Aebi, Alexandre

2022, Aebi, Alexandre, Hertz, Ellen

2019-11-1, Sutter, Louis, Aebi, Alexandre, Buchwalder, Gerald, Caballé, Pierre, Dietemann, Vincent, Girardin, Olivier, Hernandez, Julie, Jacopin-Bucher, Eloise, Mayor, Pascal, Ménétrier, Vanessa, Praz, Christophe, Varennes, Yann-David

2018-12-7, Sandau, Nadine, Naisbit, Russel E, Fabian, Yvonne, Bruggisser, Odile T, Kehrli, Patrick, Aebi, Alexandre, Rohr, Rudolf, Bersier, Louis-Felix

Studies on biodiversity–ecosystem functioning (BEF) in highly controlled experiments often yield results incompatible with observations from natural systems: experimental results often reveal positive relationships between diversity and productivity, while for natural systems, zero or even negative relationships have been reported. The discrepancy may arise due to a limited or closed local species pool in experiments, while natural systems in meta-community contexts experience dynamic processes, i.e., colonization and extinctions. In our study, we analysed plant community properties and above-ground biomass within a semi-natural (i.e., not weeded) experiment in an agricultural landscape. Eleven replicates with four different diversity levels were created from a species pool of 20 wildflower species. We found an overall significant negative relationship between total diversity and productivity. This relationship likely resulted from invasion resistance: in plots sown with low species numbers, we observed colonization by low-performing species; colonization increased species richness but did not contribute substantially to productivity. Interestingly, when analysing the biomass of the sown and the colonizer species separately, we observed in both cases positive BEF relationships, while this relationship was negative for the whole system. A structural equation modelling approach revealed that higher biomass of the sown species was linked to higher species richness, while the positive BEF relationship of the colonizers was indirect and constrained by the sown species biomass. Our results suggest that, in semi-natural conditions common in extensive agroecosystems, the negative BEF relationship results from the interplay between local dominant species and colonization from the regional species pool by subordinate species.

2018-6-27, Girod, Pierre, Borowiec, Nicolas, Buffington, Matthew, Chen, Guohua, Fang, Yuan, Kimura, Masahito T, Peris-Felipo, Francisco Javier, Ris, Nicolas, Wu, Hao, Xiao, Chun, Zhang, Jinping, Aebi, Alexandre, Haye, Tim, Kenis, Marc

Drosophila suzukii is an invasive fly of East Asian origin that has become a serious fruit pest worldwide. Classical biological control through the introduction of parasitoids from Asia could help reduce populations of D. suzukii in invaded regions. Little is known about the native parasitoids of the fly in Asia. Therefore, surveys for larval parasitoids of D. suzukii were carried out in China and Japan between 2015 and 2017. Parasitoids of D. suzukii and other fruit-inhabiting drosophilids (D. pulchrella and D. subpulchrella) that are probably attacked by the same parasitoid complex were found in four Chinese provinces and four Japanese prefectures. Larval parasitoids were obtained at most sites where D. suzukii was found, with parasitism varying from 0.0 to 75.6%. At least eight parasitoid species were reared. The most abundant and frequent parasitoids were the Figitidae Ganaspis cf. brasiliensis and Leptopilina japonica, but another Leptopilina species and at least five Braconidae species belonging to the genera Areotetes, Asobara and Tanycarpa were obtained in low numbers. Due to its likely restricted host range, the most promising parasitoid for biological control is Ganaspis cf. brasiliensis. However, its exact specificity and taxonomic status require future research.

2020-2-9, Aebi, Alexandre, Mitchell, Edward

Les études de l’impact des néonicotinoïdes sur les abeilles ont permis une prise de conscience sur la toxicité de ces molécules. Mais ces insectes ne sont pas les seuls à subir les conséquences de l’usage massif des pesticides en agriculture conventionnelle. En nous focalisant sur l’abeille, ne risque-t-on pas de négliger les effets sur les autres organismes vivants?

