D3299: Enforcement of mutualism by a root mealybug tending ant (genus Acropyga)

Trophobiosis, where ants protect various organisms from predators and parasites in exchange for food, is an important aspect of ant ecology that has had evolutionary implications for both ants and their trophobiotic partners. The ant genus Acropyga engages in a unique form of trophobiosis by maintaining herds of root-feeding mealybugs (Rhizoecidae and Xenococcidae) within their nests. These ants likely rely entirely on the mealybugs’ secretions for sustenance. A striking aspect of this mutualism is a behavior known as trophophoresy, in which virgin Acropyga queens carry a gravid female mealybug from their home colony during their nuptial flight. Whether future mealybugs are produced clonally or sexually is unknown. In this way, trophophoresy likely serves as the lynchpin that stabilizes the mutualism by giving the ants direct control over the mealybugs’ dispersal and reproduction. Therefore, the ants may be able to apply selective pressure for favorable mealybug phenotypes. To test the efficacy of trophophoresy in controlling mealybug dispersal, we will analyze the average inbreeding coefficients (F) of mealybugs from 20 colonies from Barro Colorado Island, Panama. We hypothesize that nestmate mealybugs will show an average F value close to 1, indicating primarily asexual reproduction and, by extension, significant ant control over mealybug dispersal.