Disease recognition and collective defence in insect societies
Final Report Abstract
Disease dynamics in societies are affected by the genetic variation between group members. We tested the effect of reduced genetic diversity in ant colonies on the ants’ susceptibility to disease. We found that colonies with higher genetic diversity performed more social immune defences, i.e. collective measures against disease such as allogrooming of an exposed nestmate than colonies with restricted genetic diversity – be it due to clonal reproduction or sib‐mating and thus inbreeding. Interestingly, we found that inbreeding does not per se reduce the immunocompetence of individual group members or their repertoire of hygienic behaviours expressed against pathogens in the colony. Instead, we could show for the first time that inbreeding in ants affects the efficiency of their social immune defences as it delays switching on their defences, probably due to a reduced ability to detect the pathogen. Whereas genetically diverse ants possess the capacity to immediately detect incoming pathogens in their colony, inbred ants did neither intensively groom brood treated with spores of a fungal pathogen, nor removed this brood early from the nest. However, they removed the brood three to four days later when the pathogen had established an infection. High genetic diversity is thus advantageous in anti‐pathogen defences in ants. Moreover, ant colonies are more efficient to cope with a disease at its early stages, i.e. if most group members are not stressed and still healthy. Only then can they perform efficient individual and social immune defences. A quick and efficient pathogen detection is thus crucial for ants to prevent epidemics in their societies.
Publications
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(2009) Analogies in the evolution of individual and social immunity. Philosophical Transactions of the Royal Society London B 364: 129‐142
Cremer, S. & Sixt, M.
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(2010) Rapid anti‐ pathogen response in ant societies relies on high genetic diversity. Proceedings of the Royal Society B: Biological Sciences, online early May 5 2010.
Ugelvig, L.V., Kronauer, D.J.C., Schrempf A., Heinze, J. & Cremer, S.
