The invasive tawny crazy ant, Nylanderia fulva, in the south limit of its native distribution range

FERNÁNDEZ, M. B.; SÁNCHEZ RETREPO, A. F.; VARGO, E.; JOHNSON, L.; SHOEMAKER, D. D.; CONFALONIERI, V.; CALCATERRA, L. A.

Curitiba, Paraná, Brasil

Simposio; XXIII Simpósio de Mirmecología, An International Ant Meeting; 2018

Universidad Federal de Paraná

Ants comprise 5% of the world?s 100 worst invasive species. Increasing global commerce facilitates their distribution throughout the world; such is the case of the tawny crazy ant (TCA), Nylanderia fulva, introduced into the US in 2002 from an unknown site within its native southern South America. TCA is a major urban and ecological pest that has dispersed throughout Texas, Florida, and southern Louisiana and Mississippi. Recent studies in the Gulf Coast of Texas showed that the TCA quickly reaches densities of up to two orders of magnitude greater than all other ant species pooled together, likely due to its strong poison and supercolonial social structure across southern US; yet nothing is known about TCA in its native range. The objectives of this study are to know the distribution of TCA in Argentina, the putative source population introduced into the US, using a COI marker of 794 pb; to investigate its social structure using paired tests of aggression between nests; and to infer its reproduction system (sexual or clonal), using microsatellite markers. Initial surveys were mostly concentrated in northeastern Argentina. Samples of workers, alates and/or queens were collected for behavioral assays and molecular analyses. TCA nests were found across the entire surveyed area. As observed in populations in the US, native populations did not show evidence of aggressive behavior between nests at the local scale. COI sequences from the native range were compared with published sequences from the US. As expected, the number of COI haplotypes in the native range was several times higher and more diverse than in the US. A Neighbor Joining Distance Tree recovered three haplogroups. All introduced populations grouped in a single haplogroup in which a haplotype from Misiones, Paraguay, and Brazil was similar to a haplotype found in Texas and Louisiana, and a haplotype from Entre Ríos was similar to a haplotype from Florida and Texas, and closely related to the haplotype from US Virgin Islands. These findings suggest the introduction could have originated from northeastern Argentina and/or from nearby areas of Paraguay and Brazil. Colonies found in Argentina appear to have much lower numbers of queens than colonies in the US. Population genetic analysis from Argentine populations revealed differences in allele frequencies: queens were homozygous in more loci than workers, which were mostly heterozygotes. These unusual genotype frequencies could have resulted from a combination of sexual and clonal reproduction, as in other highly invasive ants. (CONICET, PICT-FONCyT, ARS-USDA, Texas A&M University)