Ants are among the most diverse and successful organisms in terrestrial ecosystems. However, some species have become the worst invasive alien species and/or pest of the world. Increasing global commerce has facilitated their distribution to compatible habitats throughout the world. Interestingly, most of their invasions have originated from La Plata River basin in southern South America, as in the case of the invasive red and black fire ant (Solenopsis invicta and S. richteri), the Argentina ant (Linepithema humile) and the little fire ant (Wasmannia auropunctata), whose source populations were discovered in Argentina. Fortunately, these species are not a problem in their homeland. However, other native ants, such as leafcutter ants (Atta and Acromyrmex spp.), are major pests throughout the entire Neotropical Region. The main objective of our research is to reduce the ecological, economic impact and the global spread of invasive and/or pest ants through a multidisciplinary approach.
Little fire ant (Wasmannia auropunctata)
The little fire ant has become a pest not only in its native range (e.g. Colombia and Brazil), but also in new areas, invading the Caribbean and Pacific islands, subtropical Atlantic islands, the USA, and West Africa. Most of these regions have been invaded by a tropical lineage, except for West Africa, New Caledonia, Tahiti, and recently Israel. These areas were invaded by a mostly subtropical-temperate lineage, emphasizing its potential to invade non-tropical habitats. Little fire ant has been blamed for reducing ant species diversity, decreasing overall abundance of flying and tree-dwelling insects, and eliminating arachnid populations, as well as attacks on native reptiles, birds, and mammals. Intensive control efforts so far involve only toxic baits. To date, only one natural enemy is known: a micro-Hymenoptera parasitoid that was only found in Caribbean islands, Costa Rica, Colombia, Ecuador, Venezuela, Guiana, and Suriname, which is believed to be specific to the tropical lineage. However, the use of this parasitoid has been questioned because in regions where it is abundant its host ant is still very dominant; also because of the damage on plant leaves used as oviposition substrates. Consequently, there is an immediate need to find more effective agents or other factors that allow its control. The objectives of this project are (1) to focus the search for natural enemies in areas of greatest genetic diversity of subtropical-temperate lineage, (2) determine whether the two lineages are different cryptic species and (3) identify the main factors that determine its success as an invader in its introduced range.
Staff in charge:
Dr. Luis Calcaterra
Peter Follett, ARS-Pacific Basin Agricultural Research Center,
Hilo, Hawaii, EE.UU.
Viviana Confalonieri y Lucila Chifflet, Grupo de Investigaciones en Filogenias Moleculares y Filogeografía, FCEN-UBA.
Pablo Schilman, Profesor FCEyN-UBA; Investigador CONICET.
Fire ants have population densities in southern South America several times lower than those observed in their areas of introduction: southern USA, Puerto Rico and California, Arizona and New Mexico. They affect agriculture and wildlife and human populations causing economic damage(e.g. $6 billion/year in the USA). During the last decade, they have emerged as a global pest, with new infestations from the USA establishing in Australia, Taiwan, mainland China, Mexico, and many Caribbean islands. Self-sustaining parasites and pathogens from Argentina are being released to try to reduce fire ants populations to levels similar to those in South America where they are not considered an important problem. However, other factors such as their higher competitive ability, contribute also to their success as invaders. The objectives of this project are (1) to continue with the release of microsporidia and parasitoid flies from Argentina, (2) continuing the search for new pathogens using genomic tools, (3) study the evolution of supergene (Gp-9), which determines that a species possesses one (monogyny) or more (polygyny) queens per fire ant colony, and (4) performing a molecular phylogenetic analysis of South American parasitoid flies to know the relationships among species and define potential new cryptic species in order to select the most suitable fly genotype for the control of each fire ant pest.
Staff in charge:
Andrés Sanches Restrepo
R. Vander Meer, S. Porter, D. Oi, S. Valles, y D. Shoemaker, ARS-CMAVE, Gainesville, Florida, USA.
Chen, M. Grodowitz, ARS, BPRU, Stoneville, Mississippi, USA.
Leafcutter ants (Atta spp., Acromyrmex spp.)
The Neotropical leafcutter ants (Atta and Acromyrmex spp.) are part of the fungus-growing ant group. They are one of the main herbivores and one of most destructive insects in the Neotropics, causing losses in the order of several billions of dollars annually. Many crops are affected by defoliation of leafcutter ants, activity that affects the growth and survival rate of plantations. It has been reported that leafcutter ants attack young trees (seedlings) of less than 6 months old causing reductions of up to 32% of its height, 25% of circumference, and 60% of wood production. Despite the importance of leafcutter ants as forestry and vineyards pests, very little is known about their damage levels or factors that influence their preferences and intensity of defoliation. In addition, little is known about biogeography, ecology, genetics and physiology of most of the species in the Acromyrmex genus and their fungal gardens. The objectives of this project are (1) to study the geographical distribution, taxonomy, phylogenetic relationships, ecology and physiology of leafcutter ants in southern South America and (2) determine the damage levels of the most damaging leafcutter ant species in forest plantations and vineyards of Argentina and the main factors affecting their herbivory patterns within the framework of a local Project of Scientific and Technological Research (PICT-FONCyT), whose aimed is reducing leafcutter impact on the region.
Staff in charge:
Andrés Sanches Restrepo
Patricia Fernández, Facultad de Agronomía-UBA, CONICET y EEA INTA Delta.
Viviana Confalonieri y Lucila Chifflet, GIFF, FCEN-UBA, CONICET.
Pablo Schilman, Laboratorio de Ecofisiología de Insectos, FCEN-UBA, CONICET.
Emilse Amatta, Stella Giannoni, UNSJ, CONICET, San Juan.
Natalia Yela, Adriana Aranda-Rickert, Sebastian Fracchia, CRILAR, CONICET, La Rioja.
Irradiation treatment and bio-insecticides for control invasive ants
Involves studies on (1) radiation treatments of cargo to control stowaway invasive and (2) identification of defensive/offensive compounds (natural toxins) in ants for possible use in the management of invasive ants, most specifically the invasive fire ants and tawny crazy ants has been included among our projects. Specific goals are determine (1) the generic doses of ionizing radiation necessary to eliminate or make unviable stowaway invasive ant species (e.g. W. auropunctata, L. humile, S. invicta) in cargo without affecting quality of the shipment and (2) the chemical compounds with the highest repellency, toxicity (bio-insecticide), attractiveness activity that can impair fire ant and tawny crazy ants.
Low-dose ionizing radiation is used as a post-harvest treatment to control quarantine pests (e.g. invasive ants) in fresh agricultural commodities. Defensive/offensive secretions (natural toxins) of ants play an important role in determining the behavioral dominance of ants. Gamma radiation and natural toxins ant are currently two alternatives that are being used to replace the use of conventional insecticides to control invasive and/or pest ants. The objectives of this project are (1) to determine the generic dose of radiation to sterilize queens of the main invasive ants (e.g. W. auropunctata, L. humile, S. invicta) traveling as a stowaway on export products without affecting their quality and (2) discovering new chemical compounds produced by Poisson and Dufour glands with high repellency and toxicity activity in ants that coexist with invasive species in ant assemblages in southern south America to develop repellents and biosinsecticides against invasive and/or pest ants.