China’s historical isolation influenced fruit flies

May 13. () –

Fruit flies (Drosophila melanogaster), which humans have inadvertently spread around the world, They arrived in China approximately 4,000 years ago.

It is the conclusion of a new population genomics study that contributes to our understanding of global migration, demography, gene flow and insect adaptations.

Researchers found that Chinese fruit fly populations have been genetically isolated, and that isolation reflects China’s ancient culture and its relatively closed society with limited trade with Asia and Europe for many centuries. This isolation also allowed the authors to see if similar evolutionary pressures resulted in similar genetic changes, a test of the repeatability of evolution.

“The surprising story of Drosophila melanogaster is that its genetic differences between populations reflect how humans spread, from an origin in Africa, followed by migration out of Africa, but it is much more recent,” he said. it’s a statement Andrew Clark, professor of Population Genetics at Cornell University, and first author of the study, published in Science Advances.

The authors combined their own results with those of previous studies and propose that D. melanogaster originated in southern Africa and migrated from northern Africa about 9,000 years ago. From there, flies spread to eastern Asia and China (about 2,800-4,400 years ago), to Europe (about 1,800 years ago), and, more recently, to North America (only about 150 years ago) and Australia (about 1,800 years ago). about 100 years ago).

Flies are a human commensal: an organism that benefits from an association with another organism from which it derives neither benefit nor harm. They thrive on rotten fruit in orchards and vineyards.

DISSEMINATION WITH TRADE

“Humans left Africa about 80,000 years ago, but agricultural fruit production began less than 10,000 years ago.“Clark said. “It’s really modern human trade that helped disperse flies around the world.”

In the study, the researchers sequenced the genomes of 292 strains of D. melanogaster from various environments in China and analyzed them together with previously published genomic sequences. They found that the strains from China represented a unique ancestry group, with notable differentiation between subpopulations within China. The article clarifies the extent and duration of isolation of Chinese populations, a result that has only been hinted at in previous studies.

The global population genomic data allowed the researchers to develop a computer model to estimate the times when D. melanogaster arrived on each continent and infer how genetic changes, which cluster in the genomes of closely related strains, They correspond to geographical movements.

D. melanogaster is a model organism widely used by researchers to study fundamental processes of development and genetic regulation, as well as the genetic basis of environmental adaptation. In the study, Clark, Lu and their colleagues identified genetic changes in response to insecticides.

“When humans apply insecticides, tremendous pressure is put on the population, and many insects develop resistance relatively quickly,” Clark said. These changes are usually quite simple genetically, Clark said, and involve only a few genes that have a large effect, unlike complex traits that can involve hundreds of genes.

The adaptations that occurred in the Chinese populations were independent of other geographic populations and occurred as unique mutations in the same genes found in other populations that have developed resistance to insecticides. “It’s a good example of a repeated natural test of evolution with basically the same result,” Clark said.