Institute of Ecology and Environmental Sciences IEES-Paris
Recent publications
Soil organic carbon (SOC) sequestration is the transfer of CO2 from the atmosphere into soil organic matter. It, therefore, relies on photo- synthesis and plant-derived carbon (C) input, which usually occurs through biomass production. Janzen et al. (2022) reminded us that when calculating SOC sequestration potential, we should recognise the source of C input to the soil as estimated by Net Primary Production (NPP). Indeed, increasing plant biomass production via NPP has been discussed as the most important driver of many SOC sequestration strategies (Soussana et al., 2019). Janzen et al. described a simple back-of-the-envelope calculation to demonstrate the limits of SOC stock increase as defined by the current NPP. While such a straightforward approach is reasonable to get a rough guestimate, it is important to recognise that there are limits to such a simplified modelling approach which carries significant uncertainties. In this comment, we discuss the limitations of such an approach and the way forward. Moreover, we show that Janzen et al.’s calculation con- tains inaccurate assumptions. When
Rapid synchronized seed germination is desirable to ensure seedling establishment and improve crop yield. However, abiotic stresses from drought, salinity, and heavy metals have a negative impact on seed germination. The application of silicon (Si) has emerged as a promising approach for improving seed germination, especially under unfavorable conditions. However, the mechanisms of Si action have not been systematically studied in germinating seeds under conditions of abiotic stress. Considering the potential importance of sustainable agriculture, here we review recent findings of how seeds of numerous species, including several important crops, respond to Si treatment under abiotic stress. Exogenous Si has multiple effects on embryo viability, reserve mobilization, hormone/enzyme activity, membrane integrity, antioxidant metabolism, and regulation of gene expression in seed germination.
Mutualistic co-evolution can be mediated by vertical transmission of symbionts between host generations. Organisms exhibit adaptations that ensure optimal microbial inheritance, yet it is unknown if this extends to superorganismal social insects that host co-evolved gut microbiomes. Here, we document consistent vertical transmission that preserves more than 80 bacterial genera across colony generations in a fungus-farming termite model system. Inheritance is governed by reproductives, analogous to organismal gametes, that found new colonies and are endowed with environmentally-sensitive and termite-specific gut microbes. These symbionts are then reliably passed on within the offspring colony, where priority effects dictate the composition of the forming colony microbiome. Founding reproductives thus play a central role in transmission. However, in sharp contrast to organismal inheritance of an endosymbiont within an egg, the multicellular properties of the superorganismal gametes allow for inheritance of entire communities of co-adapted microbes. Superorganismal inheritance aligns the reproductive interests of the host colony and a diverse set of microbes and clarifies a fundamental driver of millions of years of termite-bacterial co-diversification. Ultimately, the high symbiotic fidelity and host control favors mutualistic cooperation that should surpass that of other animals with complex microbiomes.
Blackcurrant juices and extracts containing anthocyanin may provide ergogenic benefits to sports performance. However, there are no studies examining the effects of coingestion of blackcurrant and caffeine. This investigation examined the effects of acute supplementation with a proprietary blackcurrant beverage administered in isolation or in combination with caffeine on repeated high-intensity cycling. Twelve well-trained male cyclists (mean ± SD : age, 39.5 ± 11.4 years; height, 177.9 ± 5.7 cm; weight, 78.2 ± 8.9 kg; and peak oxygen consumption, 4.71 ± 0.61 L/min) completed experimental sessions consisting of repeated (8 × 5 min) maximal intensity efforts. Four experimental treatments were administered in a double-blind, balanced Latin square design: blackcurrant + caffeine, blackcurrant + placebo, caffeine + placebo and placebo + placebo. Differences in power output, heart rate, oxygen consumption, muscle oxygen saturation, rate of perceived exertion, and cognitive function (Stroop) were compared between treatments using two-way repeated-measures analysis of variance and effect size analysis. There were no significant differences ( p > .05) in either physiological or cognitive variables with any supplement treatment (blackcurrant + caffeine, blackcurrant + placebo, and caffeine + placebo) relative to placebo + placebo. Moreover, any observed differences were deemed trivial ( d < 0.2) in magnitude. However, power output was lower ( p < .05) in blackcurrant + placebo compared with blackcurrant + caffeine. A blackcurrant extract beverage administered in isolation or combination with caffeine provided no beneficial effect on cycling performance or physiological measures relative to a placebo control.
