Data from: Survival after pathogen exposure in group-living insects: don’t forget the stress of social isolation!

A major cost of group-living is its inherent risk of pathogen infection.
To limit this risk, many group-living animals have developed the
capability to prophylactically boost their immune system in the presence
of group members and/or to mount collective defenses against pathogens.
These two phenomena, called density dependent prophylaxis and social
immunity, respectively, are often used to explain why, in group-living
species, individuals survive better in groups than in isolation. However,
this survival difference may also reflect an alternative and often
overlooked process: a cost of social isolation on individuals’ capability
to fight against infections. Here, we disentangled the effects of
density-dependent prophylaxis, social immunity and stress of social
isolation on the survival after pathogen exposure in group-living adults
of the European earwig Forficula auricularia. By manipulating the presence
of group members both before and after pathogen exposure, we demonstrated
that the cost of being isolated after infection, but not the benefits of
social immunity or density-dependent prophylaxis, explained the survival
of females. Specifically, females kept constantly in groups or constantly
isolated had higher survival rates than females that were first in groups
and then isolated after infection. Our results also showed that this cost
of social isolation was absent in males, and that social isolation did not
reduce the survival of non-infected individuals. Overall, this study gives
a new perspective on the role of pathogens in social evolution, as it
suggests that an apparently non-adaptive, personal immune process may
promote the maintenance of group-living under pathogenic environments.