Exotic Ants (Hymenoptera, Formicidae) Invading Mediterranean Europe: a Brief Summary over About 200 Years of Documented Introductions

Exotic ants have emerged as a relevant topic worldwide because of their remarkable impacts on native ecosystems and human activities. A first regional overview is given on the dozens of exotic ant species recorded in Mediterranean Europe since the end of the 19th century. About 39 exotic ant species, belonging to 17 genera and originating from 5 different biogeographical realms, are currently believed to be established in this region. The genera Nylanderia and Tetramorium are those hosting the larger proportion of species, while the Afrotropical realm is the prevalent source of taxa. According to the available data, France, Greece, Italy and Spain all host a high number of exotic species, which has increased at a dramatic rate during the last decades. On the other hand, Mediterranean countries on the Eastern part of the Adriatic Sea appear to be almost empty of exotic ants, perhaps due to both a lesser number of introductions and a lack of targeted investigations. Neighboring countries of the region do not necessarily have more species in common than those geographically distant. Very little is known on the intra-Mediterranean or intra-Palearctic introduction processes which probably occurred prior to the 19th century and on their influence on the current species distribution. The vast majority of the species that are actually established in the region are either restricted to indoor habitats or outdoor anthropogenic habitats, fewer of them were able to colonize semi-natural or natural habitats and very few are recognized as serious pests