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Mulot, Matthieu
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Mulot, Matthieu
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- PublicationAccès libreHigher spatial than seasonal beta diversity of soil protists along elevation gradients(2024)
; ; ; ; Biodiversity patterns along elevation gradients have long been studied for plants and animals, but only quite recently for soil microorganisms, especially protists (eukaryotes excluding plants, animals, and fungi). Microorganisms have shorter generation times than macroorganisms, and their abundance, diversity, and community structure are known to vary rapidly in response to abiotic and biotic factors. If microbial diversity varies more seasonally than spatially, a single sampling campaign along an elevation gradient, with contrasted phenologies, could introduce bias into biodiversity studies comparing multiple elevation gradients across different seasons, habitats, regions or latitudes. To address this question, we investigated the relative magnitude of spatial versus temporal diversity (alpha diversity) and community turnover (beta diversity) of soil protist communities along elevation gradients in two distant European mountain ranges. We collected soil samples in forests and grasslands below the treeline along five elevation gradients in two consecutive seasons (spring and summer) in the Spanish Sierra Nevada and the Swiss Alps, covering two distinct biogeographic regions. Using general eukaryotic primers and amplicon sequencing of soil environmental DNA, we decomposed total protist amplicon sequence variants diversity into local alpha- and beta diversity components and identified climatic and edaphic predictors of biodiversity patterns using redundancy analyses. Soil protist communities varied spatially within and among transects but temporal turnover was comparatively low. The best edaphic predictors of community variations were the same in spring and summer, but their explanatory power differed among seasons. The dominant spatial component of beta diversity suggests that patterns of soil protist communities along elevation gradients are more strongly driven by spatial heterogeneity than inter-seasonal turnover. Thus, in temperate climates, our results suggest that sampling only once between the end of spring and late summer across an elevation gradient does not introduce bias due to phenological differences when comparing beta diversity across multiple gradients. Spatio-temporal dynamics of soil protists communities were studied in forests and grasslands below the tree line along five elevation gradients in the Spanish Sierra Nevada and the Swiss Alps during two consecutive seasons (spring and summer). The total diversity of soil protist communities was predominantly shaped by beta-diversity components with spatial heterogeneity rather than temporal turnover as the main driver of soil protist community composition. Community dissimilarity of soil protists did not differ in response to temporal changes between habitats (i.e., forests versus grasslands) The significant edaphic predictors of protist community composition were highly similar in the Swiss Alps and identical in the Spanish Sierra Nevada between both seasons, but their explanatory power varied between spring and summer. Soil protist beta diversity patterns along different elevation gradients remained constant between seasons. This suggests that, in temperate climates, sampling at one time across an elevation gradient will not bias results stemming from phenological contrasts, allowing comparison of beta diversity patterns along such gradients between regions even if sampling is not simultaneous. - PublicationAccès libreAssessing the responses of Sphagnum micro-eukaryotes to climate changes using high throughput sequencing(2020-9-18)
; ; ; - PublicationAccès libreA worldwide survey of neonicotinoids in honey(2017-9-6)
; ; - PublicationAccès libreEffects of decomposing cadavers on soil nematode communities over a one-year period(2016-12-1)
; ; ; ; - PublicationAccès libreEffect of simulated climate change on the structure and functioning of Sphagnum peatlands-an experimental and modeling study(Neuchâtel : Université de Neuchâtel, Faculté des sciences, 2016)
; The main objective of this thesis was to investigate the response of Sphagnum dominated peatland to water table manipulations in an integrative approach. We conceived a mesocosms experiment that simulates artificial peatlands at different water regimes. We first show that our mesocosms behave according to the literature, with respiration and decomposition rates enhanced by the combined effects of water and temperature. We hypothesize that this C cycle dynamic is regulated by microbial activity. To address this question, we investigate the topological change of micro eukaryotic interaction network along the gradient and show that the structure of the network evolves along the gradient, showing a change point around -10 cm. Then we study the functional response of one functional group of micro eukaryotes, the testate amoebae. We show that environmental filtering constrained by manipulated water level promotes traits selection, and that this traits response can be used to mathematically model Hutchinson niche concept. Finally, we demonstrated the phenotypic plasticity on Hyalosphenia papilio, showing that traits selection acts both between species by community replacement, and within species by phenotypic plasticity. We propose a framework to model environmental filtering, integrating all components of this study. - PublicationAccès libreBio-inoculation of yerba mate seedlings (Ilex paraguariensis St. Hill.) with native plant growth-promoting rhizobacteria: a sustainable alternative to improve crop yield
