Last update: : Tuesday 23 February 2016, by
Par : Dr. Nathalie Stroeymeyt, University of Lausanne
Date : vendredi 29 avril 2016 à 13h
Lieu : IPHC, Amphithéâtre Grünewald, bâtiment 25
Social insects live in dense, highly interactive groups of closely related individuals. They are therefore highly vulnerable to disease and have evolved collective defences to prevent entry and spread of pathogens into colonies. Selection for disease control is believed to have influenced the social organisation of insect colonies, for example by favouring their spatial and social compartmentalisation, thus impeding pathogen spread and protecting the queen and young workers from outside pathogens (‘organisational immunity’). Here we tested quantitatively whether the structure of interaction networks does confer disease protection in colonies of the ant Lasius niger. We automatically tracked the movement and interactions of all colony members before and after exposing a subset of workers to the entomopathogenic fungus Metarhizium brunneum, and we determined the fungal load of all individuals one day after exposure. We then combined network analysis with epidemiological modelling to uncover the transmission dynamics of the pathogen and determine the infection risk of individuals depending on their age, social task, and position in the network. Our results provide evidence for organisational immunity, suggesting that both inherent colony organisation and changes in the interaction patterns of the ants upon pathogen exposure slow down disease spread within the colony.