Linepithema humile (Mayr) – Mrówka argentyńska

The information contained in the Alien Species in Poland database is purely scientific and does not constitute legal advice or carry legal authority.

Status

The species is alien in whole area of its current or past occurrence in Poland

Currently present indoors

Reproducing indoors

Non invasive alien species

General charactreristics

Description and biology

Males differ from females. Omnivorous. In South America, L. humile is known as “sugar ant” because of its preference for carbohydrate food like nectar or honeydew. This is related to a negative impact in newly colonised areas, as the ants effectively protect the honeydew producers; Coccids and aphids (sources of honeydew), against their natural enemies, and therefore L. humile contributes to damage in agriculture. On the other hand, egg-laying queens and growing larvae of L. humile demand protein-rich food, and predation is the main way to satisfy this need. For example, in Australia, the Argentine Ant destroys up to 80% of termite nests in the controlled area. Linepithema humile, the Argentine Ant, is a South-American species. Due to human activity, it has spread to the subtropical and temperate zones of all the continents and oceanic islands. It forms polygynous societies (even more than 100 queens to a nest), capable of developing into polycalic (multi-nest) systems that constitute networks of mutually connected colonies. Its native range is in the tropical and subtropical forests of South America (northern Argentina, Uruguay, Paraguay, southern Brazil). In the native range, individual polycalic colonies of the Argentine Ant are relatively small – both in respect to the number of nests and occupied area. Usually they occupy there an area of up to a few hundred square meters. Development of the colonies is limited by neighbour alien colonies of the same species. Foreign societies of L. humile are competitive towards each other, and treat their conspecific neighbours in a hostile manner. Only males take part in a nuptial flight, searching for distant colonies, where gynes await them. Mating is intranidal, and newly inseminated young queens fly out, but not farther than 100 m. They establish new colonies outside the maternal society, or are adopted by other colonies within their own polycalic system. At the beginning of the 20th century, together with trade and transport development, the Argentine Ant was introduced to Europe, North America, Africa and Asia, where it occurs outdoors along the oceanic and sea coasts. In these new regions, it occurs mainly in cultivated fields, orchards and other anthropogenic habitats (including urban green areas). But it also occurs in different forests, including natural ones, e.g. Mediterranean oak forests. On newly occupied areas, in conditions where there is a lack of intraspecific competition, and where they are free from natural enemies, L. humile obtains much higher expansion possibilities than within its original range. Entire populations of the Argentite Ant may take on the form of one polycalic colony (so called supercolony), consisting of millions of nests occurring in enormous density, and covering hundreds or even thousands of square kilometres. The most spectacular example of such a structure is the South-European population which stretches out along the Mediterranean coast from northern Italy, through France and Spain, and farther along the Atlantic coast of Portugal to south-western Spain. A natural obstacle which prevents the population from spreading deep into the mainland, is climate. Farther than 10 km from the coast it is too dry for L. humile. Similar populations occur on the coast of California, and the western coasts of Japan and Australia. The decisive factor that favour creating such vast colonies on new areas, compared to the natural species range, is the radical reduction of intraspecific aggression. The latter is an effect of the seriously decreased genetic variability within introduced populations, which come from a few queens only. Decreased genetic variability of workers can lead in turn to a reduced ability to discriminate between nestmates and foreign homospecific individuals. A recent genetic survey of the huge European Mediterranean-Atlantic population proved that in fact it only consists of two supercolonies. One of the colonies is bigger, and spread over almost all of the populated area. The other colony is smaller, insularly placed within the area of the bigger one, in Catalonia (Spain). Ants representing both these supercolonies are hostile towards each other. In interspecific interactions, L. humile is very aggressive and highly competitive. In newly occupied territories, abundance of the Argentine Ant is incomparably higher than within the species’ original range. Due to this, the newcomers are a serious threat to native myrmecofaunas. Locally they are able to exterminate all heterospecific ants, including key-stone species crucial to the functioning of biocoenoses, like e.g. pollinators and seed carriers. Supercolonies increase their sizes by colony splitting; they can elongate in a rate of 270 m per year. This rate may be accelerated by human activity (e.g. transplantation of plants), animals and even flood events.

Impact on native biodiversity and local economy

Mechanisms of impact

• Competition

References

• Aron, S. 2001. Reproductive strategy: an essential component in the success of incipient colonies of the invasive Argentine ant Insectes Sociaux 48: 25–27. link
• Giraud, T., Pedersen, J. S., and L. Keller 2002. Evolution of supercolonies: The Argentine ants of southern Europe Proceedings of the National Academy of Sciences of 99: 6075–6079. link
• Hee, J., D. A. Holway, A. V. Suarez, and T. J. Case 2000. Role of propagule size in the success of incipient colonies of the invasive Argentine ant Conservation Biology 14: 559–563. link
• Holway, D. A 1998. Effect of Argentine ant invasions on ground-dwelling arthropods in northern California riparian woodlands Oecologia 116: 252–258. link
• Holway, D. A 1999. Competitive mechanisms underlying the displacement of native ants by the invasive Argentine ant Ecology 80: 238–251. link
• Holway, D. A., A. V. Suarez, and T. J. Case 1998. Loss of intraspecific aggression in the success of a widespread invasive social insect Science 283: 949–952. link
• Holway, D. A., and T. J. Case 2000. Mechanisms of dispersed centralplace foraging in polydomous colonies of the Argentine ant Animal Behaviour 59: 433–441. link
• Holway, D. A., and T. J. Case 2001. Effects of colony-level variation on competitive ability in the invasive Argentine ant Animal Behaviour 61: 1181–1192. link
• Human, K. G., and D. M. Gordon 1997. Effects of Argentine ants on invertebrate biodiversity in Northern California Conservation Biology 11: 1242–1248. link
• Tsutsui, N. D., and T. J. Case. 2001. Population genetics and colony structure of the Argentine ant (Linepithema humile) in its native and introduced ranges Evolution 55: 976–985. link

Author(s): Wojciech Czechowski, Piotr Ślipiński

Life form: Insect

Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae