Data from: Pheromone-induced accuracy of nestmate recognition in carpenter ants: simultaneous decrease of Type I and Type II errors

The ecological and evolutionary success of social insects relies on their
ability to efficiently discriminate between group members and aliens.
Nestmate recognition occurs by phenotype matching, the comparison of the
referent (colony) phenotype to the one of an encountered individual. Based
on the level of dissimilarity between the two, the discriminator accepts
or rejects the target. The tolerated degree of mismatch is predicted by
the acceptance threshold model, which assumes adaptive threshold shifts
depending on the costs of discrimination errors. Inherent in the model is
that rejection (Type I) and acceptance (Type II) errors are reciprocally
related: if one type decreases, the other increases. We studied whether
alarm pheromones modulate the acceptance threshold. We exposed Camponotus
aethiops ants to formic acid and subsequently measured aggression towards
nestmates and non-nestmates. Formic acid induced both more non-nestmate
rejection and more nestmate acceptance than a control treatment, thus
uncovering an unexpected effect of an alarm pheromone on responses to
nestmates. Nestmate discrimination accuracy was improved via a decrease of
both types of errors, a result that cannot be explained by a shift in the
acceptance threshold. We propose that formic acid increases the amount of
information available to the ants, thus decreasing the perceived
phenotypic overlap between nestmate and non-nestmate recognition cues.
This mechanism for improved discrimination reveals a novel function of
alarm pheromones in recognition processes and may have far-reaching
implications in our understanding of the modus operandi of recognition
systems in general.