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Rasmann, Sergio

Nom
Rasmann, Sergio
Affiliation principale
Site web
Fonction
Professeur Assistant
Email
sergio.rasmann@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/929

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  • Publication
    Accès libre
    Solar radiation explains litter degradation along alpine elevation gradients better than other climatic or edaphic parameters
    (2023-04-27)
    Semeraro, Sarah 
    ;
    Pascal Kipf
    ;
    Le Bayon, Renée-Claire 
    ;
    Rasmann, Sergio 
    Organic matter (OM) decomposition has been shown to vary across ecosystems, suggesting that variation in local ecological conditions influences this process. A better understanding of the ecological factors driving OM decomposition rates will allow to better predict the effect of ecosystem changes on the carbon cycle. While temperature and humidity have been put forward as the main drivers of OM decomposition, the concomitant role of other ecosystem properties, such as soil physicochemical properties, and local microbial communities, remains to be investigated within large-scale ecological gradients. To address this gap, we measured the decomposition of a standardized OM source – green tea and rooibos tea – across 24 sites spread within a full factorial design including elevation and exposition, and across two distinct bioclimatic regions in the Swiss Alps. By analyzing OM decomposition via 19 climatic, edaphic or soil microbial activity-related variables, which strongly varied across sites, we identified solar radiation as the primary source of variation of both green and rooibos teabags decomposition rate. This study thus highlights that while most variables, such as temperature or humidity, as well as soil microbial activity, do impact decomposition process, in combination with the measured pedo-climatic niche, solar radiation, very likely by means of indirect effects, best captures variation in OM degradation. For instance, high solar radiation might favor photodegradation, in turn speeding up the decomposition activity of the local microbial communities. Future work should thus disentangle the synergistic effects of the unique local microbial community and solar radiation on OM decomposition across different habitats.
  • Publication
    Accès libre
    Soil properties and plant species can predict population size and potential introduction sites of the endangered orchid Cypripedium calceolus
    (2023-2-16)
    Rusconi, Olivia 
    ;
    Steiner, Théo
    ;
    Le Bayon, Renée-Claire 
    ;
    Rasmann, Sergio 
    Background and Aims To counteract the ongoing worldwide biodiversity loss, conservation actions are required to re-establish populations of threatened species. Two key factors predominantly involved in finding the most suitable habitats for endangered plant species are the surrounding plant community composition and the physicochemical parameters of the soil rooting zone. However, such factors are likely to be context- and species-dependent, so it remains unclear to what extent they influence the performance of target species. Methods We studied large and small Swiss populations of the endangered orchid Cypripedium calceolus. We measured functional traits related to C. calceolus plant and population performance (clonal patch area, plant height, number, of leaf, stems, flowers and fruits), realized vegetation surveys, soil profile analyses, and tested for relationships between plant traits and the surrounding vegetation structure or soil physicochemical parameters. Results Large populations contained bigger patches with more stems and leaves, and produced more flower per individual than small populations. Neither vegetation alliances nor soil classes per se could predict C. calceolus functional traits and population size. However, functional traits explaining population performance and size were related to specific soil parameters (soil organic matter content, pH and phosphorus), in addition to a combination of presence-absence of plant indicator species, relating to ecotones between forests and clearings. Conclusion We show that even for species that can grow across a wide range of vegetation groups both indicator species and specific soil parameters can be used to assess the most favourable sites to implement (re)-introduction actions.
  • Publication
    Accès libre
    Effect of herbivore load on VOC-mediated plant communication in potato
    (2023)
    Carla Vázquez-González
    ;
    Violeta Quiroga
    ;
    Lucía Martín-Cacheda
    ;
    Rasmann, Sergio 
    ;
    Röder, Gregory 
    ;
    Luis Abdala-Roberts
    ;
    Xoaquín Moreira
    Herbivore-damaged plants emit volatile organic compounds (VOCs) that can alert neighbours and boost their resistance. While VOC-mediated plant communication has been shown to be herbivore-specific, we know little about its contingency on variation in herbivore load. To address this knowledge gap, we tested herbivore load effects on VOC-mediated communication between potato plants (Solanum tuberosum) using the generalist herbivore Spodoptera exigua. First, we tested whether herbivore load (three levels: undamaged control, low, and high load) affected total VOC emissions and composition. Second, we matched emitter and receiver plants and subjected emitters to the same herbivore load treatments. Finally, we performed a bioassay with S. exigua on receivers to test for induced resistance due to VOC-mediated communication. We found that herbivory significantly increased total VOC emissions relative to control plants, and that such increase was greater under high herbivore load. In contrast, we found no detectable effect of herbivory, regardless of the load, on VOC composition. The communication experiment showed that VOCs released by herbivore-induced emitters boosted resistance in receivers (i.e., lower leaf damage than receivers exposed to VOCs released by control emitters), but the magnitude of such effect was similar for both levels of emitter herbivore load. These findings suggest that changes in VOCs due to variation in herbivore load do not modify the outcomes of plant communication.
