Thursday, 27 September 2018

A study of ants provides information on the evolution of social insects

September 10, 2018, Universitaet Mainz
One of the great puzzles of evolutionary biology is what induced certain living creatures to abandon solitary existence in favor of living in collaborative societies, as seen in the case of ants and other social, colony-forming insects. A major characteristic of so-called eusocial species is the division of labor between queens that lay eggs and workers that take care of the brood and perform other tasks. But what is it that determines that a queen should lay eggs and that workers shouldn't reproduce? And how did this distinction come about during the course of evolution? Evolutionary biologist Dr. Romain Libbrecht has been considering these problems over the past years and in cooperation with researchers at Rockefeller University in New York City has found a completely unexpected answer: one single gene called insulin-like peptide 2 (ILP2), which is probably activated by better nutrition, stimulates the ovaries and triggers reproduction.
"It may seem almost inconceivable that just one single gene should make all the difference," Libbrecht pointed out. The researchers drew their conclusion from a comparison of 5,581 genes in seven ant species in four different subfamilies that differ from each other with regard to numerous characteristics. But in one thing are they all alike: there is always a greater expression of ILP2 in the brain of reproductive insects. Queens thus have higher levels than workers. A further finding indicates that this peptide is found only in the brain, where it is produced in a small cluster of just 12 to 15 cells.
Division of reproduction and brood care as the basis of social colony formation
It is postulated that the origins of social behavior in insects are to be found in wasp-like ancestors that alternated between reproduction and brood care phases. A female wasp would lay an egg and take care of the larva until it pupated. However, these two phases were separated and their associated duties assigned to different individuals, namely queens and workers, during the evolution of eusociality.

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