The reproductive castes of eusocial insects are often characterized by extreme lifespans and reproductive output, indicating an absence of the fecundity/longevity trade-off. The role of DNA methylation in the regulation of caste- and age-specific gene expression in eusocial insects is controversial. While some studies find a clear link to caste formation in honeybees and ants, others find no correlation when replication is increased across independent colonies. Although recent studies have identified transcription patterns involved in the maintenance of high reproduction throughout the long lives of queens, the role of DNA methylation in the regulation of these genes is unknown. We carried out a comparative analysis of DNA methylation in the regulation of caste-specific transcription and its importance for the regulation of fertility and longevity in queens of the higher termite Macrotermes natalensis. We found evidence for significant, well-regulated changes in DNA methylation in mature compared to young queens, especially in several genes related to ageing and fecundity in mature queens. We also found a strong link between methylation and caste-specific alternative splicing. This study reveals a complex regulatory role of fat body DNA methylation both in the division of labour in termites, and during the reproductive maturation of queens.
Many organismal traits vary with body size, often reflecting trade-offs in the face of size-dependent constraints. For example, Haller's rule, the allometric pattern whereby smaller organisms have proportionally larger brains, can have carry-on effects on head design as the brain competes for space with other structures. Ant species with polymorphic worker castes are interesting cases for helping us understand these allometric effects. Here, we examine the effects of miniaturization on the ant power core, the mesosoma (thorax), with particular attention to how the scaling of nervous system structures affects the skeletomuscular elements involved with load bearing and locomotion. Using X-ray computed microtomography (microCT), we studied the thorax of Carebara perpusilla, an African ant species that has minute workers (1.5 mm-long) and larger soldiers (3.0 mm-long), allowing strong intraspecific comparisons. We find that the thoracic nervous system is relatively larger in minute workers, similar to Haller's rule, with consequences on the skeletomuscular organisation. Minute workers have relatively smaller petiole muscles and indirect head muscles, but relatively larger external trochanter muscles and direct head muscles. We link these allometric trade-offs to miniaturization and division of labor, and discuss how thorax design underlies the success of minute ants.
With current environmental changes, evolution can rescue declining populations, but what happens to their interacting species? Mutualistic interactions can help species sustain each other when their environment worsens. However, mutualism is often costly to maintain, and evolution might counter-select it when not profitable enough. We investigate how the evolution of the investment in a mutualistic interaction by a focal species affects the persistence of the system. Specifically, using eco-evolutionary dynamics, we study the evolution of the focal species investment in the mutualistic interaction of a focal species (e.g. plant attractiveness via flower or nectar production for pollinators or carbon exudate for mycorrhizal fungi), and how it is affected by the decline of the partner population with which it is interacting. We assume an allocation trade-off so that investment in the mutualistic interaction reduces the species intrinsic growth rate. First, we investigate how evolution changes species persistence, biomass production, and the intensity of the mutualistic interaction. We show that concave trade-offs allow evolutionary convergence to stable coexistence. We next assume an external disturbance that decreases the partner population by lowering its intrinsic growth rate. Such declines result in the evolution of lower investment of the focal species in the mutualistic interaction, which eventually leads to the extinction of the partner species. With asymmetric mutualism favouring the partner, the evolutionary disappearance of the mutualistic interaction is delayed. Our results suggest that evolution may account for the current collapse of some mutualistic systems like plant-pollinator ones, and that restoration attempts should be enforced early enough to prevent potential negative effects driven by evolution.
This study aimed to compare the chromosomal beta-lactamase from Pectobacterium versatile , PEC-1, with the well-known and globally distributed TEM-1 in terms of genetic and functional properties. Despite the similarities between the enzymes, we obtained no definitive proof of gene transfer for the emergence of bla PEC-1 from bla TEM-1 .
The wide host range phytopathogen D. dianthicola, first described in ornamentals in the1950s, rapidly became a threat for potato production in Europe and, more recently, worldwide. Previous genomic analyses, mainly of strains isolated from potato, revealed little sequence diversity. To further analyse D. dianthicola genomic diversity, we used a larger genome panel of 41 isolates encompassing more strains isolated from potato over a wide time scale and more strains isolated from other hosts. The phylogenetic and pan-genomic trees revealed a large cluster of highly related genomes but also the divergence of two more distant strains, IPO 256 and 67.19, isolated from potato and impatiens, respectively, and the clustering of the three strains isolated from Kalanchoe with one more distinct potato strain. An SNP-based minimal spanning tree highlighted both diverse clusters of (nearly) clonal strains and several strains scattered in the MST, irrespective of country or date of isolation, that differ by several thousand SNPs. This study reveals a higher diversity in D. dianthicola than previously described. It indicates the clonal spread of this pathogen over long distances, as suspected from worldwide seed trading, and possible multiple introductions of D. dianthicola from alternative sources of contaminations.
