Argentine ants Supercolonies: Trying to separate the inseparable

NURIA MORROW GALLI; CHLOÉ LEROY; ROXANA JOSENS; PATRIZIA D´ETTORRE

Luján de Cuyo, Mendoza

Congreso; X Congreso Argentino de Entomología (CAE); 2018

Facultad de Ciencias Agrarias. Universidad Nacional de Cuyo.

The Argentineant (Linepithema humile Mayr) is awell-studied invasive species. It commonly overexpresses polydomy - different nestsshow no aggression among them, thus establishing a supercolony. Supercoloniescan extend from hundreds of meters in their native range to thousands ofkilometers in the invasive range. The lack of intraspecific aggression isconsidered one of the key factors of their success as invaders. Aggressionoccurs when an ant recognizes the cuticular chemical profile of another ant as a non-nestmate. In this framework, weinvestigated (1) whether tree saturated methyl-branched hydrocarbons (CHs)could be incorporated into the cuticle through diet after a single ingestion;(2) whether the CHs that were effectively incorporated could triggeraggression; (3) the dynamics of incorporation of the CHs up to four days after the ingestion; and (4) whether thepresence of these CHs in the cuticle triggers a bias in food distribution.  Cuticleextracts were analyzed via GC-MS to evaluateCHs incorporations and their dynamics. To test whether these CHs could triggeraggression, aggression tests were performed between one treated and one untreatedant. Finally, food distribution tests were performed, confronting a fed donorwith five non-fed recipients, treated or untreated in all possible combinations.Multiple behavioral variables were analyzed, for donors and recipients. Wefound that all CHs were effectively incorporated into the cuticle 24 hoursafter ingestion. None of the CHs testedelicited aggression. All CHs were present on the cuticle four days after theingestion, and their quantities either stayed the same or dropped over time. Donorsbehave similarly when confronted either to treated or untreated recipients, andrecipients respond in a similar way to treated and untreated donors. Eventhough each CH was effectively incorporated into the cuticle within 24 hoursafter ingestion, and was still present four days after a single ingestion, its solepresence was not enough to modify workers? behavior. We thus conclude that the CHs tested in this study are not a key factoraffecting nestmate recognition or food-distribution behavior in L. humile.