Impact des ressources florales et de nidification sur l'écologie de butinage et la structure des communautés des pollinisateurs à travers des paysages perturbés

Today, our societies are increasingly concerned about the alarming disappearance of insects. Yet they are essential to the proper functioning of our ecosystems, our food and our health. Pollinating insects such as bees, hoverflies and apoid wasps are also affected by this collapse. These insects generate significant ecosystem services for agriculture and the maintenance of natural areas through the pollination of flowering plants and the biological control of crops. A series of causes for these collapses have been widely documented in scientific literature, and it appears that it is mainly landscape degradation that is causing the greatest damage to biodiversity. Agricultural intensification and urbanization are converting complex natural areas into homogeneous, anthropogenic zones, thereby destroying floral and nesting resources, which are key components in the development and maintenance of pollinating insect communities. The homogenization of the landscape also alters the foraging behavior of our pollinating insects. It is in this context that this research thesis will focus, through 4 case studies, on the impact of landscape fragmentation on pollinator communities and foraging ecology in temperate zone of agricultural and urban landscapes. This thesis is structured around a general introduction (Chapter I), a general methodology (Chapter II) which introduces the technical tools shared between the different case studies, and four chapters constituting the core of this thesis (Chapter III-VI), the first two of which focus on agricultural landscapes, while the last two are more concerned with urban environments. The thesis concludes with a discussion, an outlook on future research and a general conclusion (Chapter VII). Chapter III looks at the influence of ecological diversification on the biodiversity of pollinators, particularly wild bees and hoverflies, on two farms in the early stages of ecological transition. This study has the merit of providing quality pollinator occurrence data based on standardized sampling techniques established over two years (2018-2019) and reports certain species that may be of conservation concern given their critical conservation status. In view of the specific diversity of wild bees present (101 species) and hoverflies (31 species), the ecological diversification of environments within the two sampled farms (e.g. wetlands, flower strips...) and agroecological practices may constitute new favorable environments for rare, oligolectic or endangered pollinator species. Building on the methodology and results of the previous chapter, in chapter IV we looked at the impact of a more specific floral resource supply practice: flower strips in intercropping systems with winter wheat. We found that a multifloral composition of flower strips attracted a greater diversity of hoverflies but not wild bees than monofloral oleaginous strips composed of Dimorphoteca pluvialis (Asteraceae) and Camelina sativa (Brassicacea). Finally, the ecological and economic benefits provided by these oleaginous flower strips are organized on three levels: (i) they provide alternative floral resources to pollinators; (ii) farmers are rewarded by the Agro-Environmental and Climate Measures (MAEC) of the European Union's Common Agricultural Policy; (iii) and farmers can generate additional income from the resale of harvested oleaginous seeds. In chapter V, we investigate urban landscapes. Pollen availability is a key factor influencing the population dynamics of pollinating insects in urban disturbed landscapes. In this study, we analyzed the foraged floral resources of honeybee colonies, Apis mellifera L., along an urban-rural gradient in a mega-city Tokyo (Japan). After a genomic analysis (i.e., metabarcoding) to identify the floral species foraged on the pollen samples, we showed that the landscape factor explains the differences in composition of the flowers visited and not their specific richness, whereas this richness is significantly dependent on the temporal factor. Honeybees forage more on woody species in spring, and more on herbaceous species in autumn. This study provides us with a better understanding of the urban needs of honeybees in a mega-city. Urban surfaces are commonly perceived as "ecologically impermeable" and can therefore represent a considerable obstacle to nesting opportunities for ground-nesting insects. In Chapter VI, we looked at the nesting alternative that pavements could offer for a range of ground-nesting Hymenoptera in the city of Brussels-Capital. Our study identified 22 species of wild bees and apoid wasps capable of nesting on Brussels sidewalks. These species mainly nested in old Brussels sidewalks made of sandstone pavers or concrete slabs with unbonded joints averaging one centimeter in width, and where the construction layers beneath the sidewalks were sandy in texture. At the end of this experiment, we were able to design technical recommendations and management practices to encourage these pollinating insects. The relevance of this research project and the general context are discussed at the end of this thesis in Chapter VII. Taken as a whole, these four studies underline the importance of food and nesting resources for insect pollinator communities and constitute milestones of knowledge providing further arguments in favor of the conservation and restoration of insect pollinators in disturbed environments We concluded this discussion with an open-minded outlook for the continuation scientific work in these topics of agricultural and urban ecology

Bandes fleuries, quels impacts sur les communautés d’auxiliaires de culture ?

