Washington, Jan 9 (IANS) The fungus-gardening ant is the only species of its kind to have dispensed with sex or males, says a new study.
Most social insects, wasps, ants and bees are used to life without males. Their colonies are well run by swarms of sterile sisters lorded over by an egg-laying queen.

But, eventually, all social insect species have the ability to produce a crop of males who go forth to fertilise new queens and propagate their species.

Queens of the ant Mycocepurus smithii reproduce without fertilisation and males appear to be completely absent, says Christian Rabeling, Ulrich Mueller and their Brazilian colleagues.

“Animals that are completely asexual are relatively rare, which makes this a very interesting ant,” says Rabeling, an ecology, evolution and behaviour graduate student at University of Texas at Austin (UTA).

“Asexual species don’t mix their genes through recombination, so you expect harmful mutations to accumulate over time and for the species to go extinct more quickly than others. They don’t generally persist for very long over evolutionary time,” he adds.

Previous studies of the ants from Puerto Rico and Panama have pointed towards the ants being completely asexual.

One in particular, by Mueller and former graduate student Anna Himler (now at Arizona State University), showed that the ants reproduced in the lab without males and that no amount of stress induced the production of males, said an UTA release.

Scientists believed that specimens of male ants previously collected in Brazil in the 1960s could be males of M. smithii. If males of the species existed, it would suggest that at least from time to time the ants reproduce sexually.

Scientists estimate the ants could have first evolved within the last one to two million years, a very young species given that the fungus-farming ants evolved 50 million years ago.

These findings were published in PLoS ONE this week.