Fire Ants Spurn Sex to Protect Genes, Study Says

Stefan Lovgren
for National Geographic News
June 29, 2005

Queens and males of an invasive ant species known as the little fire ant reproduce by cloning themselves, thereby keeping the gene pools of females and males separate, a new study reveals. Only sterile worker ants of the species are produced by sexual reproduction.

Clonal or asexual reproduction is not unique to little fire ants. Some lizard species, for example, produce female offspring clonally from adult females.

"What is unique about this ant is that not only are females produced clonally by females, but males are also produced clonally by males," said David Queller, an evolutionary biologist at Rice University in Houston, Texas, who was not invovled with the study.

The findings are reported in tomorrow's issue of the journal Nature.

Sexual Conflict

Sexual reproduction is the predominant force in the propagation of animals and many plants. However, it can lead to conflicts between the sexes. Characteristics that enhance the reproductive success of one sex can reduce the success of the other: Asexual females, for example, do not have to produce males to ensure future reproduction.

In most ants, females are typically produced by sexual reproduction, while males develop from unfertilized eggs.

But the small fire ant (Wasmannia auropunctata), which is considered an invasive pest in tropical habitats, is different, scientists found.

They have determined that queens and males each produce offspring with genes identical to their own, except when reproducing the sterile worker ants.

"In the evolutionary battle of opposing sexes, queens transfer all their genes to the reproductive females, and males thwart queens by eliminating the female genome during sexual brood development," said Denis Fournier at the University Libre de Bruxelles (Brussels) in Belgium. Fournier was the lead researcher of the study.


The ant's unusual reproductive strategy probably arose because queens sought to protect their own genes by clonal reproduction, using sexual reproduction only to produce workers.

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