Claire Mérot

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Research interest

Every day, whether I go walking in a garden or have a look at my plate, I am impressed by the incredible diversity of life on Earth. Biological diversity, recently named"Biodiversity", is a multiplicity of species but also shapes, colours, characters, and at a larger scale, a large variety of environments, with their own community of species.

My research interests are part of this general aim to understand the evolution of biodiversity on several timescales and at different levels. Actual diversity is the result of millions of years of evolution... And it can change and be altered very suddenly, for example due to human activities. I aim to better understand the evolutionary processes that shape the diversity of species, traits and genomes. Reciprocally, I also ask how does the genomic architecture or some adaptive traits contribute to the evolution of diversity.

Studying evolution requires the integration of several approaches and I like working with a combination of different methods: observations and experimentation in the field, molecular biology, genomics, lab analysis and modelling.

If you are interested in doing a post-doc, PhD or internship with me, please contact me at claire.merot[@]

ERC-funded project: EVOL SV 2024-2028

The role of structural genomic variants in eco-evolutionary processes

I am actively recruiting post-docs, PhD students, lab technicians, and students on this project. Please get in touch if you are interested!

Genetic diversity is a fundamental level of biodiversity at a time of global change. It provides variation that underpins species persistence and their adaptation to changing environments. Variation in the direction or presence of DNA sequences has been largely overlooked until now. Yet, those structural variants (SVs) represent a key aspect of genetic diversity. SVs cover 3 to 10 times more of the genome than the well-studied single-nucleotide variants and have different properties (length, effect on recombination, mutation rate). Structural variation thus represents a quantitative and qualitative shift in our understanding of genetic diversity, with predicted, but understudied, implications for evolution.

The project EVOL-SV calls for a reassessment of the genomic basis of eco-evolutionary processes. We propose new research avenues on the impact of SVs in ecology and evolution and to determine the contribution of SVs to current biodiversity. My team combine cutting-edge genomics and powerful experimental approaches, developed throughout my career, to perform multidisciplinary research on a focal system, Coelopa flies, and then across taxa.

We investigate SVs within a population genetic framework in Coelopa spp. to determine how SV properties affect their distribution and effects on fitness. We assess the contribution of SVs to deleterious load in a case of range shift northwards. We examine how SVs contribute to phenotypic adaptation, focusing on parallel climatic gradients and rapid thermal variation. Finally, at a broader phylogenetic level, we will draw general principles about the evolution of structural genetic diversity.

We hope that EVOL-SV will have long-term impacts by providing the first comprehensive assessment of structural genetic diversity across the tree of life, developing the study of SVs in non-model species, and determining how genetic architecture contributes to evolutionary response in a rapidly changing world.

Present projects (CNRS, Université Rennes)

The role of chromosomal inversion in adaptation to heterogenous environments in seaweed flies

Species evolution and adaptation has been suggested to be enhanced by certain genomic structures. One of these are inversions, where a segment of the chromosome breaks, is reversed and then re-inserted. The most compelling aspects of inversions is reduced recombination due to a decrease in synapsis formation in heterozygotes. As a result, inversions accumulate more variation than collinear regions and show intriguing patterns, such as varying in frequency along ecological clines, being involved in hybrid vigour, and harbouring an overabundance of loci involved in adaptation, population divergence and speciation.

An important axis of research thus addresses the role of inversions in adaptation by means of a multi-layer integrative approach using the seaweed fly Coelopa frigida as a model species. By combining the population ecology, genomics and laboratory experiments, we investigate the association between inversions and adaptation to heterogeneous environments. we am also explicitely testing fitness in the lab and investigating functionally the genetic basis of local adaptation. This project is undertaken by Léa Nicolas for her PhD.

Our aim is to shed light on the modalities by which very large chromosomal inversions contribute to adaptation in a non-model species and the selective forces and genetic mechanisms underlying the evolution of such structures.

Past post-doc project (University Laval, Québec)

A supergene inversion polymorphism in seaweed flies

My research focused on a big chromosomal inversion affecting multiple traits (sometimes called supergene) in the seaweed fly Coelopa frigida . By studying the population ecology, genomics and inversion frequencies in natural populations we investigated the implication of this inversion in local adaptation.

Then, using laboratory experiments, we explicitely tested fitness and modelled the different mechanisms of balancing selection that maintained the inversion polymorphism.

Past project (MNHN, Paris): Speciation in mimetic butterflies

PhD: Speciation in Heliconius butterflies: The balance between mimicry convergence and ecological divergence.

Recent radiations, such as the mimetic radiation of Heliconius butterflies in the Neotropics, offer an excellent example to address the evolutionary processes involved in speciation with gene flow. During my thesis, I explored an interesting situation in the Heliconius clade: two sibling species that are co-mimics of each other, sharing a similar wing colour pattern. This offers the possibility to study the limits of the classical model of speciation associated with shifts in wing pattern, usually described in this group. Colour pattern divergence indeed triggers strong reproductive isolation through disruptive natural selection for Müllerian mimicry and through sexual selection and assortative mating. I investigated how Müllerian mimicry affects species differentiation and reproductive isolation.

Specifically, I explored genetic divergence, coexistence, mimetic relationship and isolating barriers between the co-mimics H. timareta thelxinoe and H. melpomene amaryllis. I showed that the two species maintain consistent genetic and phenotypic divergence while hybridizing at low frequency. They display close resemblance in colour pattern, whose accuracy is affected by the composition of local mimetic community. Through controlled crosses, I showed that hybrids are intermediate in wing pattern and shape, suggesting that predation does not trigger strong post-mating isolation. However, behavioural sexual pre-mating isolation is high due to mate choice, likely relying on chemical cues.

Overall, my results confirmed that Müllerian mimicry between closely-related species likely enhances gene flow and acts against species differentiation. Nevertheless, this effect is balanced by the multidimensionality of isolating barriers, triggered by other ecological factors driving divergence.

For more details, I invit you to contact me or to consult my communications and publications