Grégory MOLLOT

Post Doctoral Fellow

CEFE/CNRS
Campus du CNRS
1919, route de Mende
34293 Montpellier 5

Tél : +33/0 4 67 61 .. ..
Fax : +33/0 4 67 61 33 36

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Research topics

My work is focused on food web studies. The theory of food web helps to explain energy and matter fluxes through trophic interactions (feeding relationship) that exist between species in an ecosystem. Food webs are unidirectional, i.e. the flow occurs only in one direction : species A feed on species B, in this simple scheme, A is the consumer and B is the resource. The assembly of interactions by considering overall species in the system is the food web. The study of ecological systems through the food web theory allows the use of statistical tools developed to complex network analyses, for instance, structural analysis of a food web can provide information on functioning and stability (resilience/persistence). This approach can be very interesting to study the effect of a disturbance, as a biological invasion or extinction of species, on the stability of the food web.

The main difficulty faced with this approach is to reach an accurate description of the food web structure. In fact, food webs typically consists of hundreds or even thousands of interactions between species, and such set of interactions is dynamically altered in time and space. The construction of a food web by traditional methods (observation, bibliographic data compilation, etc…) can be very time-consuming and unsuitable. During my PhD, I worked on a DNA metabarcoding approach to effectively characterize the diet of arthropods, and I was able to reconstruct the food web of a banana plantation in the Caribbean. The approach is divided into four tasks:

1. Construction of a reference library with DNA barcodes of all species present in the system
2. Sampling and dissection of the gut content of each sampled specimen, DNA extraction, PCR and high-throughput sequencing
3. Identification of sequences by bioinformatics analysis (alignment of each raw sequence from the sequencing with all sequences included in the reference library)
4. The result is a binary interaction matrix (presence / absence) or semi-quantitative (for a given consumer species: proportion of individuals in which we detected the DNA of a given resource) that represents the consumer / resource interactions.

In the case of the Caribbean banana plantation, the approach identified three species of predators consuming the main pest of bananas (the banana weevil). This also helped to highlight the effect of the addition of a cover crop in a banana plantation on the food web structure, compared to a banana plantation on a bare soil: significant diet change of generalists predators to feed on alternative prey supported by the cover crop (here, Diptera). The result challenged our expectations, the underlying hypothesis being that the cover crop provides alternative prey (such as Diptera), which will allow an increase of predators abundances and therefore increased predation rate on the pest through apparent competition mechanism. Although we have observed the presence of alternative prey and increased predators’ abundances, we did not observe an increase of predation rate on the pest. Probably the high abundance of alternative prey and the easy-access to this food skewed the apparent competition in favour of alternative prey.

I am currently working on a meta-analysis (CESAB-FRB funding), which aims to highlight the effect of biological invasions on the food web structure and stability. This work will contribute to the design of a prediction model of biological invasions. (Supervisors : Patrice David & François Massol)

Brief CV

2014-2017 : Postdoc CNRS-CEFE (Montpellier), meta-analysis of the effect of biological invasions on food web stability.

2013-2014 : Postdoc INRA-PSH (Avignon), arthropods movement tracking with ovalbumin (white eggs powder) and ELISA immunoassay in apple orchards

2009-2012 : PhD CIRAD-PRAM Banana, plantain and pineapple cropping systems (Martinique, FWI), DNA metabarcoding and structural analysis of a banana food web

Publications

Mollot G, Duyck PF, Borowiec N, Glennac S, Quilici S (2015) Life-history traits of Encarsia guadeloupae, a natural enemy of the invasive spiralling whitefly Aleurodicus dispersus. Journal of Applied Entomology (in revision)

Mollot G, Duyck PF, Lefeuvre P, Lescourret F, Martin JF, Piry S, Canard E, Tixier P (2014) Cover cropping alters the diet of arthropods in a banana plantation: a metabarcoding approach. PLoS One e93740

Tixier P, Dagneaux D, Mollot G, Vinatier F, Duyck PF (2013) Weeds mediate the level of intraguild predation in arthropod food webs. Journal of Applied Entomology 137 (9) : 702-710

Tixier P, Peyrard N, Aubertot JN, Gaba S, Radoszycki J, Caron-Lormier G, Vinatier F, Mollot G, Sabbadin R (2013) Modelling interaction networks for enhanced ecosystem services in agroecosystems. Advances in Ecological Research 49 : 437-480

Mollot G, Tixier P, Lescourret F, Quilici S, Duyck PF (2012) New primary resource increase predation on a pest in a banana agroecosystem. Agricultural & Forest Entomology 14 (3) : 317-323