The untold story of Linepithema humile

RODRIGO POL; CAROLINA PARIS; ADRIANA RICKERT; MAKI INOUE

Curitiba

Simposio; XXIII Simposio de mirmecología; 2017

In the last 37 years the invasive ant, Linepithema humile, was extensively studied outside their native area, the Parana-Uruguay river basin. However, little is known about its spread and establishment in localities close to their native area. Our aims were: 1. to update the distribution of L. humile introduced population along to Argentina; 2. to examine their population structure in relation to other worldwide introduced populations and; 3. to assess the relation between aggressive behavior among colonies and its geographic distance. DNA was extracted from 96 L. humile workers of colonies from native and introduced localities of Argentina. Then a 1700-bp partial sequence from the cytochrome c oxidase subunits I (COI) and II (COII) and cytochrome b genes were amplified. Maximum-parsimony tree was constructed including worldwide populations and L. oblongum sequences as outgroup taxa. Aggressive behavior was categorized at five levels. Scores above two were regarded as aggressive behaviors. New and previously reported introduced populations were found at eight provinces of Argentina (Jujuy, Salta, La Rioja, San Juan, Mendoza, La Pampa, south of Buenos Aires and Chubut). The sequences of amplified mtDNA revealed that the Argentinian and worldwide populations are divided into two genetically distinct clades. One haplotype included some supercolonies of Japan, the main European (main clade), most of native Argentinian populations, and three introduced populations at vineyards of Mendoza (Argentina). The other clade consisted of four native populations, most of introduced populations at desert areas transformed into vineyards (Mendoza, Salta), orchads (La Rioja) or urban areas (La Pampa, south of Buenos Aires and Chubut), and minor introduced supercolonies from Tokyo, Kobe C and Catalonia). The genetic data were inconsistent with the behavioral test, since some native colonies of the main clade developed aggressive behavior among them. The mean level of aggressive behavior among populations from native area was lower than that showed by introduced populations and between native and introduced populations. There was no significant linear relationship between aggressive behavior level and distance among locations of native and introduced populations. Therefore, within Argentina, those L. humile populations that belong to the main clade are widely distributed along the coastal areas and facilitating its transportation to other regions of the world. In addition, other haplotypes established successfully at islands and desert regions of Argentina. Our results raise the question about how often are introduced populations transported to the native area and which are the ecological consequences of these reintroductions.