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29 juin 2018

High-throughput metabarcoding reveals the effect of physicochemical soil properties on soil and litter biodiversity and community turnover across Amazonia [PeerJ]

Subject areas : biodiversity, ecology, ecosystem science, microbiology, soil science

Knowledge on the globally outstanding Amazonian biodiversity and its environmental determinants stems almost exclusively from aboveground organisms, notably plants. In contrast, the environmental factors and habitat preferences that drive diversity patterns for micro-organisms in the ground remain elusive, despite the fact that micro-organisms constitute the overwhelming majority of life forms in any given location, in terms of both diversity and abundance. Here we address how the diversity and community turnover of operational taxonomic units (OTU) of micro-organisms in soil and litter respond to soil physicochemical properties ; whether OTU diversities and community composition in soil and litter are correlated with each other ; and whether they respond in a similar way to soil properties.(...)

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29 juin 2018

Assessing the impact of taxon resolution on network structure, with implication for comparative ecology [BioRxiv]

Constructing networks has become an indispensable approach in understanding how different taxa interact. However, methodologies vary widely among studies, potentially limiting our ability to meaningfully compare results. In particular, how network architecture is influenced by the extent to which nodes are resolved to either taxa or taxonomic units is poorly understood. To address this, here we collate nine datasets of ecological interactions, from both observations and DNA metabarcoding, and construct networks under a range of commonly-used node resolutions. We demonstrate that small changes in node resolution can cause wide variation in almost all key metric values, including robustness and nestedness.(...)

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29 juin 2018

Arbuscular mycorrhizal fungi : intraspecific diversity and pangenomes [New Phytologist]

Keywords : arbuscular mycorrhizal fungi (AMF), intraspecific diversity, pangenomes, Rhizophagus irregularis, transposable elements

Arbuscular mycorrhizal fungi (AMF) are ubiquitous plant symbionts with an intriguing population biology. Conspecific AMF strains can vary substantially at the genetic and phenotypic levels, leading to direct and quantifiable variation in plant growth. Recent studies have shown that high intraspecific diversity is very common in AMF, and not only found in model species. Studies have also revealed how the phenotype of conspecific isolates varies depending on the plant host, highlighting the functional relevance of intraspecific phenotypic plasticity for the AMF ecology and mycorrhizal symbiosis. Recent work has also demonstrated that conspecific isolates of the model AMF Rhizophagus irregularis harbor large and highly variable pangenomes, highlighting the potential role of intraspecific genome diversity for the ecological adaptation of these symbionts.

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28 juin 2018

Triggers of tree mortality under drought [Nature]

Severe droughts have caused widespread tree mortality across many forest biomes with profound effects on the function of ecosystems and carbon balance. Climate change is expected to intensify regional-scale droughts, focusing attention on the physiological basis of drought-induced tree mortality. Recent work has shown that catastrophic failure of the plant hydraulic system is a principal mechanism involved in extensive crown death and tree mortality during drought, but the multi-dimensional response of trees to desiccation is complex. Here we focus on the current understanding of tree hydraulic performance under drought, the identification of physiological thresholds that precipitate mortality and the mechanisms of recovery after drought. Building on this, we discuss the potential application of hydraulic thresholds to process-based models that predict mortality.

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28 juin 2018

Orangutans venture out of the rainforest and into the Anthropocene [Science Advances]

Conservation benefits from understanding how adaptability and threat interact to determine a taxon’s vulnerability. Recognizing how interactions with humans have shaped taxa such as the critically endangered orangutan (Pongo spp.) offers insights into this relationship. Orangutans are viewed as icons of wild nature, and most efforts to prevent their extinction have focused on protecting minimally disturbed habitat, with limited success. We synthesize fossil, archeological, genetic, and behavioral evidence to demonstrate that at least 70,000 years of human influence have shaped orangutan distribution, abundance, and ecology and will likely continue to do so in the future.(...)

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