Résumé
Understanding the relationship between morphology and movement in biomechanical systems, particularly those composed of multiple complex elements, presents challenges due to the nonlinear nature of the interaction between components. This study focuses on the mandibular closing mechanisms in ants, specifically comparing muscle-driven actuation (MDA) and latch-mediated spring actuation (LaMSA) in the genus Strumigenys. Analyzing 3D structural data from diverse Strumigenys species, we employ mathematical models for both LaMSA and MDA systems. Our findings reveal distinct patterns of mechanical sensitivity between the two models, with sensitivity varying across kinematic output metrics. We explore the performance transition between MDA and LaMSA systems by incorporating biological data and correlations between morphological parameters into the models. In these models tuned specifically to Strumigenys, we find the LaMSA mechanism outperforms MDA at small relative mandible mass. Notably, the location and abruptness of the performance transition differs among various kinematic performance metrics. Overall, this work contributes a novel approach to understanding form-function relationships in complex biomechanical systems. By using morphological data to calibrate a general biomechanical model for a particular group, it strikes a balance between simplicity and specificity and allows for conclusions that are uniquely tuned to the morphological characteristics of the group.Competing Interest StatementThe authors have declared no competing interest.
Auteurs, date et publication :
Auteurs Philip S L Anderson , Justin F Jorge , Stephanie B Crofts , Jackson T Castro , Rosalie L Didcock , Andrés Cook , Fredrick J Larabee , Mark Ilton
Publication : bioRxiv
Date : 2024
Pages : 2024.02.15.580213
Catégorie(s)
#CNRS #FORET NouraguesRésumé
In the context of current climate change, municipalities tend to plant more trees in order to benefit from services they provide in urban areas, such as reducing heat islands. However, in cities, trees are subject to severe abiotic constraints, the main ones being soil contamination and the lack of water due to soil compaction and droughts. This can negatively impact the ecological services provided by trees. Our study aims to help managers in monitoring the phytosanitary status of trees in order to be able to react promptly. In a controlled condition experiment, different plant compounds were analyzed (proline, malondialdehyde-MDA, photosynthetic pigments) in the leaves of young linden trees conventionally grown for planting by the City of Paris, France. They were grown on a trace element (TE) contamination soil gradient, and under different water regimes (well-hydrated/no water stress (Ct), dehydration (Dh), rehydration (Rh)) to see if tested compounds could be early stress markers in trees. Chlorophylls (Chl) could be considered as water and TE-mediated stress markers. Indeed Chl a and b concentrations significantly decreased with dehydration (e.g. respectively -34 % and -24 %) and increasing lead concentration in leaves (respectively, correlation coefficients were -1.08; -0.64 (p < 0.001)). On the contrary, Chl concentrations increased with increasing copper concentration in optimal physiological ranges (correlation coefficients for Chla and Chb were respectively 1.3 and 1.08 (p < 0.05)). Proline and malondialdehyde seemed to be good complementary markers of water stress in the Tilia genus. Indeed, proline concentration increased during the dehydration period (early water stress marker) (mean concentration for Ct, Dh and Rh trees were respectively 3.6, 29.6 and 51.3 mu mol.g(-1) DW), while MDA increased during the rehydration process (marker for stress accumulation over time) (mean concentration for Ct, Dh, and Rh were respectively 461.8, 313.9 and 493.5 nmol.g(-1) DW). In order to reinforce the diagnoses of urban tree managers, these stress indicators should be tested in situ.
Auteurs, date et publication :
Auteurs Iry Andrianjara , Cecile Cabassa , Jean-Christophe Lata , Amandine Hansart , Xavier Raynaud , Mathilde Renard , Francois Nold , Patricia Genet , Severine Planchais
Publication : ECOLOGICAL INDICATORS
Date : 2024
Volume : 158
Catégorie(s)
#ANR-Citation #CEREEP #CNRS #ENSRésumé
In some angiosperm species, especially in the Malvaceae family, postural control and directional growth of the stem are enabled by the mechanical interaction between the growing cambium and the secondary phloem. A key feature of this motor mechanism is the ability to redirect the tangential stress induced in secondary phloem into a longitudinal stress enabling the control of stem orientation. Here we studied how the microstructure of the secondary phloem is optimized for this function. We measured the longitudinal-tangential Poisson’s ratio and the longitudinal modulus of elasticity of secondary phloem in 22 tree species including Malvaceae and other families. We modeled the microstructure of Malvaceae secondary phloem using finite elements. The Poisson’s ratio of secondary phloem from Malvaceae trees was found one to two orders of magnitude higher than for other species, reaching the highest values ever reported for a natural material. Mechanical modeling confirmed these results and showed that parameters of the microstructure of secondary phloem are set at value optimizing this Poisson’s ratio. This highlights that the specific microstructure of Malvaceae secondary phloem is designed to maximize the conversion of cambial growth pressure into a longitudinal mechanical stress enabling the directional growth.
