Thomas Enriquez, PhD - Past researches

2016-2019: PhD student, CNRS – UMR ECOBIO, University of Rennes 1 (France). Supervisors : Dr. Hervé Colinet & Dr. Maryvonne Charrier

Topic:
Study of the underlying physiological mechanisms of thermal tolerance plasticity in the invasive fly Drosophila suzukii.

Summary:

Drosophila suzukii is an invasive pest in Europe, North and South America. Unlike other drosophilids, females oviposit in ripe fruits that larvae consume, provoking important damages on fruit productions. The overwintering strategies of this fly are yet poorly understood. Therefore, the aim of my thesis was to acquire new fundamental knowledge about the thermal biology of this fly, and more specifically the plasticity of its thermal tolerance and the physiological mechanisms underpinning cold acclimation. In order to define its basal thermal tolerance, adults and pupae were subjected to a large set of high and low temperatures. My data confirmed that this pest was chill susceptible, and showed that survival was greatly compromised during exposures above 32°C. Next, I evaluated its thermal tolerance plasticity. My data confirmed the high plasticity of its cold tolerance, as fluctuating thermal regimes and acclimation were able to decrease the mortality due to cold exposures. Acclimation in this species was correlate with several physiological adjustments, such as: cryoprotectant accumulation, remodeling of membrane phospholipids and lipidic reserves, upregulation of genes linked with activity of ionic transporters and maintenance of metabolic homeostasis. Those modifications (which are shared among temperate insect species) are likely linked with cold tolerance increase provoked by acclimation. Therefore, these physiological adjustments could play an important role in its overwintering success in Europe and Canada, which can facilitate its invasion in these regions. These new data will participate to a better understanding of its physiological limits, and are thus of importance for predicting the evolution of its invasion front and its phenology and demographic variations in invaded areas. My results are also of interest regarding the set-up of integrated pest management strategies against this fly.

2015: MSc2 student, INRA PACA –Biocontrol Laboratory (Antibes, France). Supervisor : Dr. Elisabeth Tabone

Topic:
Utilization of trichogramma wasps to set up biocontrol strategies against the box tree moth Cydalima perspectalis.

Summary:
The box-tree moth Cydalima perspectalis is a specialized pest of box-trees. The damage it causes to box-trees have an important economic and ecological impact. As part of the SaveBuxus project, the Biocontrole laboratory (INRA UEFM) is working to develop a biological control strategy using Trichogramma parasitoid wasps. This study was diviided in three main parts. First, 54 Trichogramma strains were tested on C. perspectalis eggs. Three French strains that were more effective at succesfully parasitizing the moth eggs were identified (P generation). Secondly, I evaluated the quality of the emerging females from the C. perspectalis parasitized eggs (F1 generation). 30% of the F1 population was bigger and seemed to be more effective in killing C. perspectalis eggs than the P. Thirdly, I focused on Trichogramma female behaviours. Previous studies have shown intraspecific variability of the efficacy of Trichogramma females on C. perspectalis. I investigated the origins of this variability by observing female behaviours. I observed that ovipositor insertion in moth's egg by wasp female was not necessarily linked with succesfull parasitism, but still often lead to the death of the host egg.

2014 & 2013: Internship in agroecology, François Rabelais University – CETU INNOPHYT (Tours, France). Supervisors : Ingrid Arnault & Maxime Cornillon

Topics:

Protocol implementation for monitoring the dispersion of carabid beetles in agroforestry fields.
Study of the entomofauna biodiversity in the city of Tours.

Summary:
Agroforestry (typically, inserting tree strips in crop fields) sounds like a promising avenue to increase biodiversity in agricultural landscapes. Plants association in agroforestry are beneficial for insect richness. Some of these species can be beneficial for crop protection, as they predate on pests. Our work focused on a specific kind of auxiliary insects, carabid beetles, which are abundant in cultural landscapes. However, how they can move and disperse between, or inside agroforestry’s tree strips is still unknown. Our aim was to set up a protocol allowing to track those movements. In this project, we first evaluated biodiversity richness in 2 agroforestry fields, and second aimed to estimate distance traveled by carabid beetle species that were the most abundant in these fields. Our results revealed 2 prevalent “key” species: Poecilus cupreus, an aphid predator, and Carabus auratus, a slug and snail predator. Attempt to track the movement and use of the landscape by these two species was done using a harmonic radar