My research deals with the evolution of behavior in insects. I reconstruct phylogenies before using them as a historical reference to test evolutionary hypotheses. Following this phylogenetic approach, I mainly investigate the evolution of social behavior in termites and cockroaches (Insecta : Dictyoptera).
Nasutitermitinae, soldiers and workers in Singapore © MNHN
Given its paradoxical dimension with regard to natural selection, social behavior has long been of central interest in biology. Indeed, in the “Origin of species”, Darwin already mentioned how sterile castes of insect societies were a “special difficulty, which at first appeared to [him] insuperable”.
Living in a group brings diverse advantages and constraints to individuals. If advantages exceed drawbacks, natural selection can readily explain group living origin. Few exaggerated forms of social behavior like altruism, however, seem hardly interpretable in the only light of natural selection. Thus, social behavior evolution still remains a tremendous challenge, which is taken up using different approaches : ethology, population genetics, phylogeny, genomics…
My work aims at studying the evolution of social behavior in a phylogenetic framework.
1. Social evolution and evolutionary trends
Social behavior evolution has always been seen as a progressive, irreversible and complexity-increasing path, with eusociality as the ultimate step. Even though some exceptions to this linear trend have been shown, ‘laws’ of specialization and of irreversibility are still closely tied to the evolution of social behavior.
Social categories, from Wilson (1971) © MNHN
Classification of social categories illustrates these evolutionary trends, each category being a more complex step than the previous one. Complexity increase with the acquisition of one or several key features, which would make individuals better adapted to their environment and thus would be selectively advantageous.
These evolutionary trends can be tested in a phylogenetic framework : Comparing expected patterns under a null hypothesis (e.g., evolution is linear) with the observed patterns enable us to evaluate how adequate to social evolution of our model organisms this hypothesis is.
2. Evolutionary forces and modalities of social evolution
In social behavior classification, a switch from one category to another is associated with the acquisition of at least one key feature. The acquisition of such key features has been explained mostly in a functional context. In other words, key features are seen as adaptations.
The aptive triangle, from Gould (2002) © MNHN
This scenario overemphasizes the importance of ecological pressures in social behavior evolution to the detriment of other pressures. Yet, alternatives and complements to natural selection (e.g., phylogenetic inertia) may play a significant role in social evolution.
Phylogenetic analyses and behavioral observations can help to highlight the relative importance of these different forces.
3. Phylogenetic analysis of behavior
Studying the evolution of behavior in a phylogenetic framework requires the availability of phylogenetic hypotheses. Consequently, the first step of most of my research projects is to build a phylogenetic hypothesis using molecules and/or morphology. Non-traditional characters like behavioral ones are also integrated in phylogenetic matrices. Such process allows a better definition of behaviors observed and also a more thorough investigation of social behavior evolution hypotheses. But it might also require adapting or developing methodology to reach an adequate phylogenetic framework.
Therefore, building new tools for the phylogenetic analysis of behavior is part of my research projects.
- Action Transversale du MNHN (20,000 €) - 2011-2015.
- Lavoisier Grant (18,000 €), Ministère des Affaires Etrangères, December 2007 - December 2008.
- Rosen Price (500 $), 3rd best student oral presentation, Hennig XXV, Oaxaca (Mexico), 2006.
- Marie Stopes Student Travel Award (500 $) in 2005, 2006 and 2007.
- Travel Grant from Paris Doctoral School ED 392 (1,000 €) in 2006 and 2007
- PhD Grant, Ministère de l’Education nationale, de la Recherche et des Technologies, October 2004 - September 2007.
- Master 2 Grant, Ministère de l’Education nationale, de la Recherche et des Technologies, October 2003 - June 2004.