Castro-Cobo, S., Blight, O., Espadaler, X. & Angulo, E.

Long-term spread of Argentine ant (Hymenoptera: Formicidae) European supercolonies on three Mediterranean islands

The Argentine ant is an invasive species that has spread all over the world and is organized in several supercolonies. While there are many studies about factors promoting the expansion of the species, little is known about the factors affecting the variation in spread among the different supercolonies. We examined the environmental and spatial variables affecting the invasion of the Argentine ant on three islands of the Mediterranean Sea (Corsica, Ibiza, and Formentera) and in the three European supercolonies that inhabit them (Main European, Corsican, and Catalonian). We used data from two sampling periods, nine years apart in the case of Corsica and 12 years in the case of Ibiza and Formentera, coupled with historical data of first detection dates and locations on islands of Southwestern Europe. Along the coast of the three islands, we sampled each beach to detect the presence of the Argentine ant and used aggression assays to identify the supercolony they belonged to. The Argentine ant expanded its range on all three islands. Although the three supercolonies maintained their same locations and expanded to new locations, the highest expansion for the Main Supercolony was on Ibiza and Formentera and for the Corsican Supercolony on Corsica. Interestingly, the Argentine ant did not dominate at all our study sites. On one third of the beaches of Ibiza and Formentera, it co-occurred with native ant species even after 12 years. Human presence affected the likeliness of a beach to be invaded on Ibiza and Formentera. On Corsica, beaches that had already been invaded before our study or were invaded during our study were the ones with lower distance to already invaded beaches, suggesting the importance of secondary introductions in the local expansion of the Argentine ant. Our findings help to understand the dynamics of invasions of the Argentine ant and its different supercolonies. Long-term studies at many invaded sites are of great importance in order to obtain general patterns of the spread of this global invader.

Open access, licensed under CC BY 4.0. © 2021 The Author(s).

Castro-Cobo, S., Blight, O., Espadaler, X. & Angulo, E.

Long-term spread of Argentine ant (Hymenoptera: Formicidae) European supercolonies on three Mediterranean islands

The Argentine ant is an invasive species that has spread all over the world and is organized in several supercolonies. While there are many studies about factors promoting the expansion of the species, little is known about the factors affecting the variation in spread among the different supercolonies. We examined the environmental and spatial variables affecting the invasion of the Argentine ant on three islands of the Mediterranean Sea (Corsica, Ibiza, and Formentera) and in the three European supercolonies that inhabit them (Main European, Corsican, and Catalonian). We used data from two sampling periods, nine years apart in the case of Corsica and 12 years in the case of Ibiza and Formentera, coupled with historical data of first detection dates and locations on islands of Southwestern Europe. Along the coast of the three islands, we sampled each beach to detect the presence of the Argentine ant and used aggression assays to identify the supercolony they belonged to. The Argentine ant expanded its range on all three islands. Although the three supercolonies maintained their same locations and expanded to new locations, the highest expansion for the Main Supercolony was on Ibiza and Formentera and for the Corsican Supercolony on Corsica. Interestingly, the Argentine ant did not dominate at all our study sites. On one third of the beaches of Ibiza and Formentera, it co-occurred with native ant species even after 12 years. Human presence affected the likeliness of a beach to be invaded on Ibiza and Formentera. On Corsica, beaches that had already been invaded before our study or were invaded during our study were the ones with lower distance to already invaded beaches, suggesting the importance of secondary introductions in the local expansion of the Argentine ant. Our findings help to understand the dynamics of invasions of the Argentine ant and its different supercolonies. Long-term studies at many invaded sites are of great importance in order to obtain general patterns of the spread of this global invader.

Open access, licensed under CC BY 4.0. © 2021 The Author(s).