Auteurs, date et publication :
Auteurs Tancrède Alméras , Stéphane Corn , Anne Baranger , Arnaud Regazzi , Jonathan Barés , Romain Lehnebach , Bruno Clair
Publication : Trees
Date : 2025
Volume : 38
Issue : 6
Pages : 1379-1390
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Tropical rainforests are among the most emblematic ecosystems in terms of biodiversity. However, our understanding of the structure of tropical biodiversity is still incomplete, particularly for certain groups of soil organisms such as earthworms, whose importance for ecosystem functioning is widely recognised. This study aims at determining the relative contribution of alpha and beta components to earthworm regional diversity at a hierarchy of nested spatial scales in natural ecosystems of French Guiana. For this, we performed a hierarchical diversity partitioning of a large dataset on earthworm communities, in which DNA barcode-based operational taxonomic units (OTUs) were used as species surrogates. Observed regional diversity comprised 256 OTUs. We found that alpha diversity was lower than predicted by chance, regardless of the scale considered. Community-scale alpha diversity was on average 7 OTUs. Beta diversity among remote landscapes was higher than expected by chance, explaining as much as 87% of regional diversity. This points to regional mechanisms as the main driver of species diversity distribution in this group of organisms with low dispersal capacity. At more local scales, multiplicative beta diversity was higher than expected by chance between habitats, while it was lower than expected by chance between communities in the same habitat. This highlights the local effect of environmental filters on the species composition of communities. The calculation of a Chao 2 index predicts that as much as 1,700 species could be present in French Guiana, which represents a spectacular increase compared with available checklists, and calls into question the commonly accepted estimates of global number of earthworm species.Competing Interest StatementThe authors have declared no competing interest.
Auteurs, date et publication :
Auteurs Arnaud Goulpeau , Mickaël Hedde , Pierre Ganault , Emmanuel Lapied , Marie-Eugénie Maggia , Eric Marcon , Thibaud Decaëns
Publication : bioRxiv
Date : 2024
Pages : 2024.09.13.612984
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Parent-offspring interactions constitute the first contact of many newborns with their environment, priming community assembly of microbes through priority effects. Early exposure to microbes can have lasting influences on the assembly and functionality of the host’s microbiota, leaving a life-long imprint on host health and disease. Studies of the role played by parental care in microbial acquisition have primarily focused on humans and hosts with agricultural relevance. Anuran vertebrates offer the opportunity to examine microbial community composition across life stages as a function of parental investment. In this study, we investigate vertical transmission of microbiota during parental care in a poison frog (Family Dendrobatidae), where fathers transport their offspring piggyback-style from terrestrial clutches to aquatic nurseries. We found that substantial bacterial colonization of the embryo begins after hatching from the vitelline envelope, emphasizing its potential role as microbial barrier during early development. Using a laboratory cross-foster experiment, we demonstrated that poison frogs performing tadpole transport serve as a source of skin microbes for tadpoles on their back. To study how transport impacts the microbial skin communities of tadpoles in an ecologically relevant setting, we sampled frogs and tadpoles of sympatric species that do or do not exhibit tadpole transport in their natural habitat. We found more diverse microbial communities associated with tadpoles of transporting species compared to a non-transporting frog. However, we detected no difference in the degree of similarity between adult and tadpole skin microbiotas, based on whether the frog species exhibits transporting behavior or not. Using a field experiment, we confirmed that tadpole transport can result in the persistent colonization of tadpoles by isolated microbial taxa associated with the caregiver’s skin, albeit often at low prevalence. This is the first study to describe vertical transmission of skin microbes in anuran amphibians, showing that offspring transport may serve as a mechanism for transmission of parental skin microbes. Overall, these findings provide a foundation for further research on how vertical transmission in this order impacts host-associated microbiota and physiology.Competing Interest StatementThe authors have declared no competing interest.
