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Antestiopsis thunbergii is the most important coffee pest in Burundi causing yield losses of up to 30%. The aim of this study was to estimate its occurrence and density and to assess the species diversity of native egg-parasitoids associated to this pest in coffee agroecosystems. Our study was carried out in four coffee growing agro-ecological zones of Burundi namely; the humid west escarpments, the humid central highlands, the sub-humid central highlands and the sub-humid southeastern and northern depressions. In total, 600 coffee trees, randomly selected in 40 coffee plots of 20 communes were investigated at three phenological stages of the crop viz. October 2019 (coffee was flowering), January 2020 (coffee berries were immature green) and April 2020 (coffee berries were mature green and red). The results showed a permanent presence of A. thunbergii with an increasing occurrence and density with time. Densities were above the economic threshold (one antestia bug per tree), except in the humid west escarpments. Differences were highly significant among the four agro-ecological zones at each time of sampling. The humid central highlands zone registered the highest densities with 1.55, 1.31 and 2.67 antestia bugs per tree in October, January and April, respectively. The humid west escarpments zone recorded lower densities of 0.38, 0.44 and 0.88 antestia bugs per tree, for the same periods respectively. From the 4,776 eggs collected from the field, 1,99 egg-parasitoids of A. thunbergii were obtained and identified, namely Trissolcus sp. (59.2%), Telenomus seychellensis (29.6%), Gryon fulviventre (2.9%), Anastatus sp. (8.1%) and Acroclisoides africanus (0.2%).

International audience; Key message Decreasing stand density increases resistance, resilience, and recovery ofQuercus petraeatrees to severe drought (2003), particularly on dry sites, and the effect was independent of tree social status. Context Controlling competition is an advocated strategy to modulate the response of trees to predicted changes in climate. Aims We investigated the effects of stand density (low, medium, high; relative density index 0.20, 0.53, 1.04), social status (dominant, codominant, suppressed), and water balance (dry, mesic, wet; summer water balance - 182, - 126, - 96 mm) on the climate-growth relationships (1997-2012) and resistance (Rt), resilience (Rs), and recovery (Rc) following the 2003 drought. Methods Basal area increments were collected by coring (269 trees) in young stands (28 +/- 7.5 years in 2012) of sessile oak (Quercus petraea) in a French permanent network of silvicultural plots. Results We showed that the climate-growth relationships depend on average site-level water balance with trees highly dependent on spring and summer droughts on dry and mesic sites and not at all on wet sites. Neither stand density nor social status modulated mean response to climate. Decreasing stand density increased Rt, Rs, and Rc particularly on dry sites. The effect was independent of tree social position within the stand. Conclusion Reducing stand density mitigates more the effect of extreme drought events on drier sites than on wet sites.

Le criquet pèlerin, Schistocerca gregaria Forskål, 1775, est un ravageur majeur pour l'agriculture. Affiner les connaissances sur sa distribution spatiale est essentiel pour sa gestion préventive. Dans ce but, nous avons utilisé au Tchad une technique de lissage spatial de densités sur 7014 observations du criquet pèlerin (1965-1971 et 1986-2017) afin d'élaborer des cartes saisonnières de répartition pour les périodes d'invasion et de rémission. Trois zones correspondant à des aires de reproduction et foyers de grégarisation ont été identifiées : (1) Kanem/lac Tchad, (2) Batha, (3) Ennedi. La première pourrait être un nouveau foyer de grégarisation. Ces zones se rajoutent à celle du massif du Tibesti, où les signalements sont plus rares que par le passé à cause de l'insécurité. Des prospections plus régulières devraient permettre de confirmer que la distribution du criquet pèlerin a récemment évolué. Mots clés : Schistocerca gregaria / reproduction / prévention des risques / distribution spatiale / plasticité phénotypique Abstract-Mapping of the breeding and gregarization areas of the desert locust in Chad. The desert locust, Schistocerca gregaria Forskål, 1775, is a major threat to agriculture. Refining our knowledge on its spatial distribution is a key point for its preventive management. To do so, we used in Chad a method of spatial smoothing of densities upon 7014 survey points (1965-1971 and 1986-2017) of the desert locust to develop seasonal distribution maps for invasion and remission periods. Three zones corresponding to breeding and gregarization areas have been identified: (1) Kanem/lake Chad, (2) Batha, (3) Ennedi. The first one may be a new gregarization area. These zones add to the Tibesti mountains where locust reports are less frequent than in the past, due to insecurity. More regular surveys should confirm that the distribution of the desert locust has recently changed.

