Biology subjects

Plantegenest, M.

Publications and source records attributed to Plantegenest, M..

4 recordsLinked to original sources

bioRxiv2025

Healthy soils, rising pests? Stopping plowing improves soil quality but increases wireworm infestation: evidence from a long-term field study

Conventional tillage (i.e. plowing) is often associated with soil degradation and a loss of biodiversity. In response, reduced tillage has increasingly been promoted as a sustainable alternative for its positive impacts on soil structure, water dynamics, and biodiversity. However, reduced tillage not only favors beneficial soil-dwelling organisms, but also pests. In this field study, we examined the effects of five years of reduced tillage on the physical properties of the soil and the dynamics of Agriotes wireworm populations (Elateridae), which are increasingly widespread pests. Our results show that tillage reduction led to stable edaphic conditions and a redistribution of organic matter, creating a favorable environment for wireworms. While our results demonstrate the beneficial effects of reduced tillage on aggregate stability, they also indicate a concomitant increase in soil bulk density, suggesting a reduction in water-holding capacity. Monitoring of wireworm populations revealed their aggregated distribution and their increase in abundance in infested areas year on year. Monitoring soil moisture revealed that tillage reduction improved water dynamics, enhancing infiltration and reducing evaporation. This could potentially favor the development of wireworms. Surprisingly, wireworm size distribution showed a higher proportion of young instars in plowed plots, evidencing that, firstly, the lack of soil cover does not prevent oviposition and that injury caused by plowing targets more the last instars rather than young larvae. While reduced tillage improves key soil health indicators, our findings suggest a potential trade-off in terms of increased pest pressure. Our study highlights the importance of adopting a holistic approach when designing sustainable cropping systems, as well as considering the services and dis-services they provide.

ecology↗

bioRxiv2024

Unveiling the Hidden Feast: translating molecular detection into predation rate. An example on biological control by generalist predators in agricultural fields.

Very few processes are as decisive as predation in shaping the structure and dynamics of ecological communities. For most predator species, the number of prey items killed by a predator in a day (predation rate) remains impossible to assess because direct observations are scarce or impossible to acquire. To fill this gap, we propose here a Hierarchical Bayesian Model that integrates data on the molecular detection of prey in predators (e.g. PCR results), on individuals captured in the field on the one hand, and on individuals fed in the laboratory, on the other, in a novel mechanistic framework. By explicitly combining the processes of predation and digestion, model fit provides an estimate of the slope and intercept of the digestion curve, and an estimate of the number of prey consumed by a predator in a day. In a case study targeting 25 carabid beetle species and 5 types of prey in agricultural fields (winter wheat), we use our model to estimate predation rates at species and community scales and demonstrate its advantages for studies on biocontrol and beyond. Code and Data are available on this repository : /r/HBM_PredationCode-C725/

ecology↗

bioRxiv2018

DNA metabarcoding diet analysis reveals dynamic feeding behaviour and biological control potential of carabid farmland communities

Maximizing the delivery of key ecosystem services such as biological control through the management of natural enemy communities is one of the major challenges for modern agriculture. The main obstacle lies in our yet limited capacity of identifying the factors that drive the dynamics of trophic interactions within multi-species assemblages. Invertebrate generalist predators like carabid beetles are known for their dynamic feeding behaviour. Yet, at what extent different carabid species contribute to the regulation of animal and plant pests within agroecosystems is currently unknown. Here, we developed a DNA metabarcoding approach for characterizing the full diet spectrum of a community of fourteen very common carabid species inhabiting an intensively managed Western-European agroecosystem. We then investigated how diet and biological control potential within the carabid community varies with the sampling field location and the crop type (wheat vs oilseed rape). DNA metabarcoding diet analysis allowed to detect a wide variety of animal and plant taxa from carabid gut contents thus confirming their generalist feeding behaviour. The most common prey categories detected were arachnids, insects, earthworms and several plant families potentially including many weed species. Our results also show that the field location and the crop type are much stronger determinants then the species regarding carabid dietary choice: significantly more trophic links involving dipteran prey were observed in wheat, whereas more collembolan and plant prey was consumed in oilseed rape by the same carabid community. We speculate that structural differences in the habitats provided by these two crop types drive differences in resource availability cascading up the trophic chain, and we assume that specific carabid taxa could hardly be used to infer levels of ecosystem services (biological control) or disservices (e.g. intraguild predation). However, as this is the first study to report the use of DNA metabarcoding diet analysis in predatory carabid beetles we urge caution over the interpretation of our results. For instance, overall detection rates were rather low (31% of the individuals analysed tested positive for at least one prey category) most likely due to the overwhelming amplification of the carabid host DNA. Therefore, we acknowledge that more studies are required in order to confirm our observations and conclude with few recommendations for further improvements of the community-level DNA metabarcoding analysis of carabid diet.

ecology↗

bioRxiv2017

Comparing three types of dietary samples for prey DNA decay in an insect generalist predator

The rapidly growing field of molecular diet analysis is becoming increasingly popular among ecologists, especially when investigating methodologically challenging groups such as invertebrate generalist predators. Prey DNA detection success is known to be affected by multiple factors, however the type of dietary sample has rarely been considered. Here, we address this knowledge gap by comparing prey DNA detection success from three types of dietary samples. In a controlled feeding experiment, using the carabid beetle Pterostichus melanarius as a model predator, we collected regurgitates, feces and whole consumers (including their gut contents) at different time points post-feeding. All dietary samples were analyzed using multiplex PCR targeting three different length DNA fragments (128 bp, 332 bp and 612 bp). Our results show that both the type of dietary sample and the size of the DNA fragment contribute to a significant part of the variation found in the detectability of prey DNA. Specifically, we observed that in both regurgitates and whole consumers prey DNA was detectable significantly longer for all fragment sizes than for feces. Based on these observations, we conclude that prey DNA detected from regurgitates and whole consumers DNA extracts are comparable, whereas prey DNA detected from feces, though still sufficiently reliable for ecological studies, will not be directly comparable to the former. Therefore, regurgitates and feces constitute an interesting, non-lethal source for dietary information that could be applied to field studies in situations when invertebrate predators should not be killed.

ecology↗