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The lab studies the conditions for the installation and the evolution of introduced populations of insects. Our biological models are invasive pests and species used in biological control. Our research on introductions, subsequent demographic and geographic expansions, and the associated evolutive phenomena, is based on ecology and evolutionary biology. We combine behavioural ecology, population genetics and   population dynamics.

Recent Publications               

• Lartigue Silène, Myriam Yalaoui, Jean Belliard, Claire Caravel, Louise Jeandroz, Géraldine Groussier, Vincent Calcagno, Philippe Louâpre, François Xavier Dechaume-Moncharmont, Thibaut Malausa, and Jérôme Moreau (2022) Consistent Variations in Personality Traits and Their Potential for Genetic Improvement in Biocontrol Agents: Trichogramma Evanescens as a Case Study. Evolutionary Applications (Feb):1–15.
• Jacquet Florence, Marie Hélène Jeuffroy, Julia Jouan, Edith Le Cadre, Isabelle Litrico, Thibaut Malausa, Xavier Reboud, and Christian Huyghe (2022) Pesticide-Free Agriculture as a New Paradigm for Research. Agronomy for Sustainable Development 42(1):1–24.
• Morel-Journel, Thibaut, Marjorie Haond, Laurent Lamy, David Muru, Lionel Roques, Ludovic Mailleret, and Elodie Vercken (2022) When Expansion Stalls: An Extension to the Concept of Range Pinning in Ecology. Ecography 2022(2):1–10.
• Scotta Michela Ion, Lucas Margris, Nadine Sellier, Sylvie Warot, Flavio Gatti, Fabio Siccardi, Patricia Gibert, Elodie Vercken, and Nicolas Ris (2021) Genetic Variability, Population Differentiation, and Correlations for Thermal Tolerance Indices in the Minute Wasp, Trichogramma Cacoeciae. Insects 12(11).
• Pasquier Antoine, Lucie S. Monticelli, Adeline Moreau, Benjamin Kaltenbach, Candice Chabot, Thibault Andrieux, Maxime Ferrero, and Elodie Vercken (2021) A Promising Predator-in-First Strategy to Control Western Corn Rootworm Population in Maize Fields. Agronomy 11(10):1–16.
• Coates Brad S., Emeline Deleury, Aaron J. Gassmann, Bruce E. Hibbard, Lance J. Meinke, Nicholas J. Miller, Jennifer Petzold-Maxwell, B. Wade French, Thomas W. Sappington, Blair D. Siegfried, and Thomas Guillemaud (2021) Up-Regulation of Apoptotic- and Cell Survival-Related Gene Pathways Following Exposures of Western Corn Rootworm to B. Thuringiensis Crystalline Pesticidal Proteins in Transgenic Maize Roots. BMC Genomics 22(1):1–27.
• Collin François-David, Ghislain Durif, Louis Raynal, Eric Lombaert, Mathieu Gautier, Renaud Vitalis, Jean-Michel Marin, and Arnaud Estoup (2021) Extending Approximate Bayesian Computation with Supervised Machine Learning to Infer Demographic History from Genetic Polymorphisms Using DIYABC Random Forest. Molecular Ecology Resources 21:2598–2613.
• Pacheco da Silva, V.C., Aquino, D.A., Crochard, D., Malausa, T., Botton, M., and Palero, F. (2021) Parasitoids (Hymenoptera) of Mealybug Pests (Hemiptera: Pseudococcidae) from Southern Brazil: Molecular and Morphological Characterization. Neotropical Entomology 50, 759–766. https://doi.org/10.1007/s13744-020-00841-3
• Dahirel Maxime, Aline Bertin, Vincent Calcagno, Camille Duraj, Simon Fellous, Géraldine Groussier, Eric Lombaert, Ludovic Mailleret, Anaël Marchand, and Elodie Vercken (2021) Landscape Connectivity Alters the Evolution of Density- Dependent Dispersal during Pushed Range Expansions. BioRxiv 1–26.
• Mallez Sophie, Chantal Castagnone, Eric Lombaert, Philippe Castagnone-sereno, and Thomas Guillemaud (2021) Inference of the Worldwide Invasion Routes of the Pinewood Nematode Bursaphelenchus Xylophilus Using Approximate Bayesian Computation Analysis. Peer Community Journal 1:e56.
• Dahirel Maxime, Aline Bertin, Marjorie Haond, Aurélie Blin, Eric Lombaert, Vincent Calcagno, Simon Fellous, Ludovic Mailleret, Thibaut Malausa, and Elodie Vercken (2021) Shifts from Pulled to Pushed Range Expansions Caused by Reduction of Landscape Connectivity. Oikos 130(5):708–24.
• Collet M, Amat I, Sauzet S, Auguste A, Fauvergue X, Mouton L, Desouhant E (2020) Insects and incest: Sib-mating tolerance in natural populations of a parasitoid wasp. Molecular Ecology, 29, 596-609. https://doi.org/10.1111/mec.15340
• Dahirel M, Bertin A, Haond M, Blin A, Lombaert E, Calcagno V, Fellous S, Mailleret L, Vercken E (2020) Shifts from pulled to pushed range expansions caused by reductions in connectedness. bioRxiv. https://doi.org/10.1101/2020.05.13.092775
• Guadalupe A-G, Lombaert E, Mariano O, Rubén P-I, Karina B, Domínguez CA, Juan F (2020) Local dispersal pathways during the invasion of the cactus moth, Cactoblastis cactorum, within North America and the Caribbean. Scientific Reports, 10. https://doi.org/10.1038/s41598-020-66864-3
• Muru D, Borowiec N, Thaon M, Ris N, Madalina VI, Sylvie W, Vercken E (2020) The open bar is closed: restructuration of a native parasitoid community following successful control of an invasive pest. bioRxiv, 2019-12. https://doi.org/10.1101/2019.12.20.88490

