Ants give up sexuality to maintain social harmony

November 20th, 2008 - 3:34 pm ICT by IANS  

Toronto, Nov 20 (IANS) Highly specialised worker ants represent the pinnacle of social organisation in the insect world. As in any society, however, ant colonies are filled with internal strife and conflict. So what binds them together? More than 150 years ago, Charles Darwin had an idea and now he’s been proven right.

Evolutionary biologists at McGill University have discovered molecular signals that can maintain social harmony in ants by desexualising them.

Ehab Abouheif, of McGill’s department of biology and post-doctoral researcher Abderrahman Khila, have discovered how evolution has tinkered with the genes of colonising insects like ants to decide who gets to reproduce.

“We’ve discovered a really elegant developmental mechanism, which we call ‘reproductive constraint’, that challenges the classic paradigm that behaviour, such as policing, is the only way to enforce harmony and squash selfish behaviour in ant societies,” said Abouheif.

Reproductive constraint comes into play in these ant societies when evolutionary forces begin to work in a group context rather than on individuals, the researchers said, according to a McGill release.

The process can be seen in the differences between advanced ant species and their more primitive cousins.

Ants - organised in colonies around one or many queens surrounded by their specialised female workers - are classic examples of what are called eusocial organisms.

“More primitive, or ancestral, ants tend to have smaller colony sizes and have much higher levels of conflict over reproduction than the more advanced species,” Abouheif explained. “That’s because the workers have a much higher reproductive capacity and there is conflict with the queen to produce offspring.”

To their surprise, Khila and Abouheif discovered that “evolution has tinkered with the molecular signals that are used by the egg to determine what’s going to be the head and what’s going to be the tail, to stop the worker ants from producing viable offspring,” Abouheif explained.

The existence of sterile castes of ants tormented Charles Darwin as he was formulating his Theory of Natural Selection, and he described them as the “one special difficulty, which at first appeared to me insuperable, and actually fatal to my theory.”

The study appeared in Tuesday issue of the Proceedings of the National Academy of Sciences.

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