Scientists find that a new fire ant colony structure evolved in one species before spreading to others
Scientists from Queen Mary University of London have discovered that a new form of ant society is spreading across species. They found that after the new social form evolved in one species, a “social supergene” carrying the set of instructions for the new social form spread to other species. This propagation occurred by hybridization, that is to say by crossing between ants of different species. This unlikely event provides an alternative way of life, making the ants more successful than if they had only the original social form.
Red fire ants originally only had colonies with a single queen. The team previously discovered that around a million years ago, a new social form evolved where colonies could have dozens of queens. A particular version of a large section of chromosome, called the “social supergene”, includes the genetic information needed for workers to accept more than one queen. The new research, published today in Nature Communicationanalyzed the entire genomes or instruction sets of 365 male fire ants to examine the evolution of the social supergene and found that the same version of this chromosome is present in several species of fire ants.
The transfer of large amounts of genetic information between species is rare due to genetic incompatibilities. However, in this case, the advantages of having multiple queens outweighed the incompatibilities, and the genetic material repeatedly spread to other species from the source species in which this new social form has evolved. The multi-queen social form has advantages in several situations. For example, a colony with multiple queens has more workers and can therefore outcompete a colony with a single queen. Also, if there is a flood, a colony with multiple queens is less likely to become queenless.
Dr Yannick Wurm, Reader in Evolutionary Genomics and Bioinformatics at Queen Mary University of London and Fellow of the Alan Turing Institute, said: “This research reveals how evolutionary innovations can spread across species. It also shows how evolution works at the level of DNA and chromosomes.
“It was incredibly surprising to discover that other species could acquire a new form of social organization through hybridization. The supergene region that creates multi-queen colonies is a large piece of chromosome that contains hundreds of genes. The many Parts of a genome evolve to work together in fine-tuned ways, so suddenly having a mixture of different versions of many genes from another species is complicated and quite rare.
“Instead of running extra queens as they would in a single-queen colony, the new version of the supergene leads the workers to accept multiple queens. After thoroughly studying the history of the supergene and the new social form, we then want to identify which genes, or certain parts of the supergene region, drive these behavioral changes.This will also help fill more gaps in our understanding of evolutionary processes.
Rodrigo Pracana, one of the study’s lead authors, also at Queen Mary University of London, added: “Our study shows how detailed analysis of large numbers of wild animals can provide surprising new insights. on how evolution works.
The Queen Mary team was previously among the first in the world to apply large-scale DNA sequencing approaches to wild insects, which allowed them to discover one of the first well-known supergenes.
Red fire ants are native to South America and infamous for their painful sting. One of these species is known from many other parts of the world, where its aggressiveness and high population density have made it an invasive pest. Efforts to control the spread of this species have been largely unsuccessful, as its Latin name suggests, Solenopsis invictameaning “the invincible”.
The research was supported by the Leibniz Institute for the Analysis of Changes in Biodiversity, with the assistance of Dr Eckart Stolle as part of the Queen Mary team before continuing this work at the Leibniz Institute.
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