Parmi les éléments semi-naturels dans les paysages agricoles, les bandes fleuries semées en inter-culture semblent être des refuges potentiels ainsi que des sources florales pour un bon nombre d’insectes, notamment les auxiliaires tels que les syrphes (Diptera : Syrphidae) ou encore les abeilles sauvages (Hymenoptera : Apoidea). Etant donné que ces insectes sont sensibles à une variété de traits floraux telles que la couleur ou encore la forme de la corolle, nous supposons qu’augmenter la diversité et la redondance de ces traits floraux (i.e. diversité fonctionnelle) favorisent et supportent une plus grande abondance et richesse spécifique d’auxiliaires de culture. Cet exposé aura pour but de vous montrer deux cas d’études de dispositifs de bandes enherbées et leur évaluation en Région Wallonne : (i) au niveau d’une ferme en transition agroécologique, la ferme d’Emeville (Havelange) et (ii) au niveau d’un champ expérimental à Golzinne (Gembloux). Les résultats seront montrés et discutés lors de la séance. Les méthodes utilisées ainsi que les résultats obtenus peuvent également constituer une base de développement concernant des nouveaux mélanges fleuris qui prodiguent deux services écosystémiques clés que sont la pollinisation et le contrôle biologique des cultures en milieu agricole

Inventaire de la faune apiforme (Hymenoptera, Apoidea) des quartiers Myosotis et Engeland à Uccle (Bruxelles, Belgique)

peer reviewedCe travail présente l’inventaire des abeilles sauvages (Hymenoptera Apoidea) observées dans l’ancien quartier Myosotis et le nouveau quartier Engeland de la commune d’Uccle à Bruxelles. Via une campagne d’échantillonnage dans les deux quartiers, 708 spécimens ont été capturés ou observés appartenant à 58 espèces différentes des 6 familles d’abeilles sauvages de Belgique. La faune apiforme capturée représente 14% de la faune belge et 28% de la faune bruxelloise. On y retrouve 10 espèces mono ou oligolectiques et 5 espèces font l’objet d’enjeux de conservation spécifiques selon la liste rouge des abeilles de Belgique. Quelques recommandations de gestion de conservation sont discutées dans ce travail en vue de favoriser au maximum la richesse de ces anthophiles pour la commune d’Uccle

Urban pavements as a novel habitat for wild bees and other ground-nesting insects

Municipal authorities around the world have come to recognize the importance of making conservation and restoration a priority. Multiple urban restoration programs now foster insects and other pollinators through planting and sowing flowering plants, many of them within residential areas. But residents are not only walking next to pollinators visiting flowering sidewalk grass verges, they are also walking on top of them, nesting in the cracks and interstices of urban pavements. Combining morphological and molecular monitoring schemes, we conducted a survey of urban pavements at twelve locations across Berlin and found that pavements can foster a surprising number and quantity of soil dwelling insects—in particular wild bees and wasps. Pavements located within 200 m to an insect-friendly flower garden were covered with significantly more nests of wild bees and solitary wasps, and showed higher species richness of these groups, while the degree of sealed surfaces in the surrounding had no effect per se. This underlines the positive impact that insect-friendly gardens can have for pollinators and other insects, even in highly sealed areas. Also, it shows the potential of cobbled pavements as valuable nesting sites in highly sealed urban areas. We provide a list of 55 species of ground-nesting Hymenoptera found in Berlin pavements, including 28 species of wild bees and 22 apoid wasps. In our study, the molecular approach only detected three Hymenoptera species and did not yield comparable results to classical monitoring. Nonetheless, using eDNA methods might be a promising tool for further studying soil nesting insects in the future, and to gain insights into the web of life in urban pavements

Investigating hoverfly responses to chemical cues and honeydew in agro-ecosystem

editorial reviewedPredatory insects play a pivotal role in regulating pest populations within agricultural crops. Among these, aphidophagous hoverflies are key insect vectors for controlling aphids in wheat crops. The initial attraction of hoverflies is facilitated by the honeydew secreted by aphid pests. Notably, certain bacteria present in aphid honeydew, such as Staphylococcus sciuri, generate chemically enticing compounds that effectively draw in aphidophagous hoverflies. Additionally, incorporating flower strips as intercrops enhances aphid regulation by attracting a greater number of natural enemies to control insect pests. To assess the predatory potential of aphidophagous insects, the oviposition behavior of the Episyrphus balteatus hoverfly was examined in a flight tunnel under various conditions. These conditions included fresh honeydew from Acyrthosiphon pisum and Aphis fabae, a filtered solution of S. sciuri bacteria, and a combination of chemical compounds—specifically, 3-methyl-2-butenal and 3-dimethyl-3,3 acrylic acid—released by S. sciuri. Field experiments involved applying this chemical compound mixture to experimental plots of camelina (Camelina sativa (L.)) and buckwheat (Fagopyrum esculentum Moench) sown in a wheat field at Gembloux (Wallonia, Belgium) to gauge the attraction of aphidophagous hoverflies. Results indicated no significant difference from negative controls, both in laboratory and field settings, with regard to the filtered bacterial solution and the specified chemical compounds. However, the oviposition behavior of E. balteatus hoverflies was observed to be stimulated by both types of honeydew tested. Consequently, exploring alternative methods for pest control through natural predators may diminish the reliance on widespread pesticide application in cultivated fields, potentially aiding in the conservation of biodiversity increasingly impacted by human activities.12. Responsible consumption and productio

