HAL Université des Antilles
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Tracking the urban spread of Usutu virus in southern France: detection across biological and environmental matrices
No full textInternational audienceThe Usutu virus, a neurotropic Orthoflavivirus transmitted by mosquitoes, was first identified in South Africa in 1959 and has progressively spread across Europe over the past two decades. This virus follows an enzootic cycle between mosquitoes and birds, leading to periodic outbreaks that have caused significant bird mortality. Although primarily an avian pathogen, Usutu virus can occasionally infect humans and other mammals who act as incidental or dead-end hosts. The repeated avian epizootics observed in Europe in the last two decades raise concerns about potential zoonotic risks, even though human infections remain rare. In most cases, human infection is either asymptomatic or results in mild symptoms. However, in some instances, Usutu virus has been linked to severe neurological conditions, including encephalitis and meningoencephalitis. The Occitanie region in the south of France is particularly vulnerable to this threat due to its ecosystem, which harbors both competent mosquito vectors and numerous avian hosts that act as amplifying hosts for the virus. We investigated the urban circulation of Usutu virus in the city of Montpellier, where the first human case of infection by this virus in France was previously identified. To assess the presence of Usutu virus, we conducted a repeated cross-sectional study using serological (ELISA, microneutralization) and molecular (RT-qPCR) analyses of captive avifauna, including a longitudinal study of captive birds at the Montpellier zoological park between 2016 and 2024. Additionally, in 2024, we completed our study with avian cloacal swabs, pigeon droppings, rat blood, mosquito faeces, and environmental water samples (dPCR). Our findings revealed active circulation of the Usutu virus in the urban environment over multiple years. Furthermore, we demonstrated the feasibility of detecting the virus in droppings and environmental waters, highlighting the potential of environmental surveillance as a non-invasive and largescale method. This study contributes to a better understanding of Usutu virus circulation and highlights its established presence in urban areas
ECOLOGGING : réseau de Stations Instrumentées Évolutives Modulables et Déplaçable en IoT
No full textInternational audienceCe poster qui est présenté aux J2M 2025, montre le réseau de stations instrumentées IoT low cost développées dans le cadre du projet ECOLOGGING pouvant réaliser des mesures de météorologie, de température et de niveau d'eau, de suivi du sol (en humidité et température) et de Gaz à Effet de Serre.Ces stations ont été déployées sur le territoire français, ainsi qu'en Guyane afin de les tester dans différents écosystèmes et conditions climatiques.Nous présentons également toute la chaîne d'acquisition sécurisée qui utilise un broker MQTTs, Node-Red, une base de données et Grafana.L'émission et la réception des données en 4G est fiable tout comme la récupération des données de l’ensemble des stations qui ont été déployées sur les différents sites, y compris en Guyane
Ant–plant relationships in an Amazonian rainforest understory: A network approach
No full textInternational audience1. Although tropical rainforest ants are abundant and have high species richness, with their community structure well known at the canopy and ground levels, the understory is frequently neglected. 2. To fill this gap, we looked for ants nesting in this stratum in an Amazonian rainforest and noted the occurrence of colonies in the debris accumulated between the fronds of the palm tree Astrocaryum sciophilum or associated with eight myrmecophytes (i.e., plants that shelter ant colonies in hollow structures called domatia).3. We analysed these plant-ant relationships by conducting a network approach looking for the degree of specialisation between partners (specialisation index), the differences in intensity between links (weighted nestedness) and the proportion of realised interactions relative to the number of potential interactions (connectance), including ground-and canopy-nesting ants.4. This results in a highly modular pattern of interactions with one module per plant species based on the 98 ant species recorded. We showed the importance of ground-nesting species for Astrocaryum, although 40.5% of them sheltered a colony of the arboreal Odontomachus hastatus. Among myrmecophytes, a strong specificity was noted for Hirtella physophora (Chrysobalanaceae) and Maieta guianensis (Melastomataceae) that sheltered at more than 90% Allomerus decemarticulatus and Pheidole minutula, respectively. Cordia nodosa (Boraginaceae) has an intermediary value (45.3% associated with Allomerus octoarticulatus), whereas Cecropia obtusa (Urticaceae), Duroia longiflora (Rubiaceae), Tachigali paniculata (Fabaceae) and Tococa guianensis (Melastomataceae) can shelter several ant species belonging mostly to a single genus. Tachia guianensis, considered a 'non-specialised' myrmecophyte, shelters species from different genera.</p
Nutrient addition to a white sand tropical forest results in greater growth of saplings of canopy tree species than understorey specialist tree species
