Print PageInvasive ants are among the most widespread and destructive invasive species, and their ecological impacts can be magnified when they receive energy-rich honeydew from hemipteran mutualists (e.g. aphids). However, much remains unknown about how these energy subsidies fuel colony growth shortly after introduction, when propagules are small and the loss of even a few workers can be fatal. Aphid mutualists often support dense and ecologically dominant populations of the invasive Argentine ant, Linepithema humile. However, because small Argentine ant propagules are poor competitors, resources from aphids may be even more important during the initial establishment phase. We used laboratory experiments to examine how aphid-derived resources shape life history and behavioral traits necessary for colony establishment. We also examined whether the absence of alternate prey, the availability of protein relative to carbohydrates in synthetic diets, or the presence of developing brood, causes small ant propagules to prey upon aphids for the protein in their body tissue.
Results/Conclusions
Aphid mutualists enhanced all measured life history traits related to colony establishment, even at low densities, and even in the absence of supplemental prey items. In addition, aphid populations grew rapidly, even when colonies were otherwise starved of protein, and even when they had developing brood to feed, suggesting that ants consume carbohydrate-rich honeydew, rather than protein from aphid body tissue. Finally, behavioral experiments and nutrient analyses of ant body tissue suggest these aphid-derived resources are used by colonies to fuel colony growth rather than higher worker tempo. In sum, while massive supercolonies of invasive ants are often associated with hemipteran-derived resources, our results provide insights into how aphid mutualists allow propagules to overcome the long odds of colony establishment, and thus proceed towards numerical dominance over native ant fauna.
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