It is generally believed that the evolution of living things occurs over a long time scale of several thousand years or more in response to the environment in which they live. On the other hand, the environment changes significantly throughout the seasons, and for organisms with short generations such as insects, it is expected that the driving force (selective pressure) that drives evolution differs between seasons.

　To verify this, in this study we investigated whether the phenotypes (characteristics) of the yellow-banded Drosophila melanogaster, whose generation length is several weeks, change with the seasons. It is necessary to properly evaluate whether the differences in phenotype are due to evolution rather than due to the measured seasonal environmental conditions (temperature and humidity), so after wintering (mid-February to early March) The ``spring generation'' flies collected and the ``autumn generation'' flies collected after the summer (early October to early November) were reared and bred under a certain environment in the laboratory. Both the "spring generation" and the "autumn generation" are repeatedly crossed with genetically similar parents to establish inbred lines, and by simultaneously measuring the phenotypes of subcultured individuals using this, we are able to eliminate environmental factors. You can remove the influence and compare.

As a result of attempting to detect phenotypic differences resulting from evolution, we found significant changes in body size and high temperature tolerance between the ``spring generation'' and ``autumn generation.'' It has been found that the ``autumn generation'' has a larger body size and is more tolerant of high temperatures than the ``spring generation.'' In other words, it was shown that rapid evolution occurs in response to the seasons, with animals increasing their tolerance to high temperatures by experiencing summer and losing their tolerance to high temperatures by experiencing winter.

The results of this study are considered to be valuable evidence that suggests that organisms are evolving at an extremely high rate in response to seasonal environmental changes.

Paper information:[Scientific Reports] Rapid seasonal changes in phenotypes in a wild Drosophila population