2019-2-5, Kammoun, Souad, Mulhauser, Blaise, Aebi, Alexandre, Mitchell, Edward, Glauser, Gaetan

Neonicotinoids and the closely related insecticide classes sulfoximines and butenolides have recently attracted growing concerns regarding their potential negative effects on non-target organisms, including pollinators such as bees. Indeed, it is becoming increasingly clear that these effects may occur at much lower levels than those considered to be safe for humans. To properly assess the ecological and environmental risks posed by neonicotinoids, appropriate sampling and analytical procedures are needed. Here, we used honey as reliable environmental sampler and developed an unprecedentedly sensitive method based on QuEChERS and UHPLC-MS/MS for the simultaneous determination of the nine neonicotinoids and related molecules currently present on the market (acetamiprid, clothianidin, dinotefuran, flupyradifurone, imidacloprid, nitenpyram, sulfoxaflor, thiacloprid and thiamethoxam). The method was validated and provided excellent levels of precision and accuracy over a wide concentration range of 3–4 orders of magnitude. Lowest limits of quantification (LLOQs) as low as 2–20 pg/g of honey depending on the analytes were reached. The method was then applied to the analysis of 36 honey samples from various regions of the World which had already been analysed for the five most common neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam) in a previous study. This allowed us to determine the long-term stability (i.e. up to 40 months) of these molecules in honey, both at room temperature and −20 °C. We found that the five pesticides were stable over a period of several years at −20 °C, but that acetamiprid and thiacloprid partially degraded at room temperature. Finally, we also measured the levels of dinotefuran, nitenpyram, sulfoxaflor and flupyradifurone and found that 28% of the samples were contaminated by at least one of these pesticides.

2018-11-25, Aebi, Alexandre, Mitchell, Edward

OPINION. Deux chercheurs de l’Université de Neuchâtel, Alexandre Aebi et Edward Mitchell, demandent à l’Office fédéral de l’agriculture de publier les informations détaillées sur l’usage des pesticides en Suisse, après une première communication insatisfaisante

2020-1-5, Hernandez, Julie, Maisonnasse, Albin, Cousin, Marianne, Beri, Constance, Le Quintrec, Corentin, Bouetard, Anthony, Castex, David, Decante, Damien, Servel, Elois, Buchwalder, Gerald, Brunet, Francois, Feschet-Destrella, Estelle, de Bellescize, Kiliana, Kairo, Guillaume, Frontero, Léa, Pédehontaa-Hiaa, Miren, Buisson, Robin, Pouderoux, Theo, Aebi, Alexandre, Kretzschmar, André

Methods for the evaluation and comparison of the structure of numerous honeybee colonies are needed for the development of applied and fundamental field research, as well as to evaluate how the structure and activity of honeybee colonies evolve over time. ColEval complements existing methods, as it uses an online reference image bank for (human) learning and training purposes. ColEval is based on the evaluation of the surface area percentage occupied by different components of a honeybee colony: adult worker bees, open and capped brood, honey, nectar, and pollen. This method is an essential tool for the description of the evolution in the size of honeybee colonies. The procedure makes allowances for tendencies between different observers and uses them to calculate accurate measurements of honeybee colony evaluation. ColEval thus allows for a posteriori comparison of under- or over-evaluation made by different observers working on the same project; it is thus possible to eliminate observer bias in the measurements and to conduct large surveys.

2019-1-21, Aebi, Alexandre

Des universitaires nous éclairent sur des sujets d’actualité, de société, ou de recherche. Aujourd’hui, Alexandre Aebi de l’Université de Neuchâtel évoque l’interdiction des pesticides dans le canton de Neuchâtel.

2018-11-1, Aebi, Alexandre, Moinet, Gabriel, Mitchell, Edward

Le déclin de la biodiversité et l’alté- ration des services écosystémiques mettent en péril la production à long terme de denrées alimentaires et de fourrage. Il est nécessaire de se tourner vers des systèmes de production agricole basés sur l’utili- sation de la diversité biologique et sur des écosystèmes en bon état de fonctionnement. L’agroécologie pro- pose de nouvelles solutions en la matière