“Social immunity and sanitary strategies in ant societies”

Social insects have succeeded in limiting interactions with life-threatening organisms such as pathogens that are originating from waste, corpses or surrounding environment. Ant societies have thus evolved physical (cuticular barrier), immune response or behavioral defenses that make nestmates less vulnerable to diseases. In addition to these individual defenses, social mechanisms of prophylaxy and hygiene are collectively achieved within ant societies. This so-called social immunity is the central theme of a growing stream of our research in which we compare collective sanitary strategies which have evolved according to the pathogenic risks or to the ant species’ life traits.

“Ant-aphid mutualism”

In return for honeydew supply, ants defend sap feeders against natural ennemies and parasitoids, but also provide them with hygiene and cleaning. Evolution has tailored honeydew composition and production to suit the needs of their ant mutualists and to promote persistent  interactions between partners. We aim at identifying which life traits of myrmecophilous aphids are relevant to ants for cementing their attendance and whether semiochemicals originating from aphids, host plant or honeydew microfauna, allow ants to detect and discriminate between aphid partners. Recently, we investigate how increased temperature and/or higher carbon dioxyde levels expected from climate changes may shape this famous ant-aphid mutualism.

“Ant-plant relationships”

Seed dispersal by ants – also called myrmecohcory – involves many different species and shows a wide geographical and temporal variability that makes it a complex phenomenon. We develop an integrative approach of myrmecohcory by taking into account the plant phenology, the foraging behavior of dispersing ants as well as the environmental constraints exerted on both partners. Since plants are competing for the ants’ services, we investigate how several seed traits or the chemical attractiveness of elaiosomes arouse the interest of ant workers. The key-factors that determine the payoff and “loyalty” of each partner are identified to understand the transient or permanent status of this sticking ant-plant relationship.

“Individual decision-making and collective behavior in ant societies”

All biological systems have complex organization at different levels. On can readily sense the complexity of biological interactions by looking at the coordinated movements of schooling fishes or of flying birds. Likewise, ant societies are well-known for the diversity and complexity of their collective behavior. Adaptive patterns such as the collective selection of the best food resource or the building of an efficient trail network emerge from the multiple interactions between hundredths of individuals. We are interested in understanding the basic behavioural rules that are followed by individuals as well as their response to environmental cues. For instance, in the context of foraging, the following questions arise: How do ants assess food characteristics? What is the functional value of the decision criteria used by ants ? What level of complexity is required at the individual level to lead to the emergence of complex responses at the collective level ?

“Polymorphism and division of labour in ant societies”

A major trait of sociality is the integration and coordination of groups of behaviourally specialized workers (coupled or not with caste polymorphism). We try to evaluate the impact of such specialization on the efficiency of collective strategies in foraging, nest defence or brood care. Division of labour is related to caste physiology and caste implication in information transfer within the ant society.

“Self-organisation in biological systems”

In the living word, numerous collective structures- sometimes complex ones- outcome from a limited number of physico-chemical laws and simple behavioural rules that are coupled with amplifying phenomena. We assess the generic value of such rules for many different animal species (insects, fishes, primates,…) in which we census multiple forms of self-organization.

“Bioinspiration : towards mixed societies of natural and artificial agents”

Behaviour as in animal populations can be implemented not only in computer simulations but also in simple robots. Our group is demonstrating experimentally that mixed societies of insects and robots can co-operate and self-organize based on the behavioural algorithms used by insects. Moreover, through the use of artificial agents it should be possible to trigger and control arising patterns in animal groups.