Published August 26, 2021 at 12.44
Domestic. Despite the fact that the male y-chromosome contains very few genes, it can dramatically change the body size of males and thus make the evolution of differences between the sexes possible. This is shown by a research group at Uppsala University after studying beetles.
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Females and males often differ in many ways in terms of morphology, physiology and behavior.
These differences between the sexes are called gender dimorphism and how such differences develop is a mystery because females and males share the same gene set. An evolutionary change in one sex should therefore bring about a corresponding change in the other. In this way, the evolution of gender differences should be stopped.
The new study, published in the journal Nature Ecology & amp; Evolution, shows that even small genetic differences between the sexes can enable the evolution of gender dimorphism in just a few generations.
– Our experiments show that the y-chromosome alone can change the sex difference in size by as much as 30 percent, says Philipp Kaufmann, doctoral student at the Department of Ecology and Genetics at Uppsala University, in a mailing.
He continues:
– It is remarkable that in these beetles, just like in humans, the y-chromosome contains only a handful of genes and constitutes only a very small part of the genome. Many people have thought that the y-chromosome only affects the most important reproductive process in males, sperm production. The results of our study suggest that the y chromosome may have a broader role than previously thought.
However, the evolution of gender dimorphism depends not only on where in the genome the genetic variation is, but also on how natural and sexual selection can affect it. With the help of lab evolution, the research group was able to show that gender dimorphism in body size could develop when there was a selection pressure on the size of males. But when the selection only acted on females, the shared part of the genome caused a correlated evolutionary response in males as well, which prevented the development of dimorphism.
– The most dramatic change in gender dimorphism between males and females, an increase of 50 percent in just ten generations took place when we directed the selection to become antagonistic and thus favored the opposite body size of the two sexes. This shows that under the right kind of selection, gender differences can obviously develop quickly. Maybe easier than we previously thought, says Elina Immonen, research assistant at the Department of Ecology and Genetics, Uppsala University, who led the study.