We are used to imagining a colony of ants like a small one anthill with a single queen, but in reality some species live in Very large colonies distributed between numerous interconnected nests. Many queenclosely related to each other, they can coexist in a single colony, and the workers take care of them without making distinctions. The extensions of these supercolonies sometimes reach the hundreds of km2 and a huge number of individuals. In the 1971 A colony of Formica Yessensis with 300 million workers and more than 1 million queens, divided into 45 Ooo Nidi!
But there is a species, the Argentina formica (Linepithema humile), in which colonies can reach proportions continentaltaking advantage of human commercial networks and invading the habitat of native ants. In 2000 the researchers of the University of Lausanne and of Copenhagen They started an analysis work that lasted two years on 33 colonies of Argentine ants, hundreds of kilometers away. By comparing them through specific tests, they actually understood that they were faced with anThe only colossal supercolonia. This follows the Mediterranean coastal line starting from Liguria, passing from the south of France and Spain, runs through the entire Atlantic bank of Portugal to finally get to Galicia. The overall extension is of over 6 000 kmwith millions of nests, tens of millions of queens e billion of workers: the record of Hokkaido’s anthill had been demolished.
How to understand if two ants belong to the same colony
You can make test To verify its proximity genetics: the ants of the same ant they are all sisters with each other and therefore present a very similar genome. Or you can do the so -called aggression test: if two ants attack each other, it means that they belong to different colonies. Each ant, in fact, brings with it a sort of “Odorous label”, Genetically determined and shared with the members of the same colony. When he meets a Unclossed smell Take the attack mechanismeven between two ants of the same species but of different colonies.
This aggressiveness unleashed by the smell allowed researchers of the study to compare the colonies of Linepithema humile. Individuals of the Italian ones, in fact,, they did not show any aggression if put next to individuals of the French, Spanish and Portuguese colonies. An ant withdrawn from a Ligurian colony and brought to the Galitian one will continue to behave as before inside the anthill, and nobody would notice the difference. Only the colony Catalanamong the 33 analyzed, it was genetically distinguished and showed clear aggression towards the others.
The evolutionary origin of ants supercolonies
A supercolonia is a rarity between the ants: between the 14 000 known species, those that live in Supercolonie I am less than 1%. Why the Linepithema humile Do you make such gigantic colonies, and why in Europe? As can be guessed by the name, the Argentine ant is one invasive species, Among the 100 considered most dangerous for biodiversity by International Union for Conservation of Nature. Is originally from South Americawhere his behavior and social structure are more similar to the standards of other species of ants. Exploiting the human commercial networks He colonized the rest of the world in a short time: few individuals transported by chance aboard the ships they reached distant lands and reproduced very quickly.
This explains the genetic proximity of the European Supercolonia with the overseas sisters: the “bottleneck” effect, a well -known biological evolution mechanism, produces one population with very similar genetic characteristics, as inherited from a small number of progenitors. This homogeneity is probably also the secret of their success: since they are not in competition with each other they have supplanted the other species of ants with ease, occupying the related ecological niches. In fact, the Argentine ant has the tendency to expand up to occupy all available spaceand it can also end up infesting urban areas and homes. Almost all the species that form supercolonies are in turn invasive.
A single global megacolonia
Supercolonie di Formica Argentina, although not so large, are also found in Japan and in California. The dispersion mechanism of this species led researchers to hypothesize that individuals of these supercolonies were very similar to each other. The researchers of theUniversity of Tokyo they managed to demonstrate it in 2009 through genetic analysis and aggressive tests: all three supercolonies would in fact make part of the same intercontinental megacolonia. It would be, in this case, of the larger organized animal society On the planet Earth, second only to the human species by number of individuals.