International audience; Hydroacoustics has become a requisite method to assess fish populations and allows to describe the relationships of fish with other elements of the aquatic ecosystem. This nonintrusive method is currently an integral part of the sampling procedures recommended for fish stock assessment by the Water Framework Directive and has been standardized by the European Committee for Standardization [CEN (2014) CSN EN 15910 - Water quality - Guidance on the estimation of fish abundance with mobile hydroacoustic methods, Category: 7577 Water quality. Biological.]. In Europe, hydroacoustic surveys are performed in freshwater using different frequencies. Consequently, there is a need to evaluate if survey results can be compared. This study aimed to carry out in situ comparisons at the 38 kHz frequency (noted f) with two other commonly used frequencies, 70 and 200 kHz. The 38 kHz frequency has seldom been compared with other frequencies in freshwater although it is widely used worldwide, especially in the Great Lakes of North America and in Sweden. In 2016, hydroacoustic data were acquired in Lakes Annecy and Bourget using methods validated in previous studies that compared the frequencies 70, 120 and 200 kHz. This study showed similar density and biomass estimations as a function of frequency, density(f) and biomass(f), between the frequencies studied for low to moderate fish densities. For higher fish densities, the results were more variable and need to be verified. Fish density(f) and biomass(f) estimations sometimes exhibit differences between frequencies, which is not fully in agreement with theoretical calculations. The aim of this study was to evaluate frequency comparisons in practise. However, if the differences on acoustic metrics, density(f) or biomass(f) between frequencies were occasionally statistically significant, the differences were small enough to be considered negligible for fish population management. These analyses led to better knowledge of the responses from fish in temperate lakes for the studied frequencies. Our findings should be considered when revising the CEN standard.

L’espace CEDEAO subit de profondes mutations spatiales liées à une forte croissance démographique, au changement climatique et à une croissance économique exceptionnelle. Entre 1950 et 2015, cet espace a accueilli 280 millions nouveaux habitants, soit une moyenne de 4,3 millions nouveaux arrivants par an, parmi lesquels 2,4 millions nouveaux urbains et 1,9 millions nouveaux ruraux. Les dynamiques de peuplements impulsées par ces forces démographiques, climatiques et économiques, s’effectuent parfois en direction des terres neuves parmi lesquelles les espaces protégés. Ces derniers constituent des réserves de biodiversité qui hébergent des réservoirs de pathogènes et d’insectes vecteurs. L’homme, en exploitant ces nouveaux territoires, s’exposent donc à la piqûre d’insectes vecteurs de maladies ou au contact d’animaux réservoirs de pathogènes, tel que le virus Ebola. Par la densification de sa présence et son extension spatiale généralisée, l’homme créé également de plus en plus de promiscuité avec les animaux sauvages. Dans l’espace CEDEAO, les chimpanzés et quelques espèces de chauve-souris semblent représenter le plus grand danger pour l’homme au regard du risque de transmission du virus Ebola. Cette étude replace l’épidémie d’Ebola survenue en 2013 en Guinée dans son contexte historique et panafricain. Puis, elle présente brièvement le rôle connu de la faune sauvage dans l’épidémiologie d’Ebola et de quelles manières les changements environnementaux opèrent sur les principaux réservoirs connus de ce virus. Ensuite, elle retrace les grandes lignes de l’évolution spatio-temporelle de l’épidémie d’Ebola survenue dans l’espace CEDEAO, en tentant de faire apparaître les tenants et les aboutissants géographiques de cette catastrophe épidémiologique. ECOWAS space undergoes deep modifications related to population growth, climate change and economic development. Between 1950 and 2015, this space accommodated 280 million new inhabitants, i.e. an average of 4.3 million new arrivals a year, among which 2.4 million new urban and 1.9 million new rural. The dynamics of settlements caused by these demographic, climatic and economic phenomena are most of the time carried out towards free lands, among which protected areas. The latter constitutes reserves of biodiversity but also a reservoir of pathogens and of insect vectors. Man, by exploiting these new territories, thus expose himself to the bite of an insect vectors of disease or to a contact with an animal reservoir of a pathogen, such as the Ebola virus. By the thickening of its presence and its generalized space extension, man also created more and more promiscuity with wild animals. In ECOWAS space, chimpanzees and some species of bats seem to represent the greatest danger to man taking into consideration transmission risk of the Ebola virus. This study sets the epidemic of Ebola that occurred in 2013 in Guinea into its historical and Panafrican context. Then, it briefly presents the acknowledged role of wildlife in the epidemiology of Ebola and in which ways the environmental changes operate on the known reservoir of this virus. At last, it reminds of the broad outlines of the space-time evolution of the epidemic of Ebola which occurred in ECOWAS space, while trying to reveal the geographical ins and outs of this epidemiological catastrophe.