Auteurs, date et publication :
Auteurs Marie-Therese Fischer , Katherine S. Xue , Elizabeth K. Costello , Mai Dvorak , Gaëlle Raboisson , Anna Robaczewska , Stephanie N. Caty , David A. Relman , Lauren A. O’Connell
Publication : bioRxiv
Date : 2024
Pages : 2024.09.11.612488
Catégorie(s)
#CNRS #FORET NouraguesRésumé
One foundational assumption of trait-based ecology is that traits can predict species demography. However, the links between traits and demographic rates are, in general, not as strong as expected. These weak associations may be due to the use of traits that are distantly related to performance, and/or the lack of consideration of size-related variations in both traits and demographic rates. Here, we examined how wood traits were related to demographic rates in 19 tree species from a lowland forest in eastern Amazonia. We measured 11 wood traits (i.e. structural, anatomical and chemical traits) in sapling, juvenile and adult wood; and related them to growth and mortality rates (MR) at different ontogenetic stages. The links between wood traits and demographic rates changed during tree development. At the sapling stage, relative growth rates (RGR) were negatively related to wood specific gravity (WSG) and total parenchyma fractions, while MR decreased with radial parenchyma fractions, but increased with vessel lumen area (VA). Juvenile RGR were unrelated to wood traits, whereas juvenile MR were negatively related to WSG and axial parenchyma fractions. At the adult stage, RGR scaled with VA and wood potassium concentrations. Adult MR were not predicted by any trait. Overall, the strength of the trait-demography associations decreased at later ontogenetic stages. Our results indicate that the associations between traits and demographic rates can change as trees age. Also, wood chemical or anatomical traits may be better predictors of growth and MR than WSG. Our findings are important to expand our knowledge on tree life-history variations and community dynamics in tropical forests, by broadening our understanding on the links between wood traits and demography during tree development.
Auteurs, date et publication :
Auteurs Andrés González-Melo , Juan Manuel Posada , Jacques Beauchêne , Romain Lehnebach , Sébastian Levionnois , Géraldine Derroire , Bruno Clair , Juliana Medeiros
Publication : AoB PLANTS
Date : 2024
Volume : 16
Issue : 1
Pages : plad090
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Maintaining a healthy gut microbiome plays a critical role in avoiding gut-related pathologies. Bacterial adherence to the intestinal epithelium plays a vital role in niche establishment in the gut, as in vitro experiments and mathematical modeling suggest that adherence provides a strong competitive advantage over free-floating planktonic microbes. Currently, we lack the ability to study gut microbiome adherence in an in vivo model system. Through sampling natural populations of Caenorhabditis, we discovered three bacterial species that adhere to the intestinal epithelium of several wild Caenorhabditis isolates. When transferred to C. elegans, all three bacterial species colonized the entire anterior to posterior length of the intestine lumen. We isolated these bacterial species via in vitro growth or selective enrichment in the nematode gut and identified them as Lelliottia jeotgali, Candidatus Lumenectis limosiae, and Candidatus Enterosymbion pterelaium, the latter two representing new species. Adherent Ca. L. limosiae negatively affects host fitness, while Lelliottia jeotgali and Ca. E. pterelaium exhibited a neutral effect in our assays. We demonstrated that two of these species can actively proliferate in the intestine throughout the host lifespan, with Lelliottia jeotgali colonizing throughout the lumen simultaneously and Candidatus Lumenectis limosiae showing anterior-to-posterior directionality. In competition assays, animals pre-colonized with L. jeotgali significantly reduced colonization by pathogenic Ca. L. limosiae, but this effect was not seen when animals were colonized by both bacteria simultaneously. Strikingly, regardless of the colonization paradigm, populations exposed to both bacteria showed a near-identical mitigation of the pathogenic effects of Ca. L. limosiae. Altogether, these strains illustrate the capacity of microbiome bacteria to adhere, replicate, and establish a niche across the entire intestinal lumen in C. elegans and they present an opportunity to study bacterial adherence in the context of a whole, intact and transparent animal.Competing Interest StatementThe authors have declared no competing interest.
