SERG Final report: Ecosystemic impacts of forest tent caterpillar outbreaks

The forest tent caterpillar (Malacosoma disstria) is a significant defoliator of hardwoods throughout Canada. Historically, infestations usually collapsed after one or two years of defoliation, but longer and more severe outbreaks have been observed in recent years, leading to mortality of both sugar maple and trembling aspen, and making the forest tent caterpillar another pest whose impacts are increasing under a changing climate. This project examines how forest tent caterpillar outbreaks influence soil ecosystems, in both temperate deciduous and mixed boreal forests. We will assess inputs to soil ecosystems associated with forest tent caterpillar outbreaks and determine impacts on soil arthropod communities and tree regeneration. We also examine the different sources of mortality of the forest tent caterpillar colonies during and after the outbreak. It will thus provide empirical data to assess effects of forest tent caterpillar outbreaks on forest ecosystems and successional processes as well as population dynamics throughout the outbreaking cycle. Results suggest that defoliation favours the growth of non-host saplings. They also suggest that sources of mortality change during the different parts of the outbreak. Results will also contribute to the development of novel silvicultural approaches taking into account the effects of forest tent caterpillar outbreaks on forest regeneration and the need to keep process promoting regulation of forest tent caterpillar populations. La livrée des forêts (Malacosoma disstria) est un défoliateur important des forêts feuillues du Canada. Dans le passé, les épidémies s’effondraient généralement après une ou deux années de défoliation sans causer de dommages significatifs à la forêt, mais l’observation récente d’épidémies plus longues et plus sévères, suivies de mortalité des tiges de peuplier faux-tremble et d’érable à sucre, suggèrent que les impacts de la livrée des forêts, comme de plusieurs autres insectes ravageurs, augmentent en raison des changements climatiques. Ce projet examine les effets d’une épidémie de livrée des forêts sur l’écosystème du sol dans deux écosystèmes forestiers: la forêt feuillue et la forêt boréale mixte. Nous examinerons les apports en nutriments au sol associés aux épidémies de livrée et évaluerons les effets sur la communauté d’arthropodes du sol et sur la régénération des arbres. Nous avons aussi examiné les sources de mortalité des colonies de livrée des forêts durant et après l’épidémie. Les résultats fourniront des données empiriques pour évaluer les impacts des épidémies de livrée sur les écosystèmes forestiers et les processus de succession écologiques ainsi que les dynamiques de populations à travers les cycles épidémiques. Les résultats suggèrent que la défoliation peut bénéficier la croissance des jeunes arbres non-hôtes. Ils suggèrent aussi que les sources de mortalité diffèrent lors des différentes parties du cycles épidémiques. Les résultats contribueront aussi au développement d’approches sylvicoles qui prennent en considération le rôle de la livrée dans la régénération des forêts

IFN-Lambda (IFN-λ) Is Expressed in a Tissue-Dependent Fashion and Primarily Acts on Epithelial Cells In Vivo

Interferons (IFN) exert antiviral, immunomodulatory and cytostatic activities. IFN-α/β (type I IFN) and IFN-λ (type III IFN) bind distinct receptors, but regulate similar sets of genes and exhibit strikingly similar biological activities. We analyzed to what extent the IFN-α/β and IFN-λ systems overlap in vivo in terms of expression and response. We observed a certain degree of tissue specificity in the production of IFN-λ. In the brain, IFN-α/β was readily produced after infection with various RNA viruses, whereas expression of IFN-λ was low in this organ. In the liver, virus infection induced the expression of both IFN-α/β and IFN-λ genes. Plasmid electrotransfer-mediated in vivo expression of individual IFN genes allowed the tissue and cell specificities of the responses to systemic IFN-α/β and IFN-λ to be compared. The response to IFN-λ correlated with expression of the α subunit of the IFN-λ receptor (IL-28Rα). The IFN-λ response was prominent in the stomach, intestine and lungs, but very low in the central nervous system and spleen. At the cellular level, the response to IFN-λ in kidney and brain was restricted to epithelial cells. In contrast, the response to IFN-α/β was observed in various cell types in these organs, and was most prominent in endothelial cells. Thus, the IFN-λ system probably evolved to specifically protect epithelia. IFN-λ might contribute to the prevention of viral invasion through skin and mucosal surfaces

TRY plant trait database – enhanced coverage and open access

Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants - determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits - almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Delayed density dependence of various early-instar mortality sources during the crash of a forest tent caterpillar outbreak

Predation can be a major source of mortality in outbreaking pest insects and can help regulate the high densities of individuals at the peak of the outbreak. However, other mechanisms could be at play in the years of population crashing, contributing to the endemic levels of these populations. Forest tent caterpillars (Malacosoma disstria Hubner) are outbreaking pest species defoliating mixed wood boreal forests in eastern Canada, including Quebec. This species presents periodic population dynamics with peaks every 10 years and outbreaks lasting 1–3 years which can highly impact the health of its host tree. Different sources of mortality can play a role in the dynamics of these outbreaks such as extrinsic agents (natural enemies) and intrinsic ones (pathogens and maternal effect). Extrinsic mortality was considered in terms of natural enemies that can fly to reach the colony and those that have to walk to reach the prey. This study seeks to answer questions concerning the relative importance of these sources of mortality during and after the crash of an outbreak. We also investigated the difference between sites that had been defoliated during the last outbreak and those that were not to test for density dependence. For this experiment, we use a triad set-up of complete predator exclusion, partial exclusion and free colonies. We found that intrinsic mortality increases after the crash of the outbreak while only flighted mortality (related to parasitoids and other flying predators) did, and not walking mortality. There was no difference between the defoliated and control sites. These findings support our hypothesis that predation would increase after the outbreak and would lead to regulation of the population. However, we had underestimated the importance of intrinsic mortality for this regulation. This finding is important when thinking out potentially control agents to limit the spread of future outbreaks

Head injury profoundly affects gut microbiota homeostasis: Results of a pilot study

International audienceObjectives: Head injury (HI) induces a hypercatabolic state, dysimmunity, and septic complications that increase morbidity and mortality. Although compromised immune function is usually incriminated in infection occurrence, gut dysbiosis could also be involved in this phenomenon and, to our knowledge, has never been considered. To assess if HI could affect microbiota, we explored the impact of HI on intestinal microbiota in a rodent model of fluid percussion.Methods: Nineteen rats were randomly assigned to two groups: Healthy rats fed ad libitum (n ¼ 7) and HI rats (n ¼ 12), which received standard enteral nutrition for 4 d. Four days after HI, rats were euthanized and cecal contents were sampled. Cecal microbiota was assessed using real-timequantitative polymerase chain reaction.Results: HI significantly decreased the cecal content of strict anaerobic groups, Bacteroides/Prevotella group (HI 8.9 versus healthy controls 9.3 median log10 colony forming units [CFU]/g, P ¼ 0.007), Clostridium cluster XIVab (HI 7.9 versus healthy controls 8.9 median log10 CFU/g, P ¼ 0.002), Lactobacillus/Leuconostoc group (HI 8.5 versus healthy controls 9.4 median log10 CFU/g, P ¼ 0.044), and Bifidobacterium sp. (HI 3.0 versus healthy controls 8.2 median log10 CFU/g, P < 0.001). In contrast, colonization by Escherichia coli was dramatically increased (HI 10.5 versus healthy controls 7.0 median log10 CFU/g, P < 0.001).Conclusions: HI profoundly modified the gut microbiota homeostasis and thus could contribute to infection in head trauma patients. These preliminary results open a new field of research in the management of patients with HI