Data from: Functional role of phenylacetic acid from metapleural gland secretions in controlling fungal pathogens in evolutionarily derived leafcutter ants

Fungus-farming ant colonies vary four to five orders of magnitude in size.
They employ compounds from actinomycete bacteria and exocrine glands as
antimicrobial agents. Atta colonies have millions of ants and are
particularly relevant for understanding hygienic strategies as they have
abandoned their ancestors' prime dependence on antibiotic-based
biological control in favour of using metapleural gland (MG) chemical
secretions. Atta MGs are unique in synthesizing large quantities of
phenylacetic acid (PAA), a known but little investigated antimicrobial
agent. We show that particularly the smallest workers greatly reduce
germination rates of Escovopsis and Metarhizium spores after actively
applying PAA to experimental infection targets in garden fragments and
transferring the spores to the ants' infrabuccal cavities. In vitro
assays further indicated that Escovopsis strains isolated from
evolutionarily derived leaf-cutting ants are less sensitive to PAA than
strains from phylogenetically more basal fungus-farming ants, consistent
with the dynamics of an evolutionary arms race between virulence and
control for Escovopsis, but not Metarhizium. Atta ants form larger
colonies with more extreme caste differentiation relative to other
attines, in societies characterized by an almost complete absence of
reproductive conflicts. We hypothesize that these changes are associated
with unique evolutionary innovations in chemical pest management that
appear robust against selection pressure for resistance by specialized
mycopathogens.