New study sheds light on how X and Y chromosomes interact

The results provide new clues on how species are formed, and suggest it could be harmful to bring together individuals from different populations that have been separated for a long time. The reason is that the offspring have lower survival rates.

"This is something worth keeping in mind in conservation biology, where you want to see a population grow," says Jessica Abbott, researcher in evolutionary ecology at Lund University.

It is previously known that hybrids between different species often do better if they are female (two X chromosomes) rather than male (X and Y chromosome).

In the study, the researchers crossed fruit flies from five different populations from different continents in order to combine X and Y chromosomes with different origins. They then followed and studied the subsequent generations.

The results show that males with X and Y chromosomes that don't match had higher reproductive success than males with matching X and Y chromosomes. However, the higher male fertility was paired with lower survival rates among their offspring.

"We were expecting the opposite, that males with different origin X and Y chromosomes would have lower reproductive success, so that was surprising," says Jessica Abbott.