Dr. Romain Libbrecht
|Since 2016||Assistant professor / Group leader, University of Mainz, Germany|
|2016||Postdoctoral researcher, University of Lausanne (Keller lab), Switzerland|
|2015-2016||Marie Curie postdoctoral fellow - return phase, University of Lausanne (Keller lab), Switzerland|
|2013-2015||Marie Curie postdoctoral fellow - outgoing phase, The Rockefeller University (Kronauer lab), New York, USA|
|2012||Postdoctoral researcher, University of Lausanne (Keller lab), Switzerland|
|2007-2012||PhD thesis (Division of labor in insect societies: genetic components and physiological regulation - Supervisor: Prof L. Keller), University of Lausanne, Switzerland|
|2007||MSc (Thermal acclimation in the tropical beetle Alphitobius diaperinus - Supervisor: Dr D. Renault), University of Rennes, France|
|2005-2006||Internship (Foraging strategy in the parasitoid wasp Aphidius ervi - Supervisor: Dr M. Fellowes), University of Reading, UK|
|2003-2007||Engineering studies in biology and agronomy, Ecole Nationale Supérieure d’Agronomie de Rennes, France|
|2001-2003||Preparatory class in biology, Lille, France|
I have a broad interest in understanding the organization and evolution of social life in insect societies. In this perspective, my group uses different approaches to study the genetic, genomic, epigenetic, behavioral and physiological mechanisms involved in the alternative production of queens and workers, the division of labor among workers, and more generally the regulation of reproduction, nutrition and behavior in several species of ants. More information about the current research conducted in my group is available on the group page. Below are summaries of some of the research projects I have conducted in the past. If you have any questions about my past and current research, and/or if you are interested in doing a bachelor, master, PhD or postdoc project in my group, do not hesitate to contact me.
The role of DNA methylation in social insects
DNA methylation is a relatively new field in social insects, and there is a need for more controlled, carefully replicated investigations to determine whether different castes (e.g., queen vs worker) are associated with different patterns of DNA methylation. As a Marie Curie postdoctoral fellow in the Kronauer lab at The Rockefeller University and in the Keller lab at the University of Lausanne, I have investigated whether epigenetic modifications regulate reproduction and behavior in the parthenogenetic ant Cerapachys biroi. I have used whole-genome bisulfite sequencing and RNA sequencing to compare DNA methylation, gene expression and alternative splicing patterns between brains of individuals that differ in reproduction and behavior, while controlling for their age and genetic background. Not only did I find that brain DNA methylation in the clonal raider ant is robust and not associated with different reproductive and behavioral states, but also showed that the current evidence for caste-specific DNA methylation in social insects is actually very weak, thus providing valuable information on the role and mode of action of DNA methylation in insect societies.
Libbrecht R., Oxley P., Keller L., Kronauer, D. (2016) Robust DNA methylation in the clonal raider ant brain. Current Biology 26(3):R391-395
The mechanisms behind maternal effects on polyphenism
Polyphenism is the phenomenon where alternative phenotypes are produced by a single genotype in response to environmental cues. An extreme case is found in social insects, where reproductive queens and sterile workers that greatly differ in morphology and behavior can arise from a single genotype. The first experimental evidence for maternal effects on caste determination, the differential larval development toward the queen or worker caste, was documented in Pogonomyrmex seed-harvester ants, in which only colonies with a hibernated queen produce new queens. However, the proximate mechanisms behind those intergenerational effects have remained elusive. During my PhD with Prof. Laurent Keller at the University of Lausanne, I used a combination of artificial hibernation, hormonal treatments, gene expression analyses and vitellogenin quantification to investigate how the combined effect of environmental cues and hormonal signaling affects the process of caste determination in Pogonomyrmex ants. The results show that the interplay between insulin signaling, juvenile hormone and vitellogenin regulates maternal effects on the production of alternative phenotypes and identify vitellogenin as a potential major player in the intergenerational transmission of information. This reveals how environmental cues experienced by one generation can translate into phenotypic variation in the next generation.
Libbrecht R., Corona M., Wende F., Dihego D., Serrao J. and Keller L. (2013) Interplay between insulin signaling, juvenile hormone and vitellogenin regulates maternal effects on caste allocation in ants. PNAS 110: 11050-11055
The reproductive ground plan hypothesis
The reproductive ground plan hypothesis (RGPH), originally developed in honeybees, posits that mechanisms regulating reproduction in solitary species have been co-opted to regulate the behavior of sterile workers in social species. To test whether such mechanisms could regulate division of labor in ants, Dr. Miguel Corona and I used the harvester ant Pogonomyrmex barbatus to compare the expression of two genes (Vg1 and Vg2) involved in the production of vitellogenin (usually involved in reproduction). The finding of differential gene expression between individuals that differ in reproduction (queens and workers) and in behavior (nurses and foragers) supports the RGPH in ants. This confirms that the RGPH is likely to be important for the evolution of sociality, as both ants and bees co- opted mechanisms involved in the regulation of reproduction to regulate division of labor among sterile individuals, even though they evolved sociality independently.
