Recruitment of minor workers for defense against a specialized parasite of Atta leaf-cutting ant fungus gardens

TY - JOUR

T1 - Recruitment of minor workers for defense against a specialized parasite of Atta leaf-cutting ant fungus gardens

AU - Gerstner, A.T.

AU - Thomas-Poulsen, Michael

AU - Currie, C.R.

PY - 2011/1

Y1 - 2011/1

N2 - Social insects that obligately depend on mutualists are known to defend both themselves and their partners from exploitation. One example is leaf-cutting ants, which defend the mutualistic fungus they cultivate for food from potentially virulent specialized microfungal parasites (genus Escovopsis). Mechanisms employed by the ants to reduce the impact of Escovopsis include grooming the mycelium of their fungal cultivar and weeding out infected parts of the fungus garden. These behavioral defense tasks are performed by specific size castes: minor and major workers, respectively. While minor workers are efficient at removing Escovopsis spores through fungus grooming, they are significantly less mobile than major workers. This implies that if major workers were to facilitate the movement of minor workers from uninfected to infected sites within colonies, defense against Escovopsis potentially would be faster, and consequently more efficient. Using dual-chamber sub-colony set-up experiments, we explore the role major workers play in the movement of minors from uninfected to infected chambers in two leaf-cutting ant species, Atta cephalotes and A. sexdens. We find that the presence of major workers results in an increase in the movement of minors when gardens are infected with Escovopsis. This suggests that minor workers may be recruited to help defend the fungus garden from infection, providing an example of how colony social structure influences defense against pathogens in a social insect.

AB - Social insects that obligately depend on mutualists are known to defend both themselves and their partners from exploitation. One example is leaf-cutting ants, which defend the mutualistic fungus they cultivate for food from potentially virulent specialized microfungal parasites (genus Escovopsis). Mechanisms employed by the ants to reduce the impact of Escovopsis include grooming the mycelium of their fungal cultivar and weeding out infected parts of the fungus garden. These behavioral defense tasks are performed by specific size castes: minor and major workers, respectively. While minor workers are efficient at removing Escovopsis spores through fungus grooming, they are significantly less mobile than major workers. This implies that if major workers were to facilitate the movement of minor workers from uninfected to infected sites within colonies, defense against Escovopsis potentially would be faster, and consequently more efficient. Using dual-chamber sub-colony set-up experiments, we explore the role major workers play in the movement of minors from uninfected to infected chambers in two leaf-cutting ant species, Atta cephalotes and A. sexdens. We find that the presence of major workers results in an increase in the movement of minors when gardens are infected with Escovopsis. This suggests that minor workers may be recruited to help defend the fungus garden from infection, providing an example of how colony social structure influences defense against pathogens in a social insect.

U2 - 10.1080/03949370.2010.529828

DO - 10.1080/03949370.2010.529828

M3 - Journal article

SN - 0394-9370

VL - 23

SP - 61

EP - 75

JO - Ethology Ecology & Evolution

JF - Ethology Ecology & Evolution

IS - 1

ER -