticity and evolutionary adaptation in population phenotypic change. However, landscape fragmentation hampers dispersal, affecting both population responses to climate change, and modifying the relative influence of the different processes involved in these responses. The aim of this PhD was to understand how population responses to climate change could be influenced by landscape fragmentation and by dispersal. By monitoring lizards inhabiting experimental populations where both climatic conditions and connectivity among them were manipulated, we demonstrated that connectivity among populations buffered climate change effects on population dynamics and phenotypic composition. We found that dispersal decisions depended on multiple intrinsic and extrinsic factors allowing to reduce the influence of warmer climate on population dynamics, but decreasing population density in cooler climate. Surprisingly, we also found that dispersal could modify the strength and direction of climate-dependent selection pressures on phenotypes. As a consequence, selection and dispersal acted in synergy to counteract the plastic response of the individuals. When integrated into a model, similar adaptive dispersal behavior strongly altered predictions of species persistence under climate change. We indeed found that adaptive dispersal promoted species range shift and reduced extinction probability compared to a model where dispersal was random (i.e.independent of intrinsic and extrinsic factors). Rather than considering dispersal as a neutral process, our results highlighted the importance to consider it as a complex mechanism shaped by multiple factors and able to drive population responses to climate change. Our results further suggest that fragmentation could strongly increase the influence of climate change on populations and may therefore precipitate their extinction. We thus call for a better integration of dispersal and landscape structure when studying population responses to climate change

Optimally Scheduling Public Safety Power Shutoffs

In an effort to reduce power system-caused wildfires, utilities carry out public safety power shutoffs (PSPS) in which portions of the grid are de-energized to mitigate the risk of ignition. The decision to call a PSPS must balance reducing ignition risks and the negative impact of service interruptions. In this work, we consider three PSPS scheduling scenarios, which we model as dynamic programs. In the first two scenarios, we assume that N PSPSs are budgeted as part of the investment strategy. In the first scenario, a penalty is incurred for each PSPS declared past the Nth event. In the second, we assume that some costs can be recovered if the number of PSPSs is below $N$ while still being subject to a penalty if above N. In the third, the system operator wants to minimize the number of PSPS such that the total expected cost is below a threshold. We provide optimal or asymptotically optimal policies for each case, the first two of which have closed-form expressions. Lastly, we establish the applicability of the first PSPS model's policy to critical-peak pricing, and obtain an optimal scheduling policy to reduce the peak demand based on weather observations

Impact of Zika Virus Emergence in French Guiana: A Large General Population Seroprevalence Survey.

BACKGROUND: Since the identification of Zika virus (ZIKV) in Brazil in May 2015, the virus has spread throughout the Americas. However, ZIKV burden in the general population in affected countries remains unknown. METHODS: We conducted a general population survey in the different communities of French Guiana through individual interviews and serologic survey during June-October 2017. All serum samples were tested for anti-ZIKV immunoglobulin G antibodies using a recombinant antigen-based SGERPAxMap microsphere immunoassay, and some of them were further evaluated through anti-ZIKV microneutralization tests. RESULTS: The overall seroprevalence was estimated at 23.3% (95% confidence interval [CI], 20.9%-25.9%) among 2697 participants, varying from 0% to 45.6% according to municipalities. ZIKV circulated in a large majority of French Guiana but not in the most isolated forest areas. The proportion of reported symptomatic Zika infection was estimated at 25.5% (95% CI, 20.3%-31.4%) in individuals who tested positive for ZIKV. CONCLUSIONS: This study described a large-scale representative ZIKV seroprevalence study in South America from the recent 2015-2016 Zika epidemic. Our findings reveal that the majority of the population remains susceptible to ZIKV, which could potentially allow future reintroductions of the virus

Spatial Distribution and Burden of Emerging Arboviruses in French Guiana.

Despite the health, social and economic impact of arboviruses in French Guiana, very little is known about the extent to which infection burden is shared between individuals. We conducted a large multiplexed serological survey among 2697 individuals from June to October 2017. All serum samples were tested for IgG antibodies against DENV, CHIKV, ZIKV and MAYV using a recombinant antigen-based microsphere immunoassay with a subset further evaluated through anti-ZIKV microneutralization tests. The overall DENV seroprevalence was estimated at 73.1% (70.6-75.4) in the whole territory with estimations by serotype at 68.9% for DENV-1, 38.8% for DENV-2, 42.3% for DENV-3, and 56.1% for DENV-4. The overall seroprevalence of CHIKV, ZIKV and MAYV antibodies was 20.3% (17.7-23.1), 23.3% (20.9-25.9) and 3.3% (2.7-4.1), respectively. We provide a consistent overview of the burden of emerging arboviruses in French Guiana, with useful findings for risk mapping, future prevention and control programs. The majority of the population remains susceptible to CHIKV and ZIKV, which could potentially facilitate the risk of further re-emergences. Our results underscore the need to strengthen MAYV surveillance in order to rapidly detect any substantial changes in MAYV circulation patterns

Heat-Inactivation of Fetal and Newborn Sera Did Not Impair the Expansion and Scaffold Engineering Potentials of Fibroblasts

Heat inactivation of bovine sera is routinely performed in cell culture laboratories. Nevertheless, it remains debatable whether it is still necessary due to the improvement of the production process of bovine sera. Do the benefits balance the loss of many proteins, such as hormones and growth factors, that are very useful for cell culture? This is even truer in the case of tissue engineering, the processes of which is often very demanding. This balance is examined here, from nine populations of fibroblasts originating from three different organs, by comparing the capacity of adhesion and proliferation of cells, their metabolism, and the capacity to produce the stroma; their histological appearance, thickness, and mechanical properties were also evaluated. Overall, serum inactivation does not appear to provide a significant benefit