Fruit flies (Diptera: Tephritidae) are considered to be major pests of mango (Mangifera indica) worldwide. Their management, with an increasing focus on replacing synthetic pesticides with alternative pest control methods, is a challenging issue. A study was carried out from 2015 to 2017 in Reunion Island under field conditions in order to characterize the incidence of fruit flies on mango production and to link fruit fly infestation with fruit maturity and fly pressure. Mango fruits were mainly infested by Bactrocera zonata. Few fruits were infested by Ceratitis quilicii, and even fewer by Ceratitis capitata. Infestation increased as fruits ripened. Less than 4% of the fruits were infested at the green, green-mature and early yellow-point stages. Infestation increased to 10–11% at later yellow-point stages, and reached 14–16% at ripe and overripe stages. Fruit infestation was closely related to changes in the peel texture (firmness, in particular) and chlorophyll fluorescence of the fruit as it ripened. Whereas variability in fruit fly abundance in traps was observed between orchards and years, it did not clearly explain variability in fruit infestations, which was mostly explained by variability in fruit maturity. The study suggests that fruit fly trapping is not adequate to assess infestation risk or to guide management decisions, but instead provides evidence that fruit fly damage could be reduced by adjusting harvest timing, especially by harvesting fruits at the green-mature stage or at the yellow-point onset.

International audience; Le nouvel horizon sénégalais. Peuplement et urbanisation des campagnes occidentales aux périphéries orientales Résumé Alors que le peuplement du territoire sénégalais se concentrait dans quelques parties du pays, plusieurs processus contemporains remettent en question la répartition spatiale de la population : la densification de zones auparavant peu habitées ; l'urbanisation qui s'étend à l'ensemble du pays et qui se double de la transformation de bourgades rurales en communes de plein exercice ; la croissance du réseau routier jusque dans les parties du territoire auparavant isolées des centres urbains. Tandis que l'est du pays s'est longtemps considéré comme oublié et que la basse-Casamance demeure traversée de courants irrédentistes en partie dus à son éloignement du centre, le territoire national dans son ensemble semble rattrapé par des dynamiques spatiales qui ne concernaient que l'ouest du pays.