  • Publication
    Accès libre
    Detecting preservation and reintroduction sitesfor endangered plant species using a two-step modelingand field approach
    (2022-8-10)
    Rusconi, Olivia 
    ;
    Broennimann, Olivier
    ;
    Storrer, Yannick
    ;
    Le Bayon, Renée-Claire 
    ;
    Guisan, Antoine
    ;
    Rasmann, Sergio 
    To withstand the surge of species loss worldwide, (re)introduction of endan-gered plant species has become an increasingly common technique in conser-vation biology. Successful (re)introduction plans, however, require identifyingsites that provide the optimal ecological conditions for the target species tothrive. In this study, we propose a two-step approach to identify appropriate(re)introduction sites. The first step involves modeling the niche and distribu-tion of the species with bioclimatic and topographical predictors, both at conti-nental and at national scales. The second step consists of refining thesebioclimatic predictions by analyzing stationary ecological parameters, such assoil conditions, and relating them to population-level fitness values. We dem-onstrate this methodology using Swiss populations of the lady's slipper orchid(Cypripedium calceolusL., Orchidaceae), for which conservation plans haveexisted for years but have generally been unfruitful. Our workflow identifiedsites for future (re)introductions based on the species requirements for mid-to-sunny light conditions and specific soil physico-chemical properties, such asbasic to neutral pH and low soil organic matter content. Our findings showthat by combining wide-scale bioclimatic modeling with fine scale field mea-surements it is possible to carefully identify the ecological requirements of atarget species for successful (re)introductions.
  • Publication
    Accès libre
    Transcriptomic analysis of deceptively pollinated Arum maculatum (Araceae) reveals association between terpene synthase expression in floral trap chamber and species-specific pollinator attraction
    (2022-7-21)
    Szenteczki, Mark 
    ;
    Godschalx, Adrienne 
    ;
    Gauthier, Jérémy
    ;
    Gibernau, Marc
    ;
    Rasmann, Sergio 
    ;
    Alvarez, Nadir
    Deceptive pollination often involves volatile organic compound emissions that mislead insects into performing nonrewarding pollination. Among deceptively pollinated plants, Arum maculatum is particularly well-known for its potent dung-like volatile organic compound emissions and specialized floral chamber, which traps pollinators—mainly Psychoda phalaenoides and Psychoda grisescens—overnight. However, little is known about the genes underlying the production of many Arum maculatum volatile organic compounds, and their influence on variation in pollinator attraction rates. Therefore, we performed de novo transcriptome sequencing of Arum maculatum appendix and male floret tissue collected during anthesis and postanthesis, from 10 natural populations across Europe. These RNA-seq data were paired with gas chromatography–mass spectrometry analyses of floral scent composition and pollinator data collected from the same inflorescences. Differential expression analyses revealed candidate transcripts in appendix tissue linked to malodourous volatile organic compounds including indole, p-cresol, and 2-heptanone. In addition, we found that terpene synthase expression in male floret tissue during anthesis significantly covaried with sex- and species-specific attraction of Psychoda phalaenoides and Psychoda grisescens. Taken together, our results provide the first insights into molecular mechanisms underlying pollinator attraction patterns in Arum maculatum and highlight floral chamber sesquiterpene (e.g. bicyclogermacrene) synthases as interesting candidate genes for further study.
  • Publication
    Accès libre
    Arbuscular mycorrhizal fungi prevent the negative effect of drought and modulate the growth-defence trade-off in tomato plants
    (2022-6-6)
    Orine, Dimitri 
    ;
    Defossez, Emmanuel 
    ;
    Vergara, Fredd
    ;
    Uthe, Henriette
    ;
    van Dam, Nicole M.
    ;
    Rasmann, Sergio 
    Introduction A wide range of arbuscular mycorrhizal fungi (AMF) can be applied to agricultural soils as biofertilizers for increasing crop growth and yield. Current research also shows that AMF can stimulate plant defences against a range of herbivores and pathogens. However, to date, the efficient use of AMF in agriculture is largely impaired by our inability to predict the performance of different AMF-plant complexes in variable environments. For instance, AMFs by increasing plant foraging capacity might alleviate allocation constraints in relation to growth versus defences. However, whether this effect occurs might depend on the in situ conditions. The main goal of this study was to investigate the context-dependency of the ability of AMF to modulate plant growth and resistance against herbivores under variable soil water availability. Materials and Methods To address our goal, we performed a greenhouse experiment for measuring the effect of different AMF inocula (Funneliformis mosseae, Rhizophagus irregularis, or both) on tomato plants (Solanum lycopersicum) growth and defences against an insect herbivore under two conditions: a normal watering regime or drought conditions. We measured the functional, physiological and chemical traits of the plants. Results We found that AMF presence generally decreased plant growth, but increased chemical defences and resistance against generalist caterpillars. Such growth-defence trade-off was nonetheless dependent on the identity of the mycorrhizal inoculum and on soil water content. Under drought, inoculated tomato plants lowered their investment to defence and noninoculated plants lowered their growth. Conclusion This study highlights the influence of abiotic factors and fungal identity on plant–AMF–herbivore interactions. In a broader sense, our results point to the necessity of finding AMF species that have reduced context-dependency to climatic factors, for more widespread use in organic agriculture.