Auteurs, date et publication :
Auteurs Dalaena E Rivera , Kayla Poirier , Samuel Moore , Ophélie Nicolle , Emily Morgan , Jonah-Faye Longares , Anupama Singh , Grégoire Michaux , Marie-Anne Félix , Robert J Luallen
Publication : bioRxiv
Date : 2024
Pages : 2024.10.24.620080
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Understanding the relative importance of biotic interactions, multiple environmental drivers, and neutral processes in shaping community diversity and composition is a central question for both theoretical and applied ecology.We analysed a dataset describing 125 earthworm communities sampled in 10 localities in French Guiana. DNA barcodes were used to delimit operational taxonomic units (OTUs) that we considered as species surrogates to avoid the taxonomic deficit and calculate community-scale species richness and pair-wise Sørensen beta-diversity. We used log-ratio and generalised linear models to highlight the effects of biotic interactions and environment as drivers of alpha diversity, and generalised dissimilarity models to figure out the relative contribution of space and environment to beta-diversity at different spatial extents.Community-scale alpha diversity was mainly explained by habitat filtering (soil texture) and interspecific competition that limit the number of locally co-existing species.Beta diversity between pairs of communities was mainly explained by distance when comparing communities in similar habitats, by topography and available soil phosphorus when comparing communities in different habitats, and by distance, elevation and climate when comparing all possible pairs of communities.While community composition is determined locally by neutral processes and environmental filtering, biogeographic processes linked to dispersal limitation and adaptation to local environment are the most influential on a regional scale. This highlights the complex interplay of dispersal limitation, biotic interactions and environmental filtering during the process of community assembly.Competing Interest StatementThe authors have declared no competing interest.
Auteurs, date et publication :
Auteurs Arnaud Goulpeau , Mickaël Hedde , Pierre Ganault , Emmanuel Lapied , Marie-Eugénie Maggia , Eric Marcon , Thibaud Decaëns
Publication : bioRxiv
Date : 2024
Pages : 2024.10.12.617983
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Northeastern South America has been historically undersampled across most biota. Surveys conducted for aquatic insects in French Guiana during the past 14 years have resulted in the collection of 16 species of Naucoridae, of which 10 are new country records. Of these 16 species, 10 are in the subfamily Ambrysinae, one in Ilyocorinae, and five in Limnocorinae. At least six of these species are considered rare, as very few specimens are known. A checklist, annotated list, distribution maps, and an illustrated key to identify adults of these species are presented.
Auteurs, date et publication :
Auteurs Robert W. Sites , Simon Clavier , William D. Shepard
Publication : Journal of the International Heteropterists' Society
Date : 2024
Volume : 1
Issue : 1
Pages : 33-56
Catégorie(s)
#CNRS #FORET NouraguesRésumé
The range of interactions between Cladosporium, a ubiquitous fungal genus, and insects, a class including about 60% of the animal species, is extremely diverse. The broad case history of antagonism and mutualism connecting Cladosporium and insects is reviewed in this paper based on the examination of the available literature. Certain strains establish direct interactions with pests or beneficial insects or indirectly influence them through their endophytic development in plants. Entomopathogenicity is often connected to the production of toxic secondary metabolites, although there is a case where these compounds have been reported to favor pollinator attraction, suggesting an important role in angiosperm reproduction. Other relationships include mycophagy, which, on the other hand, may reflect an ecological advantage for these extremely adaptable fungi using insects as carriers for spreading in the environment. Several Cladosporium species colonize insect structures, such as galleries of ambrosia beetles, leaf rolls of attelabid weevils and galls formed by cecidomyid midges, playing a still uncertain symbiotic role. Finally, the occurrence of Cladosporium in the gut of several insect species has intriguing implications for pest management, also considering that some strains have proven to be able to degrade insecticides. These interactions especially deserve further investigation to understand the impact of these fungi on pest control measures and strategies to preserve beneficial insects.
Auteurs, date et publication :
Auteurs Rosario Nicoletti , Elia Russo , Andrea Becchimanzi
Publication : Journal of Fungi
Date : 2024
Volume : 10
Issue : 1
Pages : 78