Aim Species shift their ranges as a consequence of climate change, hence modifying the structure of local assemblages. This may have important consequences for ecosystem functioning in the case of ecosystem engineers such as earthworms, especially when community restructuring leads to an alteration of their functional diversity. Here, we aimed to model the potential modification of the functional diversity of French earthworm assemblages in a context of climate change. Location Metropolitan France. Methods We fitted boosted regression trees to earthworm data collected using a standardized protocol across France in the 1960s. We used model projections constrained by a macroecological model of species richness to predict the composition of earthworm assemblages in the present and in two scenarios of climate change and two future time periods. We coupled these results with a large set of species traits to calculate predicted changes in functional diversity, which we summarized by ecoregion. Results Models predicted a clear decline in functional richness between the period of sampling and nowadays which are expected to continue in the future, with substantial differences depending on ecoregions and on whether species will be able to disperse or not. However, predicted changes in functional evenness and divergence are much weaker, suggesting that climate change will not affect all facets of functional diversity in the same way. Main Conclusions Our results mostly pointed to a potential reduction of the functional richness of earthworm communities in the future, but this predicted loss of diversity could be weaker if species are able to colonize new suitable sites or to persist in microclimate refugia. There are concerns, though, that these changes lead to an alteration of soil processes and of the ecosystem services they provide.
Phosphatidylinositol 4-kinases (PI4Ks) are the first enzymes that commit phosphatidylinositol into the phosphoinositide pathway. Here, we show that Arabidopsis thaliana seedlings deficient in PI4Kβ1 and β2 have several developmental defects including shorter roots and unfinished cytokinesis. The pi4kβ1β2 double mutant was insensitive to exogenous auxin concerning inhibition of root length and cell elongation; it also responded more slowly to gravistimulation. The pi4kß1ß2 root transcriptome displayed some similarities to a wild type plant response to auxin. Yet, not all the genes displayed such a constitutive auxin-like response. Besides, most assessed genes did not respond to exogenous auxin. This is consistent with data with the transcriptional reporter DR5-GUS. The content of bioactive auxin in the pi4kß1ß2 roots was similar to that in wild-type ones. Yet, an enhanced auxin-conjugating activity was detected and the auxin level reporter DII-VENUS did not respond to exogenous auxin in pi4kß1ß2 mutant. The mutant exhibited altered subcellular trafficking behavior including the trapping of PIN-FORMED 2 protein in rapidly moving vesicles. Bigger and less fragmented vacuoles were observed in pi4kß1ß2 roots when compared to the wild type. Furthermore, the actin filament web of the pi4kß1ß2 double mutant was less dense than in wild-type seedling roots, and less prone to rebuilding after treatment with latrunculin B. A mechanistic model is proposed in which an altered PI4K activity leads to actin filament disorganization, changes in vesicle trafficking, and altered auxin homeostasis and response resulting in a pleiotropic root phenotypes.
Species identification is currently a strong limitation to wild pollinator studies. It requires killing specimens for laboratory analyses, which can pose ethical issues in some programs of conservation biology and citizen science. The recent development of image-based identification tools using machine learning could challenge the current paradigm of required specimen euthanasia for species identification. However, to be accurate, these new methods call for standardized images or images of precise characters that are difficult or even impossible to obtain on live specimens. To facilitate the acquisition of these pictures, we tested two in-situ CO2 anesthesia protocols using material easily available, even in citizen science programs. We measured the time of anesthesia of 196 flower visitors belonging to the Hymenoptera and Diptera orders. The most efficient protocol enabled us to anesthetize 90 % of the specimens for more than a minute with a marginal mortality (1.5 %). Anesthesia time increased with specimen size in Hymenoptera and decreased with air temperature. Diptera were less sensitive to anesthesia. Further analyses would be required to investigate the potential sublethal effects of these anesthesia. These preliminary results suggest nonetheless that CO2-based anesthesia could help the development of non-lethal methods of wild pollinator identifications.
