The origin of the apple fly

Apple flies have been of interest to scientists since the mid-19th century, as they are a good example of splintering, the beginning of a new species. Letters between Charles Darwin and Benjamin Walsh, who observed apple flies and blackflies in North America, began the rich history of this scientific question in evolutionary biology. When North American settlers brought apple trees into the area, what happened inside the hawthorn flies to force them to move to this new host plant in the last 300 years?

Following the 160-year research into the origins of the apple fly, a team of scientists from around the world have published their research in the Proceedings of the Royal Society B.. The researchers span three continents, from the National Center for Biological Sciences, University of Cross-disciplinary Health Sciences and Technology, University of Notre Dame, Free University of Berlin, and Max Planck Institute for Chemical Ecology. They have been studying the neurological processes that underlie important behavioral changes in the apple fly: choice of a new host plant and choice of companion. These behavioral changes contributed to a rapid transition from hawthorn flies to a race of apple-feeding flies.

Hawthorn flies and apple flies are special insects, they eat only on certain fruits, either kidney berries or ripe apples. They also breed on or near the fruit and lay their eggs there. The interesting thing about apple and hawthorn flies is that each generation presents with a specific preference for the scent of ripe fruit which they use to find their host and a strong influence on the aroma of other fruits. What is different from these two flies races?

Using records of electrical activity and imaging the brains of flies, the team identified that both apple and hawthorn flies use the same brain regions to process odors, but change the processing locations. . In other words, where apple flies process the main smell of apple (butyl hexanoate) in the same place in the brain where hawthorn flies process the main scent of hawthorn (3-methyl-1-butanol), and vice versa . Thus, the places for selection and movement for fruit scents remain as they are, while the scents processed there are reversed.

The scientists were able to find the specific point where this difference appears. It is at the first synapse in the olfactory system, called the antennal lobe. “What surprised me was to see olfactory processing be so clearly different between the host races of the apple and hawthorn plague. We knew that these flies have different fly behaviors and patterns between Now, from this work we know that their sensory neurophysiology is also different, “said Cheyenne Tait, the first author of the study.

It is possible that a simple shift in the processing of important sensory information could contribute significantly to the diverse species we see. “We are seeing the materialization of profitability. The originality of new species is one of the great questions that has broken the intellectual curiosity of mankind. Solving the question of profitability is of great scientific importance and continuous evolution. apple and hawthorn host races Rhagoletis is associated with life itself, or the origin of new life forms, “says Jeffrey L. Feder, an expert in evolutionary biology and one of the experts involved in the study.

Through the change in neurological processing of fruit odor, change at the scale of sex can be induced. Shannon Olsson explains her fascination with the flies, “What amazes me most is the simplicity of the version – these flies changed their minds alongside the species. contributing to the change in behavior that helps shift evolution to new species. “

This is not just a question of the past, or the evolutionary history of one species, “This discovery has an important impact on how animals such as insects can adapt their behavior to new environments, such as with invasive species, or responding to human – induced changes in climate or land use, “adds Shannon. Many biology subfields came together for this study to understand more about these two flies. There is more to be found in how scientists approach evolution from new perspectives and with exciting advances in technology that can be used to study these issues.

Presented by the National Center for Biological Sciences