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Thomas Lado, in the field preparing to collect ant specimens.

The Argentine ant is arguably one of the best-studied invasive species, perhaps as a result of the significant economic concerns and scale of its invasion. This native South American species has invaded Mediterranean-type ecosystems worldwide and has successfully become established on all continents (excluding Antarctica) and numerous Oceanic islands.

Unraveling some of the history for the introduction of Argentine ants into South Africa forms part of Thomas Lado’s PhD study done under the supervision of Prof. Steven Chown and Dr. Bettine van Vuuren. Interestingly, across their native range in Argentina and Brazil, Argentine ants display a multi-colonial social structure with aggression between workers of different nests. This is in sharp contrast to the large super colonies that form in areas where Argentine ants are invasive.
Researchers (Tsutsui et al. 2001, Molecular Ecology, 10: 2151-2161) have convincingly shown that most of the invasive colonies world-wide are genetically very similar and trace their source of introduction back to localities along the Rio Parana (South America). Their study included Argentine ants sampled from three localities in South Africa (Betty’s Bay, Cape Point and Caledon). These South African localities were genetically the most distinct introduced populations, with ants from Caledon being more similar to ants from Buenos Aires.
This may indicate at least two introductions for the Argentine ant into South Africa. Given that only 15 Argentine ants from South Africa (five per locality) were included in the earlier study, the researchers at the DST-NRF Centre of Excellence for Invasion Biology are interested in whether they can find supporting evidence for multiple introductions into South Africa based on a much larger and more comprehensive data base. Their study includes more than 160 ants sampled from localities throughout South Africa.