This paper proposes a contribution to tackle urban sanitation issues giving some hindsight on a place-based science-practice collaborative project. Insights from a French public service in charge of On-site Wastewater Treatment Systems (OWTS) highlighted the need to deepen the understanding of soil infiltration assessments and to clarify their relation to some misunderstandings between actors. The initial aim was to explore how a knowledge based approach can offer an original perspective to historical “septic tanks ”and overcome technical and organizational difficulties. In this work we consider OWTS as hybrid infrastructures necessary to collect, transport, treat and dispose of domestic wastewater on the plot where it is generated. We suppose that OWTS adaptive management (sludge not included) offer many opportunities regarding water circulation (ecological function), infrastructure diversity (redundancy), and soil-based decision making (spatial planning). The main objective of this paper is to document the French sociotechnical configuration through the interplay between soil and water actors, OWTS technics and local institutions. The originality is to look at OWTS through the lens systemic perspective of Nature-Based Solutions (NBS). We first contextualize OWTS implementation and plan- ning by presenting technical design studies (water-soil interactions, indicators assessment) and the diversity and capacity of actors. Second, we build on the application of a soil-based methodology in a peri-urban district to pro- vide a place-based outlook on the influence of soil infiltration rates variability in day-to-day management. While the current consideration given to soil infiltration rate in OWTS design studies created a situation of conflicts and contestations between actors, a sociotechnical transition is taking place with new regulations and innova- tive energy-driven device. Moreover, collective infrastructure for domestic wastewater is currently challenged by densification constraints in metropolitan areas (urban sprawl regulation). As a consequence, resolving binding measures for indicators assessment would support OWTS integration into mainstream urban development. Care- ful investigation of soil hydraulic functions is thus a steppingstone in the search for an adaptive strategy both at the plot and the neighborhood scales. Not only OWTS are opportunities to support the adaptive management process in the water sector, but OWTS have also the potential to improve soil-based decision-making in urban areas. Finally, valuating OWTS as useful NBS for wastewater management in urban areas supports the evalua- tion of soil capacities to deliver ecosystem services and contributes to justify land-use changes on a functional knowledge basis.
The Indian jumping ant Harpegnathos saltator is one of the most well-studied ant species; however, little is known about the biology and behavior of sister species in the genus. To understand the universality of the phenomena revealed in H. saltator, biological studies of closely related species are important. We investigated the nest architecture and colony reproductive structure of Harpegnathos venator at two sites in northern Thailand. Nests had chimney-like entrances with a funnel diameter of about 3 cm and consisted of two or three chambers, the floors of which were flat and smooth. The floors and walls inside the chambers were decorated with several small fragments of cocoons, which has been referred to as “wall-papering”. Most colonies included one or more mated dealate queens that laid eggs, whereas only a few mated workers reproduced in the queenright colonies. In our sampling, virgin dealate queens were found in several colonies, but there were very few queenless colonies that reproduced by mated workers. Additional colonies collected from three other sites in Thailand also had dealate queens. The H. venator colonies reproduced mainly by mated queens, although many mated workers were present. The nest architecture of H. venator was similar to that of H. saltator, but the colony reproductive structure was different: queen colonies of H. saltator are always monogynous, and queenless colonies that reproduce by gamergates are frequently found. Furthermore, virgin dealate queens are never found in H. saltator. Factors affecting these differences between the two congeneric species are discussed.
Urban areas often host exotic plant species, whether managed or spontaneous. These plants are suspected of affecting pollinator diversity and the structure of pollination networks. However, in dense cityscapes, exotic plants also provide additional flower resources during periods of scarcity, and the consequences for the seasonal dynamics of networks still need to be investigated. For two consecutive years, we monitored monthly plant-pollinator networks in twelve greenspaces of Paris, France. We focused on seasonal variations in the availability and attractiveness of flower resources, comparing native and exotic plants at both the species and community levels. We also considered their respective contributions to networks properties over time (specialization and nestedness). Exotic plants provided more abundant and diverse flower resources than native plants, especially late in the season. However, native plants received more visits and attracted more pollinator species, both at the community and species levels. Exotic plants were involved in more generalist interactions, and this became more so as the season progressed. In addition, they contributed more to network nestedness than native plants. These results show that exotic plants are major components of plant-pollinator interactions in a dense urban landscape, even though they are less attractive to diverse pollinators. They constitute a core of generalist interactions that increase nestedness and can participate in the overall stability of the network. However, most exotic species were seldom visited by insects. Pollinator communities may benefit from including more native species, as well as entomophilous varieties of exotic plants, when managing urban greenspaces.