*Corona M., *Libbrecht R., Wurm Y., Riba-Grognuz O., Studer R.S. and Keller L. (2013) Vitellogenin underwent subfunctionalization to acquire caste and behavioral specific expression in the harvester ant Pogonomyrmex barbatus. PloS Genetics 9(8): e1003730 *These authors contributed equally to the work
Genetic compatibility affects worker behavior in ants
Division of labor among workers is central to the organization of insect societies. Within-colony comparisons between subfamilies of workers (patrilines or matrilines) revealed genetic effects on worker behavior in many social insect species. Although this has been taken as evidence for additive genetic effects stemming from simple allelic differences, this conclusion has never been experimentally tested. During my PhD with Prof. Laurent Keller at the University of Lausanne, I used the Argentine ant Linepithema humile to tackle this issue. This species can mate in the laboratory, thus offering a unique opportunity to perform controlled crosses. Combined with different phenotypic measurements and behavioral analyses, such controlled crosses revealed the existence of complex, non-additive genetic influences (e.g., genetic compatibility, epistasis and parent-of-origin specific imprinting effects) on worker behavior. This is in strong contrast with the current view and has important consequences for our understanding of division of labor in insect societies.
Libbrecht R. & Keller L. (2012) Genetic compatibility affects division of labor in the Argentine ant Linepithema humile. Evolution 67: 517-524
The genetic components to caste allocation in ants
Social insect colonies are characterized by a reproductive division of labor and the coexistence of distinct castes. In social insect species with multiple queens per colony, the fitness of nestmate queens directly depends on the process of caste allocation (i.e., the relative investment in queen, sterile worker and male production). During my PhD with Prof. Laurent Keller at the University of Lausanne, I have investigated the genetic components to the process of caste allocation in a multiple-queen ant species. I conducted controlled crosses in the Argentine ant Linepithema humile to identify maternal and paternal family effects on the relative production of new queens, workers and males. In addition to revealing complex non-additive genetic effects on female caste determination in a multiple-queen ant species, this study revealed strong genetic compatibility effects between parental genomes on caste allocation. These results are important because they suggest an epigenetic regulation of caste determination in L. humile and provide a better understanding for the maintenance of queen specialization in multiple-queen ant species.
Libbrecht R., Schwander T., Keller L. (2011) Genetic components to caste allocation in a multiple-queen ant species. Evolution 65: 2907-2915.
Kohlmeier P, Alleman A, Libbrecht R, Foitzik S*, Feldmeyer B*. Gene expression is more strongly associated with behavioural specialisation than with age or fertility in ant workers. Molecular Ecology, in press (*shared last author)
Libbrecht R, Oxley PR & Kronauer DJC. 2018. Clonal raider ant brain transcriptomics identifies candidate molecular mechanisms for reproductive division of labor. BMC Biology, 16:89.
Chandra V, Fetter-Pruneda I, Oxley PR, Ritger A, McKenzie S, Libbrecht R & Kronauer DJC. 2018. Social regulation of insulin signaling and the evolution of eusociality in ants. Science, 361: 398-402
Weitekamp CA, Libbrecht R and Keller L. (2017) Genetics and evolution of social behavior in insects. Annual Review of Genetics, 51: 219-239.
Libbrecht R, Oxley PR, Keller L & Kronauer DJC (2016) Robust DNA methylation in the clonal raider ant brain. Current Biology 26(3): R391-R395
Corona M, Libbrecht R & Wheeler D (2016) Molecular mechanisms of phenotypic plasticity in social insects. Current opinion in insect science 13: 55-60
Ulrich Y, Burns D, Libbrecht R & Kronauer DJC (2015) Ant larvae regulate worker foraging behavior and ovarian activity in a dose-dependent manner. Behavioral Ecology and Sociobiology - Online first
Libbrecht R & Keller L (2015) The making of eusociality: insights from two bumblebee genomes. Genome Biology 16: 75 - Dispatch
Libbrecht R & Kronauer D (2014) Convergent evolution: the genetics of queen number in ants. Current Biology 24(22): R1083-R1085 - Dispatch
Schwander T, Libbrecht R, Keller L (2014) Supergenes and complex phenotypes. Current Biology 24(7): R288-R294
Corona* M, Libbrecht* R, Wurm Y, Riba-Grognuz O, Studer RS & Keller L (2013) Vitellogenin underwent subfunctionalization to acquire caste and behavioral specific expression in the harvester ant Pogonomyrmex barbatus. Plos Genetics 9(8): e1003730 - *co-first authors
Libbrecht R, Oxley PR, Kronauer DJC, Keller L (2013) Ant genomics sheds light on the molecular regulation of social organization. Genome Biology 14: 212-219
Libbrecht R, Corona M, Wende F, Azevedo D, Serrao J, and Keller L (2013) Interplay between insulin signaling, juvenile hormone and vitellogenin regulates maternal effects on caste polyphenism in ants. PNAS 110(27): 11050-11055
Libbrecht R & Keller L (2012) Genetic compatibility affects division of labor in the Argentine ant Linepithema humile. Evolution 67(2): 517-524
Libbrecht R, Schwander T, Keller L (2011) Genetic components to caste allocation in a multiple-queen ant species. Evolution 65(10): 2907-2915
Libbrecht R, Gwynn DM, Fellowes MDE (2007) Aphidius ervi preferentially attacks the green morph of the pea aphid, Acyrthosiphon pisum. Journal of Insect Behavior 20(1): 25-32