Ant invaders eat the natives, then move down the food chain

[C1ay]

The Argentine ant, Linepithema humile, is one of the most successful invasive species in the world, having colonized parts of five continents in addition to its native range in South America. A new study sheds light on the secrets of its success.

 

lefthttp://hypography.com/gallery/files/9/9/8/argentine_ants_thumb.jpg[/img]The findings, from researchers at the University of Illinois and the University of California at San Diego, appear this week in the Proceedings of the National Academy of Sciences.

 

The Argentine ant is tiny, aggressive and adaptable, traits that have helped it in its transit around the world. Once seen only in South America, the ant is now found in parts of Asia, Australia, Europe, North America and South Africa. It most likely made its way to these destinations on ships carrying soil or agricultural products.

 

Under the right conditions, the Argentine ant marches through a new territory, wiping out - by eating and out-competing - most of the native ants and many other insects. In the process it radically alters the ecology of its new home.

 

The Argentine ant thrives in a warm climate with abundant water, and is often found on agricultural lands or near cities. But it also invades natural areas, said U. of I. entomology professor Andrew Suarez, principal investigator on the new study. The ant is highly social, and sometimes forms immense "super-colonies" made up of millions workers spread over vast territories. In previous research, Suarez identified a super-colony in California that stretched from San Diego to San Francisco.

 

In the new study, Suarez and colleagues followed an invasion wave of Argentine ants across Rice Canyon, in southern California.

 

The researchers tracked the invasion for eight years, collecting data on conditions before and during the invasion.

 

"Rather than comparing an invaded to a non-invaded community, which may be different for all sorts of other reasons, we try to follow an invasion front in real time to document what this invader is doing," Suarez said.

 

The researchers used a technique called stable isotope analysis to determine what the ants were eating. By calculating the ratio of heavy to light isotopes (molecular weights) of nitrogen in all members of an ecological community, scientists can determine if a particular organism is primarily a carnivore or herbivore.

 

What the researchers found surprised them. In the early stages of invasion the Argentine ants behaved much as they did in their own home ranges: They were carnivores, aggressively attacking and probably eating most of the other ants they encountered. But as they displaced the native species, they began foraging lower on the food chain.

 

Field studies showed that the ants were taking over an important food source: the honeydew excretions of aphids and scale insects that feed on plants.

 

"These are really important, often fixed resources, from which ants can get a huge amount of their carbohydrate fuel, the energy to fuel their worker force," Suarez said. "As the native ants are displaced, the Argentine ants start monopolizing these resources."

 

The impact on the natives was disastrous. Over a period of eight years, the number of native ant species in the study area went from 23 to two.

 

The findings point to a need for more long-term studies of native and non-native species, Suarez said, rather than the more common, short-term studies, which see only a fragment of the bigger puzzle.

 

"The way the invasive species are interacting with the environment might actually be changing over time," Suarez said.

 

Only by following an invasion over time can researchers begin to understand the dynamics that allow alien species to win out over the natives, he said.

 

Source: University of Illinois

[Drum]

This is a good post, altho I disagree with some descriptions in it. This Ant is described as agressive, This ant is agressive in the sense that it outcompetes all other sub-species for food. But it is not an agressive (violent) ant. In fact its personality is contained in its name, I believe, 'Humile'

 

Also this is not a novel species. Iridomyrmex Humilus, of which Linepithema humile, (I believe) is just the Argentine variety has been conquering the earth since the early 1900s, using exactly the same tactics.

 

There unique mutant adaptation lies in the ability, or defect, that as soon as they get too far from their 'home base', instead of returning the foraged food to home base, they establish a new storehouse ... This becomes their new 'home' from which they forage. The old homebase workers plunder this new storehouse as a source of food. The inhabitants of the new storehouse do not mind the plunder ... quite often jostling for position to get more food in while others are removing it.

 

I have performed many experiments with these ants, operating killing fields, where only a single ant is allowed to cross to pass on information.