A recent study showed that, in the ant Temnothorax nylanderi, city colonies are more tolerant to cadmium than forest colonies. However, because of annual variation in biological factors (e.g. body size, anti-stress protein production or trace metal accumulation rate), trace metal tolerance may vary over the year. We aimed at testing whether tolerance to cadmium of colonies of T. nylanderi differs between two different seasons within the same year (winter and spring). We also assessed whether the better cadmium tolerance of city colonies was constant over these two different time points. We collected colonies at the end of their hibernation period (winter colonies) and several weeks after (spring colonies) from two different habitats (forest and city) to assess whether response to cadmium was consistent regardless of the environment. We exposed colonies to a cadmium or a control treatment for 61 days. We compared tolerance to cadmium between spring/winter and city/forest colonies by measuring several life history traits. We found that spring colonies tolerates cadmium better than winter colonies, and that city colonies have a higher tolerance to cadmium but only in spring. Although further studies with replicated pairs of city/forest habitats and different years will be necessary to confirm those results, our study suggests that tolerance to trace metals can fluctuate along the yearly cycle.
ContextWind erosion plays a major role in land degradation in semi-arid areas, especially in the Sahel. There, wind erosion is as sensitive to land use and land management as to climate factors. Future land use intensification may increase wind erosion and induce regional land degradation.Objective We aimed to estimate wind erosion responses to changing land management in a Sahelian region.Methods We defined land use intensification scenarios for a study site in southwestern Niger for two historical situations (1950s and 1990s), and two alternative prospective scenarios (2030s: extensive or intensive). We simulated vegetation growth and horizontal sediment flux of wind erosion for the corresponding landscapes.ResultsAnnual amounts of horizontal sediment flux increased with land management changes from 1950s (nil flux) to 1990s (176 kg m−1 yr−1) and 2030s (452 to 520 kg m−1 yr−1), mostly because of differences in land use, declining soil fertility, and practices decreasing the dry vegetation. For 2030s, intensive scenario exhibited larger vegetation yields than extensive conditions, but similar large values of horizontal sediment flux, thus questioning the sustainability of both scenarios. Realistic sets of practices had as large an influence as the largest theoretical range of practices on the variability of annual horizontal sediment flux. This variability was as large as that due to meteorological conditions.Conclusions This study demonstrates that the environmental impact of land use and management practices, of which wind erosion is an aspect, must be assessed at the landscape scale to account for the variability in land cover and associated land management.
Tracer addition experiments, particularly using isotopic tracers, are becoming increasingly important in a variety of studies aiming at characterizing the flows of molecules or nutrients at different levels of biological organization, from the cellular and tissue levels, to the organismal and ecosystem levels. However, performing rigorous statistical analyses to gain reliable quantitative insights from these experiments often remains challenging. We present an approach based on Hidden Markov Models (HMM) to estimate nutrient flow parameters across a network, and its implementation in the R package isotracer. The isotracer package is capable of handling a variety of tracer study designs, including continuous tracer drips, pulse experiments, and pulse‐chase experiments. It can also take into account tracer decay when radioactive isotopes are used. To illustrate its use, we present three case studies based on published data and spanning different levels of biological organization: a molecular‐level study of protein synthesis and degradation in Arabidopsis thaliana, an organismal‐level study of phosphorus incorporation in the eelgrass Zostera marina, and an ecosystem‐level study of nitrogen dynamics in Trinidadian montane streams. With these case studies, we illustrate how isotracer can be used to estimate uptake rates, turnover rates, and total flows, as well as their uncertainty. We also show how to perform model selection to compare alternative hypotheses. The isotracer package allows researchers from a broad range of disciplines to fully take advantage of their datasets through rigorous statistical analyses. We conclude by discussing isotracer's further applications, limitations, and possible future improvements and expansions.
Kings and queens of eusocial termites can live for decades, while queens sustain a nearly maximal fertility. To investigate the molecular mechanisms underlying their long lifespan, we carried out transcriptomics, lipidomics and metabolomics in Macrotermes natalensis on sterile short-lived workers, long-lived kings and five stages spanning twenty years of adult queen maturation. Reproductives share gene expression differences from workers in agreement with a reduction of several aging-related processes, involving upregulation of DNA damage repair and mitochondrial functions. Anti-oxidant gene expression is downregulated, while peroxidability of membranes in queens decreases. Against expectations, we observed an upregulated gene expression in fat bodies of reproductives of several components of the IIS pathway, including an insulin-like peptide, Ilp9. This pattern does not lead to deleterious fat storage in physogastric queens, while simple sugars dominate in their hemolymph and large amounts of resources are allocated towards oogenesis. Our findings support the notion that all processes causing aging need to be addressed simultaneously in order to prevent it.
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59 members
Adrien Perrard
  • Community Diversity and Ecosystem Functioning
Isabelle Gounand
  • Community Diversity and Ecosystem Functioning
Thomas Lerch
  • Community Diversity and Ecosystem Functioning
Sébastien Barot
  • Community Diversity and Ecosystem Functioning
Juliette Leymarie
  • Vegetal Sciences
Paris, France