L'impact des coupes forestières sur les communautés de Collemboles édaphiques de tourbière et de forêt à Bernadouze

National audienceLa tourbière de Bernadouze en Pyrénées ariégeoises est d'une richesse faunistique exceptionnelle. Elle est en particulier la zone humide la plus riche en collemboles connue à ce jour dans le monde. Sa microfaune terrestre, au sein de laquelle les collemboles jouent un rôle prépondérant, a été échantillonnée de façon approfondie depuis 2013. Une coupe forestière importante réalisée en 2016 par l'ONF sur les pentes boisées à proximité immédiate de la tourbière, s'est traduite par une ouverture importante du milieu, et un apport considérable de matériel ligneux au sol. Tirant parti de cette perturbation importante et de notre très bonne connaissance de la diversité faunistique de la forêt, nous avons lancé en 2018-2019 une campagne d'échantillonnage destinée à évaluer l'impact de cette coupe forestière sur la biodiversité des sols de forêt et de tourbière.La biodiversité de ces sols a été comparée avant et après la coupe forestière, apportant les premières données quantifiées sur la réponse d'un groupe édaphique majeur présent à la fois dans l'écosystème forestier directement perturbé et dans l'écosystème de tourbière adjacent non directement affecté.La diversité des communautés étudiées a, en forêt comme en tourbière, diminué très significativement suite à la coupe forestière de 2016: baisse modérée de la richesse spécifique globale (forêt et tourbière), mais baisse importante de la richesse moyenne par relevé (forêt et tourbière), baisse considérable des abondances, que ce soit globalement ou par relevé (forêt et tourbière), et changements importants dans la composition taxonomique des communautés (forêt). L'état actuel du sous-bois forestier et l'ouverture considérable du milieu, dont on connait l'importance pour les communautés édaphiques, suggèrent un impact direct de la coupe forestière sur la baisse de biodiversité des sols forestiers. On ne peut cependant exclure que les événements climatiques exceptionnels qui ont marqué la période d’échantillonnage, tout spécialement l'épisode caniculaire de 2019, aient pu aussi affecter fortement ces communautés, mais l'impact attendu eut là encore été moins marqué en tourbière qu'en forêt, en raison du rôle tampon des circulations hydriques. Suite à cette étude, un impact indirect de la coupe forestière sur la baisse de diversité en tourbière, à travers les flux hydriques forêt > tourbière apparaît comme une hypothèse de travail pertinente

Environmental variables and species traits as drivers of wild bee pollination in intensive agroecosystems—A metabarcoding approach

International audienceWild bees are known to be efficient pollinators of wild plants and cultivated crops and they are essential ecosystem service providers. However, wild bee populations have been suffering from significant declines in the last decades mainly due to the use of agrochemicals. Within this framework, we aimed to characterize wild bees' pollination spectrum (i.e., the community of pollinated flowering plants) in intensive agroecosystems, and describe the environmental variables and wild bee species traits influencing the pollination. To do this, we conducted metabarcoding analyses of pollen loads from wild bees collected in sunflower crops in the French region of Nouvelle-Aquitaine. Our study revealed that wild bees visited flowering plants corresponding to 231 different operational taxonomic units, classified into 38 families of which Asteraceae, Brassicaceae, and Apiaceae were the most visited and more than 90% of the visited taxa turned out to be wildflowers. We also analyzed the potential effect of environmental variables and wild bee species traits in governing their choice of pollinated plants. The community composition of pollinated plants varied depending on the flowering stages of the sunflower and the farming system. Our results also show that pollination niche breadth (alpha diversity) varied depending on the flowering stages of the sunflower but was not different between organic and conventional farming systems. Regarding wild bee species traits, the community composition of pollinated plants varied in relation to wild bees' body sizes and sociality levels. Our results are consistent with previous studies, suggesting that solitary bees are more specialist when it comes to flower selection than social bees, which are more generalist. The metabarcoding of pollen loads enabled us to draw a global picture of plant–wild bee interactions in an intensive agroecosystem. Our findings support the hypothesis that a higher diversity of weeds may increase wild bee diversity in intensive agroecosystem

Changes in Bacterial Community Structure Across the Different Life Stages of Black Soldier Fly (Hermetia illucens)

International audienceThe digestive capacity of organic compounds by the black soldier fly (BSF, Hermetia illucens, Diptera: Stratiomyidae, Linnaeus, 1758) is known to rely on complex larva-microbiota interactions. Although insect development is known to be a driver of changes of bacterial communities, the fluctuations along BSF life cycle in terms of composition and diversity of bacterial communities are still unknown. In this work, we used a metabarcoding approach to explore the differences in bacterial diversity along all four BSF developmental stages: eggs, larvae, pupae, and adult. We detected not only significant differences in bacterial community composition and species richness along the development of BSF, but also nine prevalent amplicon single variants (ASVs) forming the core microbiota. Out of the 2010 ASVs identified, 160 were significantly more abundant in one of the life stages. Moreover, using PICRUSt2, we inferred 27 potential metabolic pathways differentially used among the BSF life cycle. This distribution of metabolic pathways was congruent with the bacterial taxonomic distribution among life stages, demonstrating that the functional requirements of each phase of development are drivers of bacterial composition and diversity. This study provides a better understanding of the different metabolic processes occurring during BSF development and their links to changes in bacterial taxa. This information has important implications for improving bio-waste processing in such an economically important insect species