The study of life history traits and their covariations is critical to fully understand population demography and evolution. Among these traits, adult survival is central, as a component of fitness. Reproductive phenology is also a key element through its major consequences on fitness and through its sensitivity to environmental variations, particularly in the current context of climate change. The study of the relationship between these two traits is crucial in understanding the complex relationships between life history traits in a population. It is however surprisingly not often studied. This thesis aims to explore variations in survival in four populations of blue tit (Cyanistes caeruleus) in the Mediterranean region, and to examine the existence of links between survival and other demographic or environmental components of populations, including reproductive phenology. Using capture-mark-recapture models, we were able to estimate survival probabilities in the different populations. We showed that in one of these populations, the phenology of the population impacted adult survival at the population level (a decrease in the median laying date of the population causes a decrease in subsequent survival) as well as at the individual level (but in the opposite direction: the earliest individuals in the population are those who have the highest survival probabilities in the following year). These covariations are part of a complex relationship system that involves reproductive success (related to laying date), environment (which impacts laying date and reproductive success), and population density (which has negative effects on laying date, reproductive success and adult survival). In total, our work sheds new light on the processes related to adult survival and its spatial and temporal variations in the populations studied, as well as their links with environmental variations.; L’étude des traits d’histoires de vie des organismes et de leurs covariations est extrêmement informative sur la démographie des populations ainsi que sur leur évolution. Parmi ces traits, la survie adulte est centrale en tant que composante de la valeur sélective. La phénologie de la reproduction est également un élément clef par ses conséquences majeures sur la valeur sélective et sa sensibilité aux variations environnementales, notamment dans le contexte actuel de changement climatique. L’étude du lien entre ces deux traits est déterminante dans la compréhension des relations complexes entre traits d’histoires de vie dans une population, mais il reste cependant peu étudié. Cette thèse vise à explorer les variations de survie dans quatre populations de mésanges bleues (Cyanistes caeruleus) en région méditerranéenne, et à examiner l’existence de lien entre celle-ci et d’autres composantes démographiques ou environnementales des populations, notamment la phénologie de la reproduction. Grâce à des modèles de type capture-marquage-recapture, nous avons pu estimer les taux de survie dans les différentes populations. Nous avons montré que dans l’une de ces populations, la phénologie de la population impactait la survie adulte au niveau populationnel (une diminution de la date de ponte médiane de la population est liée à une diminution de la survie) ainsi qu’au niveau individuel en sens contraire (les individus les plus précoces au sein de la population sont ceux qui ont la survie la plus élevée dans l’année qui suit). Ces covariations s’inscrivent dans un système de relations complexe qui fait intervenir le succès reproducteur (lié à la date de ponte), l’environnement (effet sur la date de ponte et sur le succès reproducteur), et la densité de population (effets sur la date de ponte, le succès reproducteur et sur la survie adulte). Au total, nos travaux éclairent d’un jour nouveau les processus liés à la survie adulte et ses variations spatio-temporelles dans les populations étudiées, ainsi que leurs liens avec les variations environnementales.