No full textInternational audienceIn tropical rain forest understories, canopy tree saplings coexist with understorey specialist trees, in a highly competitive environment for light, space, and soil nutrients. To investigate the impact of increasing nutrient pollution from human activity, we assessed differences between canopy trees saplings and understory specialists in their crown structures, allometries, and growth rates in response to experimental nutrient fertilization. In a nutrient-poor white sand forest in Sabah, Malaysian Borneo we measured tree size and crown dimensions for understorey specialists and canopy tree saplings (≤ 10 cm diameter) before and after experimental fertilization with nitrogen and calcium carbonate. Results showed that saplings of canopy species were taller than understorey specialists for a given stem diameter, but crown allometries were similar. Three years of fertilization did not affect allometric relationships between diameter and tree height or crown dimensions, suggesting that these allometries are stable and resource-independent. However, relative crown radius growth rate and crown volume growth rate for canopy tree saplings were three times faster after N + CaCO3 fertilization when compared to controls, demonstrating canopy tree saplings' crown plasticity to maximize access to light. This study highlights different strategies employed by canopy and understorey species in the competitive forest understorey. Canopy saplings showed greater crown plasticity, investing added soil nutrients into crown expansion for enhanced light interception. Nitrogen deposition could thus advantage canopy species through increased competition with understory specialists resulting in potential species loss. The stability of the allometric relationships, when forests are subjected to nitrogen deposition supports their use for biomass estimation
<i>Pheidole megacephala</i>: An invasive ant that raids colonies of the red imported fire ant, <i>Solenopsis invicta</i>
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The role of cretaceous tectonics in the present-day architecture of the NICE arc (Western Subalpine foreland, France)
No full textInternational audienceThe Nice arc architecture, located at the southern tip of the Western Alps, is very singular, with a strong and narrow curvature. This particular shape could be the result of inherited structures that guide subsequent deformations during compressional events, as has been demonstrated in other parts of the belt. To achieve this objective, we adopted a multidisciplinary approach to characterize the geometry, kinematics, and timing of deformations associated with the various tectonic episodes that structured the arc. A special focus on the Cretaceous formations has revealed that the Cenomanian deposits show significant thickness variations and strong disturbances associated with fault activity. At this time, the formation of narrow, elongated basins was controlled by a system of NNE-SSW trending left-lateral strike-slip faults associated with NW-SE trending normal strike-slip faults and normal faults, dated at 81 ± 13 Ma on calcite recrystallised on the fault planes. During the Cenozoic, two phases of shortening reactivated the faults bounding these basins. An Oligocene phase corresponds to a NE-SW compression, expressed by NW-SE trending folds and thrust and reactivation of first phase faults, dated at 28.7 ± 6.1 Ma, 28.8 ± 8.4 Ma and 27.3 ± 6.3 Ma. The Mio-Pliocene phase is characterised by N-S compression with E-W folds that interfere with the Oligocene folds and reactivate the earlier faults. A Lower Miocene age of 18.2 ± 1.1 Ma and a Pliocene age of 3.16 ± 0.47 Ma pinpoint the timing of these last deformation phase
Back to the Source: Connecting the Seismological Observations of Le Teil Earthquake (M w 4.9, 2019/11/11, France) to the Local Geology
No full textInternational audienceAbstract The spatial distribution of seismicity in active fault zones depends primarily on the geometry of the fault networks. However, recent advances suggest that seismic activity may also be controlled by the rheology of the geological units surrounding fault zones. In the present work, we use seismological and geological analyses to investigate the influence of the local geology on the rupture nucleation and propagation of the 2019 Le Teil earthquake (France; M L = 5.4; M w = 4.9) and on the distribution of its aftershocks. The kinematic rupture model of the mainshock, obtained by joint inversion of seismological and INSAR data, shows that the rupture nucleated at 1 km depth and propagated mainly up‐dip and bilaterally. Template matching detection identifies 115 aftershocks (−1.6 ≤ M L ≤ 2.5) in the two months following the mainshock. Double difference location shows that the aftershocks delineate a 4 km‐long NE‐SW plane with a 60° dip to the SE, consistent with the extent and the geometry of the La Rouvière fault activated during the mainshock. By placing the seismicity in the local geological context, we conclude that the seismic activity was largely controlled by the rheological properties of the contrasting lithology. The mainshock nucleated in marly‐limestone, but the coseismic slip was maximum above 0.6 km depth in a massive limestone more prompt to store elastic strain. The aftershocks occurred mainly in marls and marly limestone. They are interpreted as ruptures in competent beds of limestones of varying thickness, interbedded with marls
