Convergent evolution of levee building behavior among distantly related ant species in a floodplain ant assemblage.

Flooding impacts ground nesting ant colonies by destroying the infrastructure housing and organizing societal function. Here, we report the convergent evolution in distantly related ant species of a behavioral trait that minimizes costs of flooding: the construction of earthen levees around nest entrances. In a South American floodplain ecosystem, we observed five ant species constructing prominent earthen berms encircling nest entrances shortly after large rainfall events. In four of these species, experimental flooding of nests demonstrated that earthen berms sufficed to prevent floodwaters from entering the below ground portions of the nest. Additional manipulations revealed that levee breaching caused, pronounced, and extended reductions in food collection for two distantly related species. Foraging was preempted by the allocation of workers to repair the internal structure of the nest. These findings represent convergent evolution of a functionally important nest construction behavior in response to comparable selective forces.