; ; ; ; In this study, the role of native plant growth-promoting rhizobacteria (PGPR) as bio-inoculants was assessed as an alternative to ameliorate Ilex paraguariensis St. Hill. growth in nursery comparing poorer (soil) versus richer (compost) substrates. Twelve rhizospheric strains isolated from yerba mate plantations were evaluated in vitro for their potential as PGPRs. Three isolates, identified as Kosakonia radicincitans YD4, Rhizobium pusense YP3, and Pseudomonas putida YP2, were selected on the basis of their N2 fixation activity, IAA-like compound and siderophore production, and phosphate solubilization. A highly significant positive effect of bio-inoculation with the native isolates was observed in 5-month-old seedlings cultivated in soil. The highest increase was observed in seedlings inoculated with K. radicincitans YD4 with an increase of 183 % in the dry shoot weight and a 30 % increase in shoot N content. In contrast, in compost, no increment in the dry weight was observed; however, an increase in content in some macronutrients in shoots was observed. Remarkably, when plant biomass was compared between soil and compost, seedlings inoculated with K. radicincitans YD4 in soil produced the highest yields, even though higher yields could be expected in compost due to the richness of this substrate. In conclusion, bio-inoculation of yerba mate seedlings with native PGPR increases the yield of this crop in nursery and could represent a promising sustainable strategy to improve yerba mate growth in low-fertility soils. - PublicationAccès libreEukaryotic plankton diversity in the sunlit ocean
; ; - PublicationAccès libreResponse of Sphagnum Testate Amoebae to Drainage, Subsequent Re-wetting and Associated Changes in the Moss Carpet: Results from a Three Year Mesocosm Experiment
; ; Sphagnum peatlands represent a globally significant pool and sink of carbon but these functions are threatened by ongoing climate change. Testate amoebae are useful bioindicators of hydrological changes, but little experimental work has been done on the impact of water table changes on communities.
Using a mesocosm experimental setting that was previously used to assess the impact of drought disturbance on communities and ecosystem processes with three contrasted water table positions: wet (–4 cm), intermediate (–15 cm) and dry (–25 cm), we studied the capacity of testate amoeba communities to recover when the water table was kept at –10 cm for all plots. The overall experiment lasted three years. We assessed the taxonomic and functional trait responses of testate amoeba communities. The selected traits were hypothesised to be correlated to moisture content (response traits: shell size, aperture position) or trophic role (effect traits: mixotrophy, aperture size controlling prey range).
During the disturbance phase, the mixotrophic species Hyalosphenia papilio dominated the wet and intermediate plots, while the community shifted to a dominance of “dry indicators” (Corythion dubium, Nebela tincta, Cryptodifflugia oviformis) and corresponding traits (loss of mixotrophy, and dominance of smaller taxa with ventral or ventral-central aperture) in dry plots. During the recovery phase we observed two contrasted trends in the previously wet and intermediate plots: communities remained similar where the Sphagnum carpet remained intact but species and traits indicators of drier conditions increased in plots where it had degraded. In the former dry plots, indicators and traits of wet conditions increased by the end of the experiment.
This is one of the first experiment simulating a disturbance and subsequent recovery in ex-situ mesocosms of Sphagnum peatland focusing on the response of testate amoebae community structure as well as functional traits to water table manipulation. The results generally confirmed that testate amoebae respond within a few months to hydrological changes and thus represent useful bioindicators for assessing current and past hydrological changes in Sphagnum peatlands. - PublicationAccès libreCreation of a raised bog in the Botanical garden of Neuchâtel: a tool for research, collections and public information
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This object corresponds to the three missions of the garden : 1) to inform the public as well as students about these unusual, fragile and threatened ecosystems, 2) to present characteristic peatland plants from the Jura Mountains (Sphagnum, Drosera, Eriophorum, Betula nana, etc.), and 3) to conduct research projects.
During the winter 2014-15, the snow remained longer on the peatbog that on the adjacent path and meadow, thus providing evidence for a microclimatic effect of the bog. The excessively dry and hot summer 2015 allowed testing the resistance of the newly established bog vegetation. Most plants resisted well, including graminoids Eriophorum vaginatum, Trichophorum cespitosum or Carex sp., ericaceous (Vaccinium oxycoccos, myrtillus and vitis-idea) and mosses (especially Sphagnum). This living laboratory provides a unique opportunity to inform the public about the characteristics and functions of these ecosystems and the challenges of conserving and restoring them in a warmer world. - PublicationAccès libreA worldwide survey of neonicotinoids in honey
; ; ; Growing evidence for global pollinator decline is causing concern for biodiversity conservation and ecosystem services maintenance. Neonicotinoid pesticides have been identified or suspected as a key factor responsible for this decline. We assessed the global exposure of pollinators to neonicotinoids by analyzing 198 honey samples from across the world. We found at least one of five tested compounds (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam) in 75% of all samples, 45% of samples contained two or more of these compounds, and 10% contained four or five. Our results confirm the exposure of bees to neonicotinoids in their food throughout the world. The coexistence of neonicotinoids and other pesticides may increase harm to pollinators. However, the concentrations detected are below the maximum residue level authorized for human consumption (average ± standard error for positive samples: 1.8 ± 0.56 nanograms per gram).