They live under our streets: ant nests (Hymenoptera, Formicidae) in urban pavements

peer reviewedIn the context of global insect decline, the urbanisation process plays a key role. However, urban pavements, which are considered to be impervious to biodiversity, can harbour ground-nesting insects under certain conditions. Recent observations have revealed the presence of Formicidae nests under urban pavements. The aim of this work is to determine the species richness of Formicidae nesting under urban pavements in the Brussels-Capital Region (Belgium) and to characterise their nest environment and soil texture. Seven ant species were identified in 120 nesting sites: Lasius niger, Lasius brunneus, Lasius flavus, Lasius fuliginosus, Tetramorium caespitum, Tetramorium impurum and Myrmica rugulosa. Concrete slabs or natural stones with a sandy sub-layer are the main structures in which ants nest. In addition, nests were mainly found under modular pavements with degraded rigid joints. The results of this work highlight the capacity of urban structures to host part of ant biodiversity in cities

Evaluation de l'entomofaune associée au chou, Brassica oleracea L. var capitata dans l'Est de la RDCongo

peer reviewedCabbage is an important component of agriculture in the eastern Democratic Republic of Congo (DRC) for its various food uses. It is important to identify pests that affect its production, which is still insufficient to meet the increasing consumer needs. Furthermore, insect data for tropical agroecosystems, particularly those of DRC are limited, making insect diversity poorly understood. The objective of this study is to assess the diversity and abundance of entomofauna related to cabbage in five different cabbage growing sites: Minova, Sake, Kibumba, Rutshuru and Lac Vert. This was achieved by trapping insects with the sweep net and yellow pantraps during 2021 and 2022. A total of 1109 insects from 9 orders and 48 families were collected. The most abundant pest families were Ciccadellidae (8%), Coreidae (7%), Chysomelidae (5%) and Pentatomidae (4%). The main families of beneficial insects(natural enemies and pollinators) identified were Syrphidae (7%), Carabidae (4%), Coccinellidae (3%) and Apidae (3%). Insect communities found in different locations were similar and diversified. Considering functions played by these different functional groups as ecological indicators, it is important to preserve entomological biodiversity. This is achieved through the rational selection of pest management methods to optimize ecosystem services provided by beneficial insects.2. Zero hunger12. Responsible consumption and productio

Insect detection and counting from entomological collections using deep learning methods

editorial reviewedEntomological collections are invaluable repositories of biodiversity records, crucial for understanding the temporal and spatial distribution of insects, especially important given current concerns about the decline of insect populations. Despite ongoing digitization efforts in a lot of natural museums, a significant challenge remains in linking metadata to individual insect specimens stored in collection boxes. The automated detection of an insect specimen from a collection box can be a difficult task owing to the remarkable morphological diversity inherent to these organisms. The advent of convolutional neural networks (CNNs) have greatly propelled the field of computer vision, especially in object detection. In this research, deep learning approaches provide a simple basis for carrying out the task of insect detection and counting from high-resolution pictures of entomological collection. YOLOv8 and Faster R-CNN algorithms were selected to detect and count insect from Lepidoptera and Coleoptera orders by setting-up trained models over more than 80 insect families from Africa. Then, more than 7,900 pictures were confronted to pre-trained datasets in order to detect and isolate each insect specimen and, automatically count the insect number per boxes. A comparisons of both algorithms is discussed in term of precision and computing resources. Automated detection of insects in entomological collection pictures could be the first step for their taxonomical classification. In conclusion, the implementation of deep learning algorithms represents a significant step forward in the digitization and analysis of entomological collections, offering promising avenues for enhanced biodiversity research and conservation effort

Vécu des actions de prévention de la bilharziose urinaire à Kossou et Suibiakro

Résumé : La bilharziose urinaire est une maladie d'actualité en Côte d’Ivoire. Des études entomologiques ont montré que sa prévalence et son intensité sont maximales en milieu rural malgré les actions de prévention en vigueur. Cette étude socio-anthropologique vise à analyser le vécu des actions de prévention de la bilharziose urinaire à Kossou et Suibiakro, dans le district sanitaire de Yamoussoukro. De nature qualitative, elle a mobilisé diverses techniques de recherche à savoir : le focus-group, l’observation directe et l’entretien individuel. L’analyse des données a permis de comprendre que les attitudes des communautés face aux actions de prévention sont déterminées par leurs représentations de la bilharziose urinaire. En outre, elles sont le signe d’une résignation face à la précarité de l’environnement propice à cette maladie. A Suibiakro, la bilharziose urinaire n’est pas perçue comme une maladie mais plutôt un indicateur social de la puberté. En revanche, à Kossou, elle est perçue comme une maladie grave mais avec laquelle la communauté se dit être obligée de vivre en raison de la nature de leurs activités. Prônant la nécessité d’une lutte multidisciplinaire, cette étude postule l’importance de la socio-anthropologie de la santé dans la compréhension globale des MTN et dans l’identification de leviers pour une lutte intégrée et efficace. Mots-clés : Vécu, Actions, Prévention, Bilharziose urinaire, Côte d’Ivoir