The Little fire ant in Argentina: New contributions to its distribution, social organization, and phylogeography

CHIFFLET, LUCILA; CALCATERRA, LUIS; CONFALONIERI, VIVIANA; REY, OLIVIER

Petrópolis, Rio de Janeiro

Simposio; XX Simposio de Mirmecología y I Encuentro de Mirmecólogos de las Américas; 2011

Native to the Neotropics, the little fire ant (LFA), Wasmannia auropunctata, has emerged in the last century as a major exotic pest that could easily be in the early phases of a pantropical explosion. This tramp ant has been spread by global commerce invading several Atlantic and Pacific islands, southeastern USA, western Africa and it was recently registered in Israel, which is raising concerns about its potential distribution outside the Tropics. Although numerous studies were conducted on LFA populations in northern South America, very little is known about populations in the southern limits of its native range. The objectives of this work were to make a preliminary phylogeographic analysis of the Argentinean LFA populations by PCR amplification of the COI mitochondrial gene, to study its social organization using aggression assays, and to determine its reproductive system (sexual or clonal) using microsatellite markers. An exhaustive survey was made through northern and central-eastern Argentina. The finding of LFA in the Puna ecosystem at 2,125 m of altitude, under extremely cold and dry conditions, represents the highest altitude reported so far for this species. Dominant clonal populations with unicolonial organization were found in human perturbed areas in central and northwestern Argentina, while non dominant (clonal or sexual) populations with a multicolonial organization were found in natural habitats (native forests) in northeastern Argentina. The supercolonies found were much smaller than those reported for the introduced range. Microsatellite data indicate that LFA in Israel was introduced from a population from the Zárate floodplain in Argentina. A total of 17 haplotypes were found, and, according to the haplotype network, LFA suffered a recent spatial expansion in Argentina. The haplotype in Zárate and Israel derived from a very widespread haplotype in Argentina, which derived from another haplotype that was only found in the Puna. Invasive populations in Israel might have suffered a pre-adaptation to cold temperatures and dry climate in northwestern Argentina, may have arrived to Buenos Aires, and accidentally transported to Israel. To test these hypotheses we will have to increase the robustness of the phylogeographic analysis including new genes and additional populations from southern South America. We will also have to make ecological and population genetic studies comparing Argentinean and Israeli populations to further confirm a two step invasive scenario in the evolutionary history of the LFA.