(Table 1) Characteristics of breeding male Adélie penguins (Pygoscelis adeliae) treated with varying degrees of corticosterone, Adélie land, Antarctica

Breeding individuals enter an emergency life-history stage when their body reserves reach a minimum threshold. Consequently, they redirect current activity toward survival, leading to egg abandonment in birds. Corticosterone (CORT) is known to promote this stage. How and to what extent CORT triggers egg abandonment when breeding is associated with prolonged fasting, however, requires further investigation. We manipulated free-living male Adelie penguins with CORT-pellets before their laying period. We then examined their behavioral response with respect to nest abandonment in parallel with their prolactin levels (regulating parental care), and the subsequent effects of treatment on breeding success in relieved birds. Exogenous CORT triggered nest abandonment in 60% of the treated penguins -14 days after treatment and induced a concomitant decline in prolactin levels. Interestingly, prolactin levels in treated penguins that did not abandon their nest were higher at the point of implantation and also after being relieved by females, when compared with abandoning penguins. Among successful birds, the treatment did not affect the number of chicks, nor the brood mass. Our results show the involvement of CORT in the decision-making process regarding egg abandonment in Adelie penguins when incubation is associated with a natural long fast. However, we suggest that CORT alone is not sufficient to trigger nest abandonment but that 1) prolactin levels need to reach a low threshold value, and 2) a rise in proteolysis (i.e. utilization of protein as main energy substrate) seems also to be required

Exogenous corticosterone and nest abandonment: A study in a long-lived bird, the Adélie penguin.

International audienceBreeding individuals enter an emergency life-history stage when their body reserves reach a minimum threshold. Consequently, they redirect current activity toward survival, leading to egg abandonment in birds. Corticosterone (CORT) is known to promote this stage. How and to what extent CORT triggers egg abandonment when breeding is associated with prolonged fasting, however, requires further investigation. We manipulated free-living male Adélie penguins with CORT-pellets before their laying period. We then examined their behavioral response with respect to nest abandonment in parallel with their prolactin levels (regulating parental care), and the subsequent effects of treatment on breeding success in relieved birds. Exogenous CORT triggered nest abandonment in 60% of the treated penguins ~14days after treatment and induced a concomitant decline in prolactin levels. Interestingly, prolactin levels in treated penguins that did not abandon their nest were higher at the point of implantation and also after being relieved by females, when compared with abandoning penguins. Among successful birds, the treatment did not affect the number of chicks, nor the brood mass. Our results show the involvement of CORT in the decision-making process regarding egg abandonment in Adélie penguins when incubation is associated with a natural long fast. However, we suggest that CORT alone is not sufficient to trigger nest abandonment but that 1) prolactin levels need to reach a low threshold value, and 2) a rise in proteolysis (i.e. utilization of protein as main energy substrate) seems also to be required

Exogenous corticosterone mimics a late fasting stage in captive Adelie penguins (Pygoscelis adeliae).

International audienceFasting is part of penguin's breeding constraints. During prolonged fasting three metabolic phases occur successively. Below a threshold in body reserves, birds enter phase III (PIII), which is characterized by hormonal and metabolic shifts. These changes are concomitant with egg abandonment in the wild and increased locomotor activity in captivity. Because CORT enhances foraging activity, we investigated the variations of endogenous CORT, and the effects of exogenous CORT on the behavioral, hormonal, and metabolic responses of failed breeder Adélie penguins. Untreated and treated captive male were regularly weighed and sampled for blood while fasting, and locomotor activity was recorded daily. Treated birds were implanted with various doses of CORT during phase II. Untreated penguins entering PIII had increased CORT (3.5-fold) and uric acid (4-fold; reflecting protein catabolism) levels, concomitantly with a rise in locomotor activity (2-fold), while prolactin (involved in parental care in birds) levels declined by 33 %. In CORT-treated birds, an inverted-U relationship was obtained between CORT levels and locomotor activity. The greatest increase in locomotor activity was observed in birds implanted with a high dose of CORT (C100), locomotor activity showing a 2.5-fold increase, four days after implantation to a level similar to that of birds in PIII. Moreover, uric acid levels increased 3-fold in C100-birds, while prolactin levels declined by 30 %. The experimentally-induced rise in CORT levels mimicked metabolic, hormonal, and behavioral changes characterizing late fasting, thus supporting a role for this hormone in the enhanced drive for refeeding occurring in long-term fasting birds

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

BackgroundWe previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15-20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in similar to 80% of cases.MethodsWe report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded.ResultsNo gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5-528.7, P=1.1x10(-4)) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR=3.70[95%CI 1.3-8.2], P=2.1x10(-4)). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR=19.65[95%CI 2.1-2635.4], P=3.4x10(-3)), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR=4.40[9%CI 2.3-8.4], P=7.7x10(-8)). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD]=43.3 [20.3] years) than the other patients (56.0 [17.3] years; P=1.68x10(-5)).ConclusionsRare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old