Two aggressive neighbours living peacefully: the nesting association between a stingless bee and the bullet ant

Abstract

Stingless bees often associate with termites, while association with ants is uncommon due to the high costs related to the aggressiveness of ants. Few combative genera of stingless bees can associate with a larger number of hosts, including ants. Here, we describe for the first time the association between a stingless bee (Partamona testacea) and the aggressive predator bullet ant (Paraponera clavata). In the study area, the colonies of P. testacea we spotted were all associated with P. clavata or Atta sp. ants. COI mitochondrial gene sequences of bees associated with bullet ants and leafcutter ants did not show any divergence, thus revealing no evidence that the two nesting strategies represent a case of cryptic speciation and specialisation on specific hosts. Bees are not unarmed respect to the bullet ants; when ants attempted to penetrate in the colony entrance, they were dragged inside the nest and covered by a resin-like substance. Behavioural experiments focused on ants in arenas and focused on bees at their nest entrance proved that the ants are significantly less aggressive toward associated bees and that guard bees are less alarmed when associated ants are presented. We verified by Gas Chromatography and Mass Spectrometry that P. testacea maintains its species-specific cuticular signature in the association with different ant species and that ants and bees possess typical colony signatures. The differential behavioural responses expressed toward associated colony members by both species are likely based on learning these heterospecific cuticular signatures as it occurs in ant parabiotic associations.