|
Matt Walker
Editor, Earth News
|
A queen and worker Argentine ant have many, many relatives
A single mega-colony of ants has colonised much of the world, scientists have discovered. Argentine
ants living in vast numbers across Europe, the US and Japan belong to
the same interrelated colony, and will refuse to fight one another. The
colony may be the largest of its type ever known for any insect
species, and could rival humans in the scale of its world domination. What's more, people are unwittingly helping the mega-colony stick together. Argentine ants (Linepithema humile) were once native to South America. But people have unintentionally introduced the ants to all continents except Antarctica.
These
introduced Argentine ants are renowned for forming large colonies, and
for becoming a significant pest, attacking native animals and crops. In
Europe, one vast colony of Argentine ants is thought to stretch for
6,000km (375 miles) along the Mediterranean coast, while another in the
US, known as the 'Californian large', extends over 900km along the
coast of California. A third huge colony exists on the west coast of
Japan.
While ants are usually highly territorial, those living within each
super-colony are tolerant of one another, even if they live tens or
hundreds of kilometres apart. Each super-colony, however, was thought
to be quite distinct. But it now appears that billions of Argentine ants around the world all actually belong to one single global mega-colony. Researchers
in Japan and Spain led by Eiriki Sunamura of the University of Tokyo
found that Argentine ants living in Europe, Japan and California shared
a strikingly similar chemical profile of hydrocarbons on their
cuticles. But further experiments revealed the true extent of the insects' global ambition. The
team selected wild ants from the main European super-colony, from
another smaller one called the Catalonian super-colony which lives on
the Iberian coast, the Californian super-colony and from the
super-colony in west Japan, as well as another in Kobe, Japan. They
then matched up the ants in a series of one-on-one tests to see how
aggressive individuals from different colonies would be to one another.
Ants from the smaller super-colonies were always aggressive to
one another. So ants from the west coast of Japan fought their rivals
from Kobe, while ants from the European super-colony didn't get on with
those from the Iberian colony. One big family But
whenever ants from the main European and Californian super-colonies and
those from the largest colony in Japan came into contact, they acted as
if they were old friends. These ants rubbed antennae with one another and never became aggressive or tried to avoid one another. In
short, they acted as if they all belonged to the same colony, despite
living on different continents separated by vast oceans. The
most plausible explanation is that ants from these three super-colonies
are indeed family, and are all genetically related, say the
researchers. When they come into contact, they recognise each other by
the chemical composition of their cuticles. "The enormous
extent of this population is paralleled only by human society," the
researchers write in the journal Insect Sociaux, in which they report
their findings. However, the irony is that it is us who likely
created the ant mega-colony by initially transporting the insects
around the world, and by continually introducing ants from the three
continents to each other, ensuring the mega-colony continues to mingle.
"Humans created this great non-aggressive ant population," the researchers write. | 
E-mail this to a friend
Printable version
The enormous extent of this population is paralleled only by human society
