红火蚁体内存在一种“群居型”染色体

Researchers have discovered a social chromosome¹ in the highly invasive fire ant that helps to explain why some colonies allow for more than one queen ant, and could offer new solutions for dealing² with this pest. The red fire ants live in two different types of colonies: some colonies strictly³ have a single queen while other colonies contain hundreds of queens.

 

Publishing in the journal Nature on January 16, scientists have discovered that this difference in social organisation⁴ is determined⁵ by a chromosome that carries one of two variants⁷ of a 'supergene' containing more than 600 genes⁸.

 

The two variants, B and b, differ in structure but have evolved similarly to the X and Y chromosomes⁹ that determine the sex of humans. If the worker fire ants in a colony carry exclusively the B variant⁶, they will accept a single BB queen, but a colony that includes worker fire ants with the b variant will accept multiple Bb queens. The scientists analysed the genomes of more than 500 red fire ants to understand this phenomenon.

 

"This was a very surprising discovery -- similar differences in chromosomal¹⁰ structure are linked to wing patterns in butterflies and to cancer in humans but this is the first supergene ever identified that determines social behaviour," explains co-author Dr Yannick Wurm, from Queen Mary's School of Biological and Chemical Sciences.

 

"We now understand that chromosomal variants determine social form in the fire ant and it's possible that special chromosomes also determine fundamental traits such as behaviour in other species."

 

During the reproductive season, young winged queens from both types of colonies emerge for their mating flights and are fertilised by males. Young queens destined¹¹ to establish their own single-queen colonies disperse¹²（分散，传播） far and wide. This social form is highly successful at invading new territories. The other young queens join existing multiple-queen colonies close to their maternal¹³ colony. The multiple queens cooperating in such colonies are able to produce more workers than are found in a single-queen colony. This makes multiple queen colonies the more successful social form in busy environments.

 

The red fire ant is infamous¹⁴（声名狼藉的） for its painful sting in South America where it is a native species, and in many other parts of the world where its aggressiveness and high population density¹⁵ have made it an invasive pest. It was accidentally introduced to the Southern USA in the 1930s and has since spread to many warm parts of the world including China and Australia. Efforts at controlling the spread of this species have largely been unsuccessful, as indicated by its Latin name, Solenopsis invicta, meaning "the invincible¹⁶（无敌的）."

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