The study of life history traits and their covariations is critical to fully understand population demography and evolution. Among these traits, adult survival is central, as a component of fitness. Reproductive phenology is also a key element through its major consequences on fitness and through its sensitivity to environmental variations, particularly in the current context of climate change. The study of the relationship between these two traits is crucial in understanding the complex relationships between life history traits in a population. It is however surprisingly not often studied. This thesis aims to explore variations in survival in four populations of blue tit (Cyanistes caeruleus) in the Mediterranean region, and to examine the existence of links between survival and other demographic or environmental components of populations, including reproductive phenology. Using capture-mark-recapture models, we were able to estimate survival probabilities in the different populations. We showed that in one of these populations, the phenology of the population impacted adult survival at the population level (a decrease in the median laying date of the population causes a decrease in subsequent survival) as well as at the individual level (but in the opposite direction: the earliest individuals in the population are those who have the highest survival probabilities in the following year). These covariations are part of a complex relationship system that involves reproductive success (related to laying date), environment (which impacts laying date and reproductive success), and population density (which has negative effects on laying date, reproductive success and adult survival). In total, our work sheds new light on the processes related to adult survival and its spatial and temporal variations in the populations studied, as well as their links with environmental variations.; L’étude des traits d’histoires de vie des organismes et de leurs covariations est extrêmement informative sur la démographie des populations ainsi que sur leur évolution. Parmi ces traits, la survie adulte est centrale en tant que composante de la valeur sélective. La phénologie de la reproduction est également un élément clef par ses conséquences majeures sur la valeur sélective et sa sensibilité aux variations environnementales, notamment dans le contexte actuel de changement climatique. L’étude du lien entre ces deux traits est déterminante dans la compréhension des relations complexes entre traits d’histoires de vie dans une population, mais il reste cependant peu étudié. Cette thèse vise à explorer les variations de survie dans quatre populations de mésanges bleues (Cyanistes caeruleus) en région méditerranéenne, et à examiner l’existence de lien entre celle-ci et d’autres composantes démographiques ou environnementales des populations, notamment la phénologie de la reproduction. Grâce à des modèles de type capture-marquage-recapture, nous avons pu estimer les taux de survie dans les différentes populations. Nous avons montré que dans l’une de ces populations, la phénologie de la population impactait la survie adulte au niveau populationnel (une diminution de la date de ponte médiane de la population est liée à une diminution de la survie) ainsi qu’au niveau individuel en sens contraire (les individus les plus précoces au sein de la population sont ceux qui ont la survie la plus élevée dans l’année qui suit). Ces covariations s’inscrivent dans un système de relations complexe qui fait intervenir le succès reproducteur (lié à la date de ponte), l’environnement (effet sur la date de ponte et sur le succès reproducteur), et la densité de population (effets sur la date de ponte, le succès reproducteur et sur la survie adulte). Au total, nos travaux éclairent d’un jour nouveau les processus liés à la survie adulte et ses variations spatio-temporelles dans les populations étudiées, ainsi que leurs liens avec les variations environnementales.

In Sub-Saharan Africa, population growth and climatic variability generate significant population movements in direction of protected areas. The installation on the periphery or inside the protected areas, exposes the human populations and the animals that they raise to the bite of insect-vectors able to transmitting pathogens (yellow fever, leishmaniasis, trypanosomosis etc.). This is the case of tsetse flies, vectors of Human African Trypanosomiasis (HAT or sleeping sickness) and African Animal Trypanosomosis (AAT). In Côte d’Ivoire, population increased from 2.6 million (8 people/km2) in 1950 to 23,1 million in 2015 (71,6 people/km2). The process of deforestation for agriculture development (coffee, cocoa, rubber tree and cashew plantations for example) have led to a land saturation, which are oriented agricultural populations towards protected areas. This increasing of anthropic impacts in and around protected areas exposes human and animal populations to tsetse fly bite and trypanosome risk. The objective of this study is to report the process of exploitation of territories situated in margins and inside two protected areas and to evaluate trypanosome risk. More precisely, the first step is to characterize settlement dynamics (creation, extension and multiplication of stands, increase in human population densities) and changes in the rural area (areas cultivated and types of crops) outskirts of the Taï National Park (forest) and the Comoé National Park (savannah). Activities carried out by the surrounding riparian populations and within these protected areas is also studied (gathering, hunting, fishing, grazing, gold panning, etc.). In the same time, in order to assess the risk, entomological surveys (species diversity, density and infection of tsetse flies), medical and veterinary surveys (seroprevalence, prevalence of HAT and AAT) were conducted. This "One Health" approach provides a better understanding of how populations exploit marginal and protected areas and measure trypanosome risk exposure. In view of the demographic projections and future land issues associated, this theme appears essential for the elimination of human and animal trypanosomiasis. This study helps to reach the goal of elimination of THA in Côte d'Ivoire by 2020., En Afrique subsaharienne, la croissance démographique et la variabilité climatique génèrent d’importants mouvements de population en direction des espaces protégés. L’installation en périphérie ou à l’intérieur de ces espaces, exposent les populations humaines et les animaux domestiques (qu’elles élèvent) à la piqûre d’insectes-vecteurs capables de transmettre des pathogènes (fièvre jaune, leishmanioses, trypanosomoses etc.). C’est le cas des glossines (ou mouches tsé-tsé), vecteurs de la Trypanosomiase Humaine Africaine (THA ou maladie du sommeil) et de la Trypanosomose Animale Africaine (TAA). En Côte d’Ivoire, la population est passée de 2,6 millions d’habitants (8 hab/km2) en 1950 à 23,1 millions d’habitants (71,6 hab/km2) en 2015. Le processus de déforestation en faveur de l’agriculture (plantations de café, de cacao, d’hévéas, d’anacardier etc.) a provoqué une saturation foncière qui a orienté les populations agricoles en direction des espaces protégés. Cette anthropisation croissante en marge et à l’intérieur des espaces protégés, exposent les populations humaines et animales domestiques à la piqûre des glossines et au risque trypanosomien. L’objectif de cette étude est de rendre compte des processus d’exploitation de territoires situés en marges et à l’intérieur de deux espaces protégés et d’évaluer le risque trypanosomien associé. Dans un premier temps, il s’agit de caractériser les dynamiques de peuplements (création, extension et multiplication des peuplements, augmentation des densités de populations humaines) et les évolutions de l’emprise rurale (superficies cultivées et types de cultures) en périphérie du Parc National de Taï (forêt) et du Parc National de la Comoé (savane). Les activités menées par les populations riveraines en périphérie et au sein de ces espaces protégés sont également étudiées (cueillette, chasse, pêche, pâturage, orpaillage, etc.). Parallèlement, afin d’évaluer le risque, des enquêtes entomologiques (diversité des espèces, densité et infection des glossines), médicales et vétérinaires (séroprévalence, prévalence de la THA et de la TAA) ont été menées. Cette approche « One Health », permet de mesurer l’exposition au risque trypanosomien, en tenant compte de la manière dont les populations humaines exploitent les territoires situés en marge et à l’intérieur d’espaces protégés. Au vu des projections démographiques et des questions foncières à venir qui leurs sont associées, cette thématique apparaît essentielle en vue de l’élimination des trypanosomoses humaines et animales.

