Data from: Social immunity in a supercolonial invasive ant: Nest structure confers immune function

In animals, group living comes at the cost of increased pathogen exposure.
In kin groups, social immune behaviors offset that cost and reach their
most complex expression in eusocial insect societies. In the nests of
these societies, collective social behaviors can modify patterns of
individual interactions across space, reducing the ability of pathogens to
reach the reproductive core of the colony (organizational immunity). To be
effective, these behaviors must separate infected and uninfected
individuals, implying that the efficacy of social immune behaviors may
depend upon nest structure. The role of nest space has received little
attention, and most knowledge of social immune behavior in social insects
is based on the study of generalist entomopathogenic fungi. We examine the
social immune behaviors involved in the interaction between the
supercolonial, invasive tawny crazy ant (Nylanderia fulva), and its
specialist, intracellular, microsporidian pathogen Myrmecomorba
nylanderiae, to ask how nest structure influences social immunity. By
manipulating nest structure, we demonstrate that preventing pathogen
transmission to the colony core requires a multi-chambered nest. Without
which, social immune function was lost, and disease transmission was
universal. To understand how nest space enhances social immune efficacy,
we first confirm that workers within tawny crazy ant nests form spatially
and behaviorally segregated social sub-networks. We then find that
infected ants introduced into the colony core migrate to the colony
periphery, while uninfected ants do not. Behavioral tests indicate that,
despite the infection being internal, uninfected ants can detect the
infection status of a worker; thus, behaviors enforcing spatial
segregation could be triggered by either party. Additionally, infected
ants alter the behavioral tasks they perform, assuming more corpse removal
tasks, particularly infected corpse removal, and reducing their efforts in
foraging and brood care. With some exceptions, the social immune behaviors
expressed by this supercolonial ant in response to microsporidian
infection correspond to immune defense behaviors employed to defend
against generalist entomopathogenic fungi. These behaviors appear to be
conserved, generalized responses to pathogen infection among social
insects.