International Union for the Study of Social Insects (IUSSI2018), August 5-10, 2018 in Guarujá, Brazil.

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Quantification of defensive compounds in the Argentine ant: does supercolony matter?

Author(s):
Paloma Alvarez-Blanco, Paloma Alvarez-Blanco , Isabel Salado , Raphael Boulay , Elena Angulo
Institution(s):
ESTACIÓN BIOLÓGICA DE DOÑANA - CSIC, SEVILLA, SPAIN; ESTACIÓN BIOLÓGICA DE DOÑANA - CSIC, SEVILLA, SPAIN ; ESTACIÓN BIOLÓGICA DE DOÑANA - CSIC, SEVILLA, SPAIN ; INSTITUT DE RECHERCHES SUR LA BIOLOGIE DE L'INSECTE-CNRS, UNIVERSITÉ FRANÇOIS RABELAIS, TOURS, FRANCE ; ESTACIÓN BIOLÓGICA DE DOÑANA - CSIC, SEVILLA, SPAIN
Unicoloniality is one of the main traits of invasive ants. It is based on the formation of supercolonies, large networks of polygynous nests lacking intraspecific competition but with high level of aggression with other supercolonies. Argentine ant supercolonies occupy hundreds of meters in the native range, where the expansion is limited by native species. In the introduced range, supercolonies reach higher densities and can spread thousands of meters. The so-called Main supercolony is spread from Portugal to France mainly through the coastline, while the Catalonian supercolony has a more restricted distribution.The origin and success of the supercolonies is still unclear and has focused on recognition approaches, involving genetic, chemical and behavioural studies. However, the role of pheromones, key features in social insects, has not yet been explored in this direction. Could the defensive compounds play a role in the supercolonies success? Iridomyrmecin is the major component of the Argentine ant and has been described mainly as trail or alarm pheromone, but also as defence allomone. Here, we pose for first time the hypotheses that the chemical weapons of the Argentine ant play a role in their invasiveness and help the main supercolony to spread more successfully than minor supercolonies.  We searched for differences in the amount of iridomyrmecin among supercolonies in the native range and two introduced supercolonies, Main and Catalonian. We found native supercolonies possess significantly higher quantities of iridomyrmecin than introduced supercolonies. Besides, the amount of iridomyrmecin varies within native supercolonies. However, we found no differences between the two introduced supercolonies, suggesting that the success of a given supercolony may not be explained by higher quantities of defensive compounds. New quantifications, including more compounds and other supercolonies should be done in order to fully understand the findings.
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