 

I am a total amateur, but my 'results' from many years of experimentation can be trusted (I grow my own vegies in the city and have garden beds on my balcony ... inhabited by these ants)

 

1 .. Individual ants have no awareness ... They communicate by touch and sound (they make a noise that cannot be heard by our ears all the time ... absence of this sound alerts those nearby to danger). If you fail to reply with the 'masonic symbol' of identity, the ritual sound followed by touching feelers .. then you are food. Even by removing a single antenna from an ant, others will then consider him as food ... not an ant

 

Ergo: they are not aware ... A computer program could simulate all their standard responses to standard inputs. Ants can track where other ants have walked

 

2.. The colony has a 'group' intelligence that no individual ant is aware of. This intelligence, or part there of can be carried by any ant. Eg: In an experiment, repeated a few times, a ant (A) has found food ... he bumps into another ant (B), I kill A, B bumps into another ant ©, I kill B, and so on .... the last ant, who never saw the food and received his information 10th hand (the other 9 are dead) knows where the new food store is.

 

3... The genuis of their adaptation lies in the fact of many small, colonies. These colonies may be thought of as connected, even related. I don't think this is so, the ant of any colony does not object to any other ant removing food from his colony ... he is not Agressive .. in this way all colonys share ... one ant's colony is another ant's foraging site. But the colonies are not aware of each other.

 

..........for an invader to slaughter this single queen to cause the destruction of the colony. Iridomyrmex has remedied this condition to a remarkable degree. The queens of Iridomyrmex are tiny, soft bodied, and active, but little larger in stature than the workers. very many are permitted to coexist in a single colony. Queens of this type are easily and inexpensively reared in large numbers. ...........

 

Colonies of these ants bud, and divide, again and again, each new division taking a few queens with it, and therby rendering itself nearly impregnable against extermination. ....

 

Armed with these social weapons, Iridomyrmex humilus a few years ago undertook a campaign of expansion which has left almost no part of the tropical world which is inhabited by humans unknown to it. its original home seems to have been Argentina. It has become an adept at living within houses and ships ...... (1939)

 

So good post .... and heres to the laid-back ant ... perhaps we can all learn a lesson from him

 

cool bananas ... Drum :evil:

[Racoon]

Interesting reply, Drum..

Ants are indeed perhaps the most successful creatures on earth..

 

I haven't encountered these Argentinians before, so I can't say for sure, but it sounds like they ARE aggressive. Or they wouldn't be encroaching on foreign territory..

 

I wonder who would win in a battle of Army Ants vs. Argentinian ants ? :evil:

 

Maybe thats what Earth will boil down too if Humans keep it up. A world of competing ant super-colonies??

[Drum]

Interesting reply, Drum..

Ants are indeed perhaps the most successful creatures on earth..

 

I haven't encountered these Argentinians before, so I can't say for sure, but it sounds like they ARE aggressive. Or they wouldn't be encroaching on foreign territory.. I wonder who would win in a battle of Army Ants vs. Argentinian ants ? :evil:

 

They are agressive in their conquest of territory ... but I have never seen them physically attack another, or even one of their own, species. Unless the other ant is damaged or wounded ... in which case they consider it food ... if it puts up too much of a fight they desert and continue foraging.

 

Almost any other species of ant could defeat them as they are small, soft and easily killed.

 

Maybe thats what Earth will boil down too if Humans keep it up. A world of competing ant super-colonies??

 

Well Racoon ... in my observations ... and I know you will probably laugh ... but in some ways these colonies are very like a human. We are made up of individual cells, none of which are directly aware of any other ... yet combined we have intelligence.

 

The ants are the same if you consider each one as a cell. Only the colony has any awareness.

 

The difference, in this respect, between an ant-colony and a human is that there cells (ants) are not so closely bound together this gives them a less degree of intelligence but a greater degree of freedom.

 

Imagine if you could suddenly separate all your cells and let them glide under a door and re-assemble on the other side .... magic ... and great for foraging food. LOL

 

cool bananas ... Drum B)