First report on the use of Stryphnodendron adstringens (Fabaceae) live fruits as nests by Camponotus sp. and Nesomyrmex spininodis (Hymenoptera: Formicidae) in a Neotropical savanna

Ant–plant mutualism is widespread and highly diverse in the Neotropics. Several species of arboreal ants can utilize plants as nesting site by colonizing domatia or preformed cavities in tree trunks, branches, and stems that have been perforated by wood-boring insects. Arboreal cavity-dwelling ants are a common occurrence, and its effects are well documented, the most studied of which is protection against phytophagous insects. Despite the diversity of cavities in which ants can nest, there are only four published records of colonies inside fruits still attached to trees. Here, we report the occurrence of ant colonies inside mature fruits of Stryphnodendron adstringens , which to our knowledge comprises the first formal record of fruit nests at the Brazilian Cerrado, a Neotropical savanna. We encountered five fruits colonized by Camponotus sp. and one by Nesomyrmex spininodis . Most fruits housed both adult workers and immature ants, except for one fruit that was occupied solely by workers and was attached to the same tree as another that contained larvae. That, and the fact that we did not find any queen, suggest these are polydomous nests. We discuss the possible implications of this association and the knowledge gaps regarding this scarcely studied interaction.