Colony introduction assays to study nestmate discrimination of the ant Pristomyrmex punctatus

Social animals utilise various communication methods to organise their
societies. In social insects, nestmate discrimination plays a crucial role
in regulating colony membership. Counter to this system, socially
parasitic species employ diverse behavioural and chemical strategies to
bypass their host’s detection. In this study, we tested whether such
parasitic adaptations could be detected in the incipient stage of social
parasitism that is observed as intraspecific phenomena in some social
insects. The Japanese parthenogenetic ant Pristomyrmex punctatus harbours
a genetically distinct cheater lineage which infiltrates and exploits host
colonies. We found that intrusion of this intraspecific social parasite
was defended by nestmate discrimination of host colonies without any
behavioural strategies specialised in social parasitism. Most of the
cheaters were eliminated through aggression by host workers that are
typically observed against non-nestmates, resulting in a low intrusion
success rate for the cheaters (6.7%). Our result contrasts with the
expectation from interspecific social parasitism but rather resembles the
intraspecific counterpart reported in Cape honeybees (Apis mellifera
capensis), illustrating the role of nestmate discrimination in defence
against the intrusion of intraspecific social parasites.