26.02.2020: Although men and women have almost the identical set of genes, they differ in many traits. The same is true for fruit flies. In a recently published study in eLife, a team of researchers from Vetmeduni Vienna has now shown that these differences can be important for adaptations to new environmental conditions. Using experimental evolution in the laboratory, Drosophila males and females developed different adaptations upon exposure to a high temperature. These adaptations are being driven by altered sex-biased gene regulation from standing genetic variation, rather than by new mutations. This mechanism can facilitate rapid evolutionary responses – an insight that is also of enormous relevance for humans.

The differences between the sexes have been a topic of great general interest not only since the publication of John Gray’s bestseller Men Are from Mars, Women Are from Venus. Evolutionary biologists have investigated this matter as well, coming to the conclusion that sexual dimorphism evolved through sex-specific adaptation. “Females typically evolve to produce and raise as many offspring as possible, while males must increase their mating frequency and success of fertilization,” says the study’s first author, Sheng-Kai Hsu. The amazing thing is that the needs of each of the sexes are sometimes diametrically opposed. This raises the question of how sex-specific adaptation can occur despite the fact that males and females have almost the same genome. Evolutionary biologists generally assume that the resolution of these sexual conflicts typically takes a very long time and that in the meantime a compromise between the needs of the sexes must be found.

Rapid evolutionary adaptation to higher temperatures

A team led by Christian Schlötterer, head of the Institute of Population Genetics at Vetmeduni Vienna, investigated the effects of environmental change on adaptive processes using Drosophila fruit flies. “We initially expected that environmental change would have the same impact on both sexes. So we were extremely surprised to see males and females evolve in opposite directions after just a hundred generations,” says Schlötterer.

Sex-specific genetic variation as a driver for rapid evolution

Supported by computer simulations, the researchers propose that altered sex-biased gene regulation from standing genetic variation, rather than new mutations, is the driver of rapid sex-specific adaptation. This conclusion is evidenced by the broad range of phenotypes evolving in different directions in males and females. The findings allowed the researchers to identify for the first time a mechanism of evolution that enables significantly faster adaptation to changing environmental conditions compared to gene mutations.

Evidence for the importance of gender-specific medicine

The results of the study underline the importance of experimental evolution. But the knowledge gained from basic research can also be of enormous relevance for practical applications and for new therapies in human medicine, says Christian Schlötterer: “Our discovery of environmentally driven divergent functional requirements of males and females has important implications – possibly even for gender-aware medical treatments. We anticipate that our results will have profound influence on biomedical research and medical treatments which need to account for the overwhelming differences of the two sexes, in particular with respect to new environmental stressors, reaching from diet to climatic conditions.”

The article “Rapid sex-specific adaptation to high temperature in Drosophila” by Sheng-Kai Hsu, Ana Marija Jakšić, Viola Nolte, Manolis Lirakis, Robert Kofler, Neda Barghi, Elisabetta Versace and Christian Schlötterer was published in eLife.