Advanced social organization has evolved in the ants, bees, wasps and termites, which all live in colonies characterized by kinship-based reproductive division of labour. Leaf-cutting ants are particularly advanced because they rear fungi for food; this ob ligate 'agricultural' mutualism has allowed these ants to evolve colonies of 5 million workers. These ant societies have become so well organized that the major threats no longer come from predators or periods of food shortage, but from continuously present and rapidly evolving diseases. To survive the last ca. 50 million years leafcutters have evolved effective social defences against infections.
(1) unique actinomycete bacteria that the ants grow on their bodies to produce antibiotics targeted at a chronic disease of their gardens;
(2) glandular secretions with general antimicrobial properties; and
(3) sophisticated preventive allo- and self-grooming behaviours.
However, no studies have as yet addressed the interactions between social disea se defences and the much older individual immune defences that ants share with all non social insects. With a background in insect immunity, I will examine leaf-cutting ants to study how individual protection (immunity) can optimally complement protection from a social context. These questions are non-trivial, because the costs of all defences have to be paid from a common pool, so that investing more in one type will imply that others get less. Leaf-cutting ants have existed long enough for natural selection to offer them evolutionary stable solutions. Clarifying how these evolutionary dilemmas have been resolved is both of fundamental interest in evolutionary biology, and may provide interesting hints about immune investment and social disease management in our own societies. This proposal will allow bi-directional transfer of knowledge and skills between the host institute and myself and will make an essential contribution to my scientific career.
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