Biology subjects

Mouchet, M.

Publications and source records attributed to Mouchet, M..

4 recordsLinked to original sources

bioRxiv2025

Biodiversity temporal trends are reshaping food web structure and redundancy in riverine ecosystems

Biodiversity temporal changes are expected to profoundly impact ecosystem functioning and stability, yet large-scale empirical evidence remains limited. Bridging this gap requires aligning biodiversity temporal trends with food web theory and Biodiversity-Ecosystem Functioning research, both of which provide strong predictions about the ecological consequences of biodiversity loss. Most insights on those consequences currently rely on spatial comparisons of ecological communities, assuming they reflect temporal trends--a space-for-time substitution. Here, we analyze biodiversity and food web time series from over 400 riverine fish communities across France (1995-2018) to evaluate how biodiversity temporal trends reshape food web structure and community functioning. We examine relationships among species richness, community biomass, and three key food web metrics: connectance, weighted average trophic level, and trophic pathway redundancy. We also test the space-for-time hypothesis using spatial gradients and a theoretical food web model. Our structural equation models and robustness analysis reveal that declines in species richness strongly correlate with reduced community biomass, with top trophic-level species playing a disproportionate role in food web changes. Declining biomass is associated with the loss of top trophic levels and decreased connectance, while temporal changes in species richness negatively correlates with changes in connectance. Both biomass and species richness declines reduce trophic pathway redundancy, suggesting that biodiversity loss weakens community robustness to future perturbations. Our findings align with food web theory and Biodiversity-Ecosystem Functioning research, support the validity of space-for-time approaches for basic food web metrics, and demonstrate the relevance of food web metrics as indicators of ecosystem function and fragility. SignificanceRates of biodiversity loss raise urgent concerns about ecosystem functioning and stability, yet how biodiversity trends directly impact these critical processes remains unclear. For instance, food web & Biodiversity-Ecosystem Functioning research has delivered strong predictions about the ecological consequences of biodiversity loss but lack of empirical assessment. Using an extensive dataset of riverine fish communities, we link biodiversity trends to temporal changes in food web structure. We demonstrate that temporal changes in species richness and community biomass consistently associate with altered food web structure. We found that declining biodiversity reduces trophic pathway redundancy, likely increasing ecosystem vulnerability to perturbations. Our findings suggest that food web structure metrics could serve as valuable indicators for monitoring ecosystem health and guiding conservation strategies.

ecology↗

bioRxiv2020

Promising potential of high-throughput molecular phenotyping of freshwater fishes for environmental assessment

The recent democratization of high-throughput molecular phenotyping allows the rapid expansion of promising untargeted multi-dimensional approaches (e.g. epigenomics, transcriptomics, proteomics, metabolomics, ...). Indeed, these emerging omics tools, processed for ecologically relevant species, may present innovative perspectives for environmental assessments, that could provide early warning of eco(toxico)logical impairs. In a previous pilot study (Sotton et al., Chemosphere 2019), we explore by 1H NMR the bio-indicative potential of metabolomics analyses on the liver of 2 sentinel fish species (Perca fluviatilis and Lepomis gibbosus) collected in 8 water bodies of the peri-urban Paris area (France). In the present study, we further investigate on the same samples the great potential of high-throughput UHPLC-HRMS/MS analyses. We show that the LC-MS metabolome remarkably allows clear separation of individuals according to the species, but also according to their respective sampling lakes. Interestingly, similar variations of Perca and Lepomis metabolomes occur locally indicating that site-specific environmental constraints drive the metabolome variations beyond the obvious genetic differences between the two species, and seem to be influenced by the production of noxious metabolites by cyanobacterial blooms in certain lakes. Thus, the development of such reliable environmental metabolomics approaches is constituting an innovative bio-indicative tool for ecological stress assessment, such as toxigenic cyanobacterial blooms, and aim at being further follow up.

ecology↗

bioRxiv2019

On islands, evolutionary but not functional originality is rare

Functionally and evolutionary original species are those whose traits or evolutionary history are shared by few others in a given set. These original species promote ecosystem multifunctionality, the ability to cope with an uncertain future, future benefits to society and therefore have a high conservation value. A potential signal of their extinction risks is their rarity (stating for geographic range-restriction in this study). On islands, life in isolation conducted to the rise of a multitude of original forms and functions as well as to high rates of endemism. Not only patterns and processes of insular originality are unexplained but the relationship between originality and rarity is still unknown. The aim of this study is to assess how original insular species are, to explore whether original species are rare or not and to investigate the factors that may explain the rarity of original species. We first compared the functional and evolutionary originality of monocotyledon species and whether continental or insular species were more original. We found that species restricted to islands were more original than continental species and, although functionally and evolutionary original species were dissimilar, many occurred on similar territories so that regional conservation strategies may allow to conserve these distinct forms. Yet, evolutionary original species were significantly more range-restricted than those which were distinct in their traits. Reflecting their rarity, evolutionary original species had low dispersal abilities and were found on islands where settlement may have been facilitated. On the opposite, functionally original species could reach a wider set of islands by being transported on long-distances. While some mechanisms may both explain rarity and originality such as extinctions, others may be specific to each of these biodiversity facets, in particular diversification, niche shift and expansion, and dispersal power. Implications for conservation are huge: original species are range-restricted and mostly found in the most threatened systems of the world, i.e. islands, endangering the reservoir of features against an uncertain future.

ecology↗

bioRxiv2019

Tracking the origin of island diversity: insights from divergence with the continental pool in monocots

At their early age, a large proportion of island pools were a partial sampling of mainland pools whatever islands are oceanic or fragments of the mainland. Through time, colonization, diversification, extinctions, have deeply transformed insular and continental communities and therefore the degree to which they share species. We studied the relative importance of these mechanisms by looking at the shared evolutionary history between species pools on islands and continents. Indeed, most of these mechanisms are not neutral regarding phylogeny but are linked to species evolutionary relationships. We measured the phylogenetic divergence between continental and insular monocot communities through metrics of beta Mean Pairwise Distance and beta Mean Nearest Taxon Distance. We first tested the influence of spatial and environmental distance to the continent, two main factors of divergence, but whose explanatory power in a phylogenetic context was still unclear. We showed that both dispersal and enviromental filtering were important to explain divergence, although species that could pass these filters were not phylogenetically clustered. There was however a clear distinction between oceanic and continental islands: a stable climate in the latters was key to the survival of the original biota leading to a high proportion of shared lineages between the mainland and islands. But distance to the continent was only part of the story, we investigated additionnal mechanisms of phylogenetic divergence through their relation to island features and community structure. This showed that the most divergent islands occurred in the tropics and that processes of persistence of original species, diversification in remote archipelagos, neutral colonization on easy-to-reach islands, turnover, and high speciation rates may have driven phylogenetic divergence at a world scale. This study showed how phylogenetic approaches may explain how divergence, or similarity may have arisen and provide new insights in the continental origin of plant diversity on islands.

ecology↗