International audience; Consiste en la correction d'une partie des analyses de comparaison de modèles statistiques.

Alors que le peuplement du territoire sénégalais se concentrait dans quelques parties du pays, plusieurs processus contemporains remettent en question la répartition spatiale de la population : la densification de zones auparavant peu habitées ; l'urbanisation qui s'étend à l'ensemble du pays et qui se double de la transformation de bourgades rurales en communes de plein exercice ; la croissance du réseau routier jusque dans les parties du territoire auparavant isolées des centres urbains. Tandis que l'est du pays s'est longtemps considéré comme oublié et que la Basse-Casamance demeure traversée de courants irrédentistes en partie dus à son éloignement du centre, le territoire national dans son ensemble semble rattrapé par des dynamiques spatiales qui ne concernaient que l'ouest du pays.

International audience; The aim of this study was to assess how soil organic C (SOC) stocks and earthworm communities were modified in agroforestry systems compared to treeless control plots and within the agroforestry plots (tree rows vs alleys). We used a network of 13 silvoarable agroforestry sites in France along a north/south gradient. Total earthworm abundance and biomass were significantly higher in the tree rows than those in the control plots, but were not modified in the alleys compared to those in the control plots. Earthworm species richness, Shannon index, and species evenness were significantly higher in the tree rows than those in the alleys. Total abundance of epigeic, epi-anecic, strict anecic, and endogeic was higher in the tree rows. Surprisingly, earthworm individual weight was significantly lower in the tree rows than that in the alleys and in the control plots. SOC stocks were significantly higher in the tree rows compared to that in the control plots across all sites. Despite higher SOC stocks in the tree rows, the amount of available C per earthworm individual was lower compared to those in the control. The absence of disturbance (no tillage, no fertilizers, no pesticides) in the tree rows rather than increased SOC stocks therefore seems to be the main factor explaining the increased total abundance, biomass, and diversity of earthworms. The observed differences in earthworm communities between tree rows and alleys may lead to modified and spatially structured SOC dynamics within agroforestry plots.

