Why did gold ants become mean? Genetic research reveals how queens spread horizontally

Research by biologists from MIT and Cambridge has revealed that when more than two copies of a gene are transferred from red ants to golden ant queens, a gene that allows the queen to spread horizontally at twice the speed of her neighbours is switched on.

Compared to neighbouring ants, alpha fives tend to stay in one place and reproduce in pairs, whereas a queen will just mash into anyone else. This confers several advantages: her queens spread twice as quickly as will healthy partners, and it also leads to larger reproduction rates. The researchers describe how this affects ant colonies in a paper published in Science on Thursday.

We initially shared the genetic variants with their mates but a second generation of pairs reared the queens and their offspring and we adapted. Dr Nick Simon

The mechanism that allows queens to quickly spread horizontally is the double t-transferase variant of apolipoprotein A, or APP. Elevated expression of the T-transferase variant in the queen gene, C-clincin, resulted in overloading the default gene production bottleneck. From 2000 to 2012, leading biologists throughout the continent established this novel South African behaviour was triggered by larger, aggressive females. This observation confirmed the primacy of larger female and deferred parenthood but it’s the amazing twist this discovery has made possible that makes the findings really shine.

The researchers turned up the volume on the female’s aggression by playing recordings of “chirping” sounds through a loudspeaker to pitqueens: females that are good at spreading horizontally become aggressive and subsequent queens respond by delivering more energy to their offspring and infecting the rest of the colony with offspring of the aggressive females.

Between 2000 and 2004, the MIT group successfully controlled the number of mates and subordinate females in an ant colony for the first time in an ant colony, demonstrating the richness of the habitable gene pool. Their work in charge of the genetics of small green ants in 2005 showed how queens change male t-transferase phenotype by splicing in other APSB variants to create a new gene that enhances lateral spread. That experiment provided the nucleostructure needed to direct the researchers to the code for the APSB T-transferase variant C-clincin.

Recently, they took their understanding a step further. First, the results were thought to depend on extracellular processes in the host cells; but the researchers have moved on to explain how the queens can spread horizontally. In a paper in Science published in 2015, they showed how after twice the gene doubling the heart rate of queens dropped 70% and they could not double the transit time, which lets the queens spread horizontally faster.

Next, the MIT-Cambridge group linked the effect of the double t-transferase variant of APSB to patterns of female aggression in thousands of female red ants. Like their little brothers, the queens in mating pairings reached dominant status by making more, thus assaulting the available mates. Females, on the other hand, came to dominance in pairs of mates by hitting smaller partners more aggressively and neutralising them with sexual charges.

In the new paper, lead author and Charles River College of Engineering PhD student Benjamin Martini showed that the second generation queens were able to jump into a more aggressive, altruistic and explosive mode that accelerates their lateral spread.

Source: University of Cambridge and MIT

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