Fire Ants Start a Sexual Revolution

29 June 2005 (All day)

Selfish genes. Fire ant queens and males fight the battle to propagate their genes by reproducing clonally.

Fire ants have just added a new twist to the battle of the sexes. New research shows that, in one species, males and females clone themselves, creating entirely separate male and female gene pools.

Many social insects utilize different breeding strategies to produce males and females. Female ants, for example, hatch from fertilized eggs, so, like us, they get genes from both mom and dad. But male ants arise from unfertilized eggs, meaning they only get one set of genes--their mother's. Still, males aren't clones of their mothers because the mothers only contribute half of their own genetic material to their sons. Mom's genes came from grandma and grandpa, and the males can get various combinations of either set.

But not all ants reproduce this way, according to the new study. While investigating Wasmannia auropunctata, or "little fire ant," colonies in French Guiana and New Caledonia, a research team led by evolutionary ecologist Denis Fournier of the Université Libre de Bruxelles, Belgium, and population geneticist Arnaud Estoup of the National Agricultural Research Institute in Montferrier, France, discovered an unusual genetic pattern: The males and females were cloning themselves.

Genetic testing indicated that, contrary to other ants, queen W. auropunctatas arise from unfertilized eggs. As a result, they get both sets of genes from their mom and are thus exact copies of their mothers. Such a strategy could mean males have no chance to pass on their genes to future generations. But dads fight back. When they mate with queens, they somehow eliminate the maternal genetic contribution in the fertilized eggs that give rise to W. auropunctata males. Because the males are getting their only set of genes from their fathers, they, like the queens, are clones of their parent.

The clonality seen in queens and males results in a unique system where genes are passed down only to individuals of the same sex, keeping male and female gene pools separate, the team reports 29 June in Nature.

The results are "very exciting," says population geneticist J. Spencer Johnston of Texas A&M University in College Station. "Now you have an extreme example of sexual antagonism, where the male has taken it to a new level, essentially parasitizing the female to make his own offspring ... that's quite unique," he says. "In a sense, this is the closest we'll ever get to an all-male species," he adds.

Related sites
The study
Denis Fournier's lab
Information on the little fire ant

Posted In: