Data from: Alate susceptibility in ants

Pathogens are predicted to pose a particular threat to eusocial insects
because infections can spread rapidly in colonies with high densities of
closely related individuals. In ants, there are two major castes: workers
and reproductives. Sterile workers receive no direct benefit from
investing in immunity, but can gain indirect fitness benefits if their
immunity aids the survival of their fertile siblings. Virgin reproductives
(alates), on the other hand, may be able to increase their investment in
reproduction, rather than in immunity, because of the protection they
receive from workers. Thus, we expect colonies to have highly immune
workers, but relatively more susceptible alates. We examined the survival
of workers, gynes, and males of nine ant species collected in Peru and
Canada when exposed to the entomopathogenic fungus Beauveria bassiana. For
the seven species in which treatment with B. bassiana increased ant
mortality relative to controls, we found workers were significantly less
susceptible compared with both alate sexes. Female and male alates did not
differ significantly in their immunocompetence. Our results suggest that,
as with other nonreproductive tasks in ant colonies like foraging and nest
maintenance, workers have primary responsibility for colony immunity,
allowing alates to specialize on reproduction. We highlight the importance
of colony-level selection on individual immunity in ants and other
eusocial organisms.