From insinuator to dominator: Foraging switching by an exotic ant

Abstract

Aim: Understanding the ecological conditions that determine invasive success requires information on the ecological dynamics in both the native and introduced range of exotic species. While numerous studies of the little fire ant, Wasmannia auropunctata, have focused on the evolutionary aspects of invasiveness, we know little about possible ecological dynamics that might contribute to the remarkable invasiveness of this species. Location: We investigate the ecological differences in resource discovery and recruitment by W. auropunctata within its native range (Mexico) and introduced range (Puerto Rico). Methods: We conducted experimental trials on coffee plants by comparing: (1) the rate of resource discovery by W. auropunctata at various distances from main foraging trails; and (2) the recruitment rate between W. auropunctata in the introduced range of Puerto Rico. Results: Our experiments revealed that W. auropunctata took nearly twice as long to discover baits in Puerto Rico, as compared to Mexico. W. auropunctata was relatively slower at recruiting workers than other dominant ants. Main conclusion: We conclude that competitive traits such as resource discovery and recruitment are not necessarily indicative of invasive success, but contradict traditional expectations. We propose that W. auropunctata behaves as an insinuator species in Mexico (i.e. workers maintain a low profile), while in Puerto Rico it acts as an aggressive dominator. The switch in foraging strategy might explain the astounding success of this exotic species.