International audience

Understanding the mechanisms underlying the movements and spread of a species over time and space is a major concern of ecology. Here, we assessed the effects of an individual's sex and the density and sex ratio of conspecifics in the local and neighboring environment on the movement probability of the banana weevil, Cosmopolites sordidus. In a “two patches” experiment, we used radiofrequency identification tags to study the C. sordidus movement response to patch conditions. We showed that local and neighboring densities of conspecifics affect the movement rates of individuals but that the density‐dependent effect can be either positive or negative depending on the relative densities of conspecifics in local and neighboring patches. We demonstrated that sex ratio also influences the movement of C. sordidus, that is, the weevil exhibits nonfixed sex‐biased movement strategies. Sex‐biased movement may be the consequence of intrasexual competition for resources (i.e., oviposition sites) in females and for mates in males. We also detected a high individual variability in the propensity to move. Finally, we discuss the role of demographic stochasticity, sex‐biased movement, and individual heterogeneity in movement on the colonization process.

Recently, many countries have decided to reopen gradually and some of them have thought that social distancing has not had a significant effect. In our study, a new view of the importance of social distancing to prevent the spread of coronavirus has been presented in terms of the relationship between peak day and peak period and population density of nine countries. Data for nine different countries in different coronavirus situations have been analyzed. The analysis process was applied by using three programs, namely; WebPlotDigitizer, WSxM and Origin. The results provide evidence of the effectiveness of social distancing by calculation of the effect of population density on coronavirus infection. That was applied by two stages, the first one by determination of two different groups of countries depending on the rate and range of coronavirus spread. These two groups were countries with developed and developing COVID19 which lead to calculate the peak day and the period times of developed groups. Then, analysis of that data with population density was evaluated to indicate there are significant effects of population density on peak day and peak period times which explain the importance of social distancing between people to manage and control that. The results showed that there are increasing in peak day and peak period times with increasing the population density.Récemment, de nombreux pays ont décidé de rouvrir progressivement et certains d’entre eux ont estimé que la distanciation sociale n’avait pas eu d’effet significatif. Dans notre étude, une nouvelle vision de l’importance de la distanciation sociale pour prévenir la propagation du coronavirus a été présentée en termes de relation entre le jour et la période de pointe et la densité de population de neuf pays. Les données de neuf pays différents, dans des situations différentes en matière de coronavirus, ont été analysées. Le processus d’analyse a été appliqué en utilisant trois programmes, à savoir : WebPlotDigitizer, WSxM et Origin. Les résultats fournissent la preuve de l’efficacité de la distanciation sociale par le calcul de l’effet de la densité de population sur l’infection par le coronavirus. Cette méthode a été appliquée en deux étapes, la première consistant à déterminer deux groupes de pays différents en fonction du taux et de l’étendue de la propagation des coronavirus. Ces deux groupes étaient des pays avec des COVID19 développés et en développement, ce qui a permis de calculer le jour de pointe et les périodes des groupes développés. Ensuite, l’analyse de ces données avec la densité de population a été évaluée pour indiquer qu’il y a des effets significatifs de la densité de population sur les heures de pointe du jour et de la période de pointe qui expliquent l’importance de la distance sociale entre les personnes pour gérer et contrôler cela. Les résultats ont montré qu’il y a une augmentation de la densité de population dans les périodes de pointe et les jours de pointe.

