Location: Crop Production and ProtectionTitle: Where do adaptive shifts occur during invasion A multidisciplinary approach to unravel cold adaptation in a tropical ant species invading the Mediterranean zone) Author
Submitted to: Ecology Letters
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/17/2012
Publication Date: 10/1/2012
Citation: Olivier, R., Estoup, A., Vonshak, M., Loiseau, A., Blanchet, S., Rossi, J., Kergoat, G.J., Foucaud, J., Orivel, J., Calcaterra, L., Chifflet, L., Courtoisier, P., Leponce, M., Schultz, T., Facon, B. 2012. Where do adaptive shifts occur during invasion A multidisciplinary approach to unravel cold adaptation in a tropical ant species invading the Mediterranean zone. Ecology Letters. DOI:10.1111/j.1461-0248.2012.01849.x. Interpretive Summary: Evolution is widely recognized as playing an important role in improving the success of pests and weeds. Key evolutionary changes, necessary for the establishment and invasion of new biogeographic regions, may occur within the native range under particular conditions before long-dispersal events into new regions or in the region where the organisms were introduced. The little fire ant (Wasmannia auropunctata) is a good candidate species to investigate where key evolutionary changes occur during the invasion process. Some populations of the little fire ant have recurrently and successfully colonized human-modified habitats within their homeland (e.g. urban areas, some plantations), where they become ecologically dominant. Workers from these populations established in human-modified habitats showing a higher tolerance to the hotter and dryer conditions than populations occurring in native forests. In 1998, established populations of the little fire ant were found in Israel, a region with much colder temperature than the tropics. The two main goals of the present study were to investigate whether the establishment of the little fire ant in Israel was effectively accompanied by an adaptation of ants to cold temperature and to assess whether this adaptation occurred in its native land or after transportation to Israel. This study revealed that Israeli populations of the little fire ant are more adapted to cold temperatures than tropical populations, and that this adaptation to cold presumably occurred in the southern edge of the natural distribution in Argentina before being introduced accidentally into Israel.
Technical Abstract: Although evolution is now recognized as improving the invasive success of populations, where and when key adaptation event(s) occur often remains unclear. Here we used a multidisciplinary approach to disentangle the eco-evolutionary scenario of invasion of a Mediterranean zone (i.e. Israel) by the tropical ant, Wasmannia auropunctata. Laboratory experiments reveal that Israeli populations are more adapted to cold temperatures than tropical native and invasive populations. Species distribution modelling indicates that adaptation to cold temperature conditions typical of Israel potentially occurred in Florida and in the southern edge of the native range (north-eastern Argentina). Phylogeographic analyses based on mitochondrial and microsatellite DNA indicate that the Israeli populations were loosely related to Floridian ones but were remarkably similar to populations from Argentina. Altogether, our results strongly suggest that Israeli populations followed a two step invasion scenario with prior adaptation to cold having occurred in north-eastern Argentina before long distance dispersal into Israel.