Recent results

When expansion stalls: an extension to the concept of range pinning in ecology

Identifying  the  factors  modulating  range  expansion  is  essential  to  accurately  predict  changes in the spatial distribution of populations. By preventing population growth after dispersal, Allee effects can lead to front stops in discrete space, called ’pinning’ if permanent. However, other mechanisms, such as positive density-dependent dispersal, have also been shown to affect the rate of range expansion and generate discrete-space front stops, albeit temporarily. In this study, we investigated the stability of the front stops generated by such mechanisms in relation to the carrying capacity of the envi-ronment. To this end, we performed artificial range expansions in discrete space using stochastic  simulations  and  microcosm  experiments.  Simulation  results  confirmed  that  density-dependent  dispersal  alone  can  generate  sustained  front  stops,  albeit  for  a limited range of carrying capacities. We also highlighted the synergy between Allee effects and density-dependent dispersal on pinning emergence. Experimental results, obtained  using  a  model  species  known  to  exhibit  density-dependent  dispersal,  but  without Allee effects, confirmed the model results. Furthermore, our study raises the issue of carefully considering the conditions for pinning stability, in a stochastic con-text and depending on the time-scale considered.

Consistent variations in personality traits and their potential for genetic improvement in biocontrol agents: Trichogramma evanescens as a case study

Improvements in the biological control of agricultural pests require improvements in the phenotyping methods used by practitioners to select efficient biological control agent (BCA) populations in industrial rearing or field conditions. Consistent inter-individual variations in behaviour (i.e. animal personality) probably affect BCA efficiency, but have never been taken into account in the development of phenotyping methods, despite having characteristics useful for phenotyping: repeatable (by definition), often heritable, etc. We developed a video-tracking method targeting animal personality traits and evaluated the feasibility of its use for genetic improvement in the BCA Trichogramma evanescens, by phenotyping 1,049 individuals from 24 isogenic lines. We found consistent individual variations in boldness, activity and exploration. Personality differences between the 24 isogenic lines suggested a genetic origin of the variations in activity and exploration (broad-sense heritability estimates of 0.06 to 0.11) and revealed a trade-off between exploration and fecundity.

Inference of the worldwide invasion routes of the pinewood nematode Bursaphelenchus xylophilus using approximate Bayesian computation analysis

Population genetics have been greatly beneficial to improve knowledge about biologi- cal invasions. Model-based genetic inference methods, such as approximate Bayesian computation (ABC), have brought this improvement to a higher level and are now es- sential tools to decipher the invasion routes of any invasive species. In this paper, we performed ABC random forest analyses to shed light on the pinewood nematode (PWN) worldwide invasion routes and to identify the source of European populations. Originat- ing from North America, this microscopic worm has been invading Asia since 1905 and Europe since 1999, causing tremendous damage on pine forests. Using microsatellite data, we demonstrated the existence of multiple introduction events in Japan (at least two involving individuals originating from the USA) and China (one involving individuals originating from the USA and one involving individuals originating from Japan). We also found that Portuguese samples had a Japanese origin. We observed some discrepancies between descriptive genetic methods and the ABC method, which are worth investigat- ing and are discussed here. The ABC method helped clarify the worldwide history of the PWN invasion, even though the results still need to be considered with some caution because the features of the PWN and the genetic markers used probably push the ABC method to its very limits.

The highs and lows of dispersal: how connectivity and initial population size jointly shape establishment dynamics in discrete landscapes

Identifying the main factors driving introduced populations to establishment is a major challenge of invasion biology. Due to their small initial size, introduced populations are most vulnerable to extinction because of demographic stochasticity or Allee effects. While an increase in initial population size is known to increase establishment success, much remains to be understood regarding its interplay with connectivity in spatially structured environments. In order to better understand how demographic mechanisms interact at such spatial scale, we developed a stochastic model of population dynamics in discrete space to investigate the effect of connectivity and initial population size on establishment. The predictions derived from the model were then tested using experimental introductions of an insect parasitoid (Trichogramma chilonis) in spatially structured laboratory microcosms. Both theoretical and experimental results demonstrated that the connectivity of the introduction site had 1) a deleterious effect in the first generation when the introduced population was small and 2) a beneficial impact brought about by metapopulation effects in the subsequent generations. Interestingly, populations displayed a weakly pushed invasion pattern promoting early establishment, which was mainly underpinned by dispersal stochasticity and the discrete nature of the landscape. These results shed light on the critical influence of landscape connectivity on establishment dynamics.

Biological models

• invasive insects: the melybug Pseudococcus, the Asian ladybeetle Harmonia axyridis, Drosophila suzukii, and many others.

• insects introduced for biological control purposes: Trichogramma species.

Scientific originality of the team

We study invasion biology with various perspectives: behavioural ecology, population dynamics and population genetics. Another original characteristic of the team is its experimental approach to study invasive processes. We use biological control operations as an experimental model and we hope to use our results on invasion biology to improve biological control operations

Current Subject

Which demographic, genetic and environmental factors determine the success or failure of accidental invasions (introduction of a pest) or planned introductions (introduction and acclimatisation of a biological control agent)?

Scientific partnerships and support for programmes

• National collaborations: CBGP Montpellier, Bio3P Rennes, INA-PG, University Lyon 1, Plant Breeding and Genetics Division (GAFL) Avignon, CIRAD Montpellier, etc ;
• International collaborations: CSIRO Australia, EBCL/USDA Montpellier, University of Iowa, Colorado State University, University of Palermo, etc.

The research theme of the team receives support from various federative programmes and through calls for tender (Plant Health and Environment Division of INRA, PACA Regional Authority, Biodiversity Research Fundation (FRB)  and Research National Agency (ANR)).