BayCEER Workshop 2016

Distribution and colony fragmentation of the invasive ant Anoplolepis gracilipes on La Réunion

Biological invasions are considered to be a great threat to biodiversity and ecosystems. The yellow crazy ant, Anoplolepis gracilipes, is amongst the 100 worst invasive species worldwide. Similar to other invasive ant species A. gracilipes forms supercolonies where a large number of nests are spread over a large area, sometimes up to thousands of square-kilometres. Nevertheless, ants from different nests of one supercolony will typically show non-aggressive behaviour against each other, have a high genetic similarity and share a similar cuticular hydrocarbon profile for nestmate recognition. In this work, the population of A. gracilipes on La Réunion was investigated for its supercolony structure combining genetic, chemical and behavioural methods. The population genetic analyses revealed a high similarity between all sampled nests, which was likewise found in the chemical analysis of the cuticular hydrocarbon profiles. Consequently, the behavioural assays did not reveal a clear discrimination among workers from different nests of A. gracilipes spread over the whole island. These results suggest that there is only a single supercolony of A. gracilipes on La Réunion. Combining the genetic data of A. gracilipes on La Réunion with a worldwide dataset suggests an introduction of A. gracilipes on La Réunion due to human activities as A. gracilipes on La Réunion had a high similarity to A. gracilipes supercolonies from different, geographically distant regions. In light of the likely further future introduction events of A. gracilipes La Réunion might be ideally suited to study the development of a new supercolony of A. gracilipes next to an already existing one. Otherwise, as the fragmentation of one A. gracilipes supercolony into several distinct, separate supercolonies has been observed, A. gracilipes on La Réunion might also provide the unique opportunity to study the supercolony-fragmentation of an invasive ant species in real time.