Egg-size adjustment is one of the important plastic life-history traits for animals living in heterogeneous environments. The adaptive investment hypothesis predicts that mothers should increase progeny size according to certain cues predicting adverse future conditions of their offspring. However, reproductive resources are limited, and females have to simultaneously reduce egg number to allocate more resources to increase size. It remains unclear how single individuals alter egg size and number according to temporally heterogeneous environments. In the present study, we examined how desert locusts, Schistocerca gregaria, plastically alter egg size and number according to population density. We also investigated the trans-generational maternal effects on progeny characteristics as well as their own maternal physiological response (oviposition interval). Females kept in crowded conditions laid significantly larger and heavier eggs by reducing clutch size (number of eggs per egg pod) compared to isolated females, suggesting the existence of a reproductive trade-off between the two traits. The crowding-forced isolated females induced concerted changes not only in egg size but also in egg number tending towards those characteristics of gregarious control, implying that single individuals showed trade-off when egg size was increased. Double-blind testing confirmed the rapid crowding effects on egg size. Females also responded to crowding by extending the oviposition interval. As the oviposition interval extended, egg size increased, but clutch size decreased. Eggs from crowding-forced isolated females began to produce gregarious-phase type hatchlings (large and black) instead of solitarious-phase type ones (small and green). These results suggested that S. gregaria plastically manipulate egg size by regulating egg numbers and egg production rate, and indicated the presence of trans-generational maternal effects on progeny phase.

International audience; BackgroundIn a context of increasing resistance of both vectors toward main classes of insecticides used in public health and parasites toward anti-malarial drugs, development of new and complementary molecules or control approaches is fundamental to achieve the objective of controlling or even eliminating malaria. Concerning vector control, the sterile insect technique and other genetic control approaches are among promising complementary tools in an integrated management strategy for malaria control. These approaches rely not only on a good understanding of vector biology (especially during larval stages), but also on the availability of adequate supplies and protocols for efficient mosquito rearing. The aim of this study was to assess the factors impacting the life history of Anopheles coluzzii mosquitoes at the larval stage, in the context of genetic and sterile insect approaches to control malaria vectors.MethodsThe effect of different larval diets and larval rearing densities on the development of An. coluzzii were evaluated in the laboratory. Emergence rate (ER), pre-imaginal developmental time (DT) and adult wing length (WL) were measured under different food regimes. Four diets were tested among which three were provided by the Insect Pest Control Laboratory (IPCL) of the FAO/IAEA Joint division.ResultsData showed significant differences in the quality of the different diets and suggested a negative density dependence in all three life history parameters measured under tested rearing conditions. ER and WL increased with food availability, but decreased with increasing larval density. Conversely DT was shortened with increasing food availability but increased with larval density. These data demonstrates intraspecific larval competition modulated by food amount and space availability. Of the four diets tested, the one made of a mix of tuna meal, bovine liver powder, brewer's yeast, squid liver powder and vitamin mix (diet 2) yielded the best results as it produced a good balance between ER, DT and WL. Food availability for optimal development (highest survival at shortest time) was in the range of 180-400 mu g/larvae/day for the three diets provided by the IPCL.ConclusionThere is an interaction between diet type, diet concentration and larval density. Best results in terms of optimal larvae development parameters happen when moderately high values of those three variables are observed.

Des recherches pluridisciplinaires empiriques ont montré la complexité des liens entre dynamique démographique et production agricole. A travers deux exemples approfondis, nous illustrons dans cet article les transformations économiques et sociales qui permettent un maintien de la population en milieu rural dans un contexte de forte croissance démographique. A Kisii, au Kenya, comme dans le Vakinankaratra, à Madagascar, la diversification économique et des systèmes de mobilité temporaire ou de proximité sont de plus en plus courants. Les relations intergénérationnelles et de genre se transforment, comme les règles matrimoniales et celles qui dirigent la transmission des terres. En dehors de changements brutaux, politiques ou économiques, la population a une capacité à se transformer sans cesse, à innover, à faire évoluer ses normes sociales. Multidisciplinary field research programmes have shown the complexity of the interlinkages between population dynamics and agricultural production. Through two in-depth studies, we illustrate in this paper the social and economic changes that enable people to remain in rural areas undergoing high population growth. In Kisii, Kenya, and Vakinankaratra, Madagascar, economic diversification and spatial mobility systems involving temporary of short distance migration are of growing importance. Intergenerational and gender relationships are changing, as wan be seen in marriage and inheritance rules. Apart from cases of brutal economic or political change, societies have a capacity to transform, to innovate, to overstep its own norms.

International audience