My research is mainly focused on population evolution of insect species of agricultural interest. I use molecular and evolutionary ecology to infer population histories and processes (e.g. routes of colonization, demographic quantities) and test for the roles of (a)biotic factors (e.g. landscape, microbial communities). My work also involves the identification of the target species under study and the evolutionary history of their lineages.
In Cirad, we have a long history with locust species, such as the Desert locust, Schistocerca gregaria (picture: Antoine Foucart, Augrabies Falls, South-Africa). These crop pests are subject to huge and unpredictable increases in population density, associated with a switch from the shy and cryptic to the highly active and aggregative behavior (phase polyphenism). We are interested in the environmental conditions leading to the evolution of population outbreaks and extreme density-dependent phenotypic plasticity in these species.
Characterization of the diversity of Orthopteran species associated with field crops and of their microbial communities
This initiative aims to contribute to the international efforts to develop species identification tools publicly accessible through the Internet for other orders of insects than Orthoptera. Such efforts are often applied at a deep taxonomic level by using high-throughput sequencing of multiple amplicons (e.g. mitochondrial barcode, nuclear fragments). At this level, we focus on ancient DNA from Western-African specimens of the diverse Acrididae family from our collection. Identification can otherwise be problematic at a recent taxonomic level, which requires integrative revisions based on morphological and molecular data. At this level, we focus on two case studies: we use the RAD-Seq technique and geometrical morphometry to explore species limits within the Calliptamus genus, and we combine microsatellite genotyping, mitochondrial barcoding, and morphological and ecological data to resolve the enigmatic genetic isolation of the ‘Palavas grasshopper', a giant form of the migratory locust. Finally, modern biocontrol of pests requires the ability to recognize not only target insect species but also their putative biocontrol agents, and we develop a tool for the identification of microorganisms, still in migratory locusts. Main collaborators: A. Foucart, J. Haran, M. Galan.
Evolutionary history and population dynamics of the desert locust
The desert locust is a polytypic species which is distributed in two distinct regions along the North-South axis of Africa. The nominal subspecies, S. g. gregaria, is one of the most widespread and harmful locust species with a huge potential invasion area in northern Africa. S. g. flaviventris is restricted to the south-western arid zone of Africa and swarms only rarely. My aims are to identify morphological and molecular diagnostic characters for desert locust subspecies, estimate key parameters of their independent evolutionary history (e.g. divergence time), better understand and compare their population structure and dynamics, inform on the divergence in propensity to gregarize, and characterize climatic causes behind each subspecies range limits. The natural variation in environments, genomes and phenotypes of the desert locust will serve to examine phase polyphenism with an integration of the functions of evolution (neutral drift and adaptive divergence), ecology (how fitness effects of phase translate in ecological performance of populations) and genetics (genes involved in phenotypic plasticity). Main collaborators: C.S. Bazelet, A. Estoup, A. Foucart, M. Lecoq, C. Meynard.
Quantitative genetics of phase polyphenism
The aim is to inform on reaction norms of polyphenic traits (e.g.
larval
behavior, larval growth, adult morphology) in a complex environment,
and on the associated genetic parameters (heritability of traits,
genetic correlations between growth environments and between components
of phase). We hope to disentangle the effect of growth conditions from
the effect of phase on the plastic response of locusts. We also explore
the genetic mechanisms involved in phenotypic plasticity. In a long
term, this biological
knowledge will serve for building an individual-based model to simulate
the demo-genetics dynamics of locust populations. Main collaborators: H.
Jourdan, B. Pélissié, C. Piou.
2007 - 2009, Marie-Curie Outgoing International Fellow, CBGP, Montpellier and University of Sydney, Australia, with G.A. Sword and S. J. Simpson
PhD. University of Montpellier, France 2006 (Supervisors: A. Estoup, Y. Michalakis & M. Lecoq)
MSc. University of Montpellier, France 2002 (Supervisor: A. Estoup)
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