Glucuronidated Metabolites of Bisphenols A and S Alter the Properties of Normal Urothelial and Bladder Cancer Cells

Bisphenol A (BPA) and bisphenol S (BPS) are synthetic chemicals used to produce plastics which can be released in food and water. Once ingested, BPA and BPS are metabolized by the liver, mainly as glucuronidated metabolites, and are excreted through urine. Since urine can be stored for many hours, the bladder is chronically exposed to BP metabolites, and studies have shown that these metabolites can remain active in the organism. Therefore, the effect of physiological concentrations of glucuronidated BPs was evaluated on the bioenergetics (glycolysis and mitochondrial respiration), migration and proliferation of normal urothelial cells, and non-invasive and invasive bladder cancer cells. The results demonstrated that an exposure of 72 h to glucuronidated BPA or BPS decreased the bioenergetics and activity of normal urothelial cells, while increasing these parameters for bladder cancer cells. These findings suggest that BP metabolites are not as inactive as initially believed, and their ubiquitous presence in the urine could promote bladder cancer progression

Data from: Matching habitat choice promotes species persistence under climate change

Species may survive under contemporary climate change by either shifting their range or adapting locally to the warmer conditions. Theoretical and empirical studies recently underlined that dispersal, the central mechanism behind these responses, may depend on the match between an individuals’ phenotype and local environment. Such matching habitat choice is expected to induce an adaptive gene flow, but it now remains to be studied whether this local process could promote species’ responses to climate change. Here, we investigate this by developing an individual-based model including either random dispersal or temperature-dependent matching habitat choice. We monitored population composition and distribution through space and time under climate change. Relative to random dispersal, matching habitat choice induced an adaptive gene flow that lessened spatial range loss during climate warming by improving populations' viability within the range (i.e. limiting range fragmentation) and by facilitating colonization of new habitats at the cold margin. The model even predicted in some cases range contraction under random dispersal but range expansion under optimal matching habitat choice. These benefits of matching habitat choice for population persistence mostly resulted from adaptive immigration decision and were greater for populations with larger dispersal distance and higher emigration probability. We also found that environmental stochasticity resulted in suboptimal matching habitat choice, decreasing the benefits of this dispersal mode under climate change. However population persistence was still better under suboptimal matching habitat choice than under random dispersal. Our results highlight the urgent need to implement more realistic mechanisms of dispersal such as matching habitat choice into models predicting the impacts of ongoing climate change on biodiversity

Biogeographic drivers of community assembly on oceanic islands: The importance of archipelago structure and history

International audienceAim: Accounting for geo-environmental dynamics is crucial to understand community assembly across islands. Whittaker et al. (J Biogeogr, 35:977–994, 2008)’s General Dynamic Model (GDM) aims towards this goal. Yet, it does not explicitly consider that most islands belong to archipelagos. We examined how island biodiversity dynamics are influenced by the interaction of eco-evolutionary processes acting at the archipelago level with each island's geo-environmental dynamics.Location: Hypothetical archipelagos.Taxon: Any.Methods: We used an individual-based model, ecologically neutral within the archipelago. Several islands emerge in succession with a typical volcanic ontogeny. We considered both mainland and inter-island dispersal. Geographically isolated lineages diverged over time, possibly speciating.Results: We found diversity to be at dynamic equilibrium. In an archipelago, islands hosted more diversity and more endemic species, at both island and archipelago levels, than an equivalently-sized single isolated island. This was due to an ‘archipelago effect’: inter-island dispersal increased within-island diversity through species occurrence on multiple islands; species may undergo anagenetic changes on the colonised islands, eventually speciating, thereby increasing archipelago diversity. Biodiversity dynamics of different islands may differ even on islands with identical geo-environmental dynamics because the archipelago effect varied over time and affected each island differently (‘history effect’). By accounting for these effects, we predicted detectable deviations from the GDM predictions, which are largest for remote archipelagos, with islands located close together and with an intermediate time of island emergence. In linear stepping-stone archipelagos, we predicted higher diversity on centrally located islands.Main conclusions: Our results demonstrate that analyses of insular biodiversity data would greatly benefit from explicitly accounting for both archipelago and history effects. We suggest incorporating variables characterising the spatio-temporal structure of the whole archipelago. We discuss possible difficulties in distinguishing between the archipelago effect and equilibrium diversity dynamics

Importance de la connectivité du paysage pour évaluer l’impact du réchauffement climatique sur les tritons

peer reviewedContexte Dans le contexte du réchauffement climatique, la fragmentation du paysage peut à la fois impacter la dispersion des espèces vers des microclimats servant de zone refuge, mais aussi mener à des modifications dans la composition phénotypique des populations. Méthode Nous avons utilisé une approche expérimentale en milieu semi-naturel pour évaluer si l’effet d’une augmentation de 2°C sur l’abondance et la réponse phénotypique de populations de tritons palmés est influencé par la connectivité entre microclimats. Résultats Un climat plus chaud impacte négativement l’abondance des tritons adultes, altère la composition phénotypique des populations et influence la décision d’émigration des juvéniles. Cependant la connectivité entre les habitats thermiques annule ou inverse ces effets. Conclusion La conservation de zones microclimatiques et le maintien de la connectivité paysagère devraient être une préoccupation majeure pour réduire l’impact du réchauffement climatique sur les amphibiens