  • Publication
    Accès libre
    Relative contribution of high and low elevation soil microbes and nematodes to ecosystem functioning
    (2022-1-7)
    Semeraro, Sarah 
    ;
    Kergunteuil, Alan 
    ;
    Sánchez-Moreno, Sara
    ;
    Puissant, Jérémy
    ;
    Goodall, Tim
    ;
    Griffiths, Robert
    ;
    Rasmann, Sergio 
    Ecosystem productivity is largely dependent on soil nutrient cycling which, in turn, is driven by decomposition rates governed by locally adapted below-ground microbial and soil communities. How climate change will impact soil biota and the associated ecosystem functioning, however, remains largely an open question. To address this gap, we first characterized differences in soil microbial and nematode communities as well as functional characteristics from soils collected from the foothills or in sub-alpine elevations of the Alps. We next performed a full-factorial reciprocal transplant common garden experiment at two elevations, and asked whether elevation-related functional and taxonomic differences are maintained or can be altered depending on the local climatic conditions. For this, we separately transplanted soil microbial and nematode communities from low and high elevation in their home or opposite elevation in pots added with a common plant community. We found evidence for taxonomic and functional differentiation of the microbial and nematode communities when collected at high or low elevation. Specifically, we observed a decrease in microbial diversity and activity at high elevation, and additionally, through nematodes' functional characterization, we found increased fungal-dominated energy channels at high elevation. Moreover, according to the reciprocal transplant experiment, while we found little effect of soil biodiversity change based on elevation of origin on plant growth and plant community composition, soils inoculated with microbes originating from low elevation respired more than those originating from high elevation, particularly when at low elevation. This observation correlates well with the observed faster carbon degradation rates by the low elevation microbial communities. Climate change can reshuffle soil communities depending on organism-specific variation in range expansion, ultimately affecting soil fertility and carbon-cycle dynamics.
  • Publication
    Accès libre
    Downregulation of the photosynthetic machinery and carbon storage signaling pathways mediate La2O3 nanoparticle toxicity on radish taproot formation
    (2021-6-5)
    Xiao, Zhenggao
    ;
    Yue, Le
    ;
    Wang, Chuanxi
    ;
    Chen, Feiran
    ;
    Ding, Ying
    ;
    Liu, Yinglin
    ;
    Cao, Xuesong
    ;
    Chen, Zhe
    ;
    Rasmann, Sergio 
    ;
    Wang, Zhenyu
  • Publication
    Accès libre
    Spatial and temporal heterogeneity in pollinator communities maintains within-species floral odour variation
    (2021-5-25)
    Szenteczki, Mark 
    ;
    Godschalx, Adrienne 
    ;
    Galmán, Andrea
    ;
    Espíndola, Anahí
    ;
    Gibernau, Marc
    ;
    Alvarez, Nadir
    ;
    Rasmann, Sergio 
    Flowering plants emit complex bouquets of volatile organic compounds (VOCs) to mediate interactions with their pollinators. These bouquets are undoubtedly influenced by pollinator-mediated selection, particularly in deceptively-pollinated species that rely on chemical mimicry. However, many uncertainties remain regarding how spatially and temporally heterogeneous pollinators affect the diversity and distribution of floral odour variation. Here, we characterized and compared the floral odours of ten populations of deceptively-pollinated Arum maculatum (Araceae), and inter-annual and decadal variation in pollinator attraction within these populations. Additionally, we transplanted individuals from all sampled populations to two common garden sites dominated by different pollinator species (Psychoda phalaenoides or Psycha grisescens), and compared pollinator attraction rates to investigate whether populations maintained odour blends adapted to a specific pollinator. We identified high within- and among-population variation in a common blend of VOCs found across the range of A. maculatum. We also observed shifts in pollinator community composition within several populations over 1–2 years, as well as over the past decade. Common garden experiments further revealed that transplanted inflorescences generally attracted the dominant local pollinator species in both transplant sites. However, one population (Forêt du Gâvre, France) appears to exclusively attract P. grisescens, even when transplanted to a P. phalaenoides-dominated site. Together, our results suggest that maintaining diverse floral odour bouquets within populations may be advantageous when pollinator communities vary over short timescales. We propose that temporally-replicated ecological data are one potential key to understanding variation in complex traits such as floral odour, and in some cases may reveal resiliency to shifting pollinator communities.
  • Publication
    Accès libre
    Spatial and evolutionary predictability of phytochemical diversity
    (2021-1-19)
    Defossez, Emmanuel
    ;
    Pitteloud, Camille
    ;
    Descombes, Patrice
    ;
    Glauser, Gaétan
    ;
    Allard, Pierre-Marie
    ;
    Walker, Tom W. N.
    ;
    Fernandez-Conradi, Pilar
    ;
    Wolfender, Jean-Luc
    ;
    Pellissier, Loïc
    ;
    Rasmann, Sergio