Stick insects retain gene-balancing after a million years without sex

Dr Darren Parker, a lecturer in evolutionary biology, explained that parthenogenesis, reproduction without the need for male fertilisation, had occurred naturally in some animal species.

As males and females have a different number of X chromosomes – males have one (XY), and females have two (XX) – “gene expression needs to be balanced equally” between the sexes.

Species had evolved mechanisms known as dosage compensation “to do just this”, he said.

But what happens if these mechanisms for equally sharing male and female genes are no longer needed?

“That’s the question we set out to answer,” said Parker.

“This is the precise situation found in asexually reproducing stick insects.

“Because the females reproduce without fertilisation from males, there is no need to equalise gene expression.

“By investigating gene expression in rare males, our study found that rather than decaying away as we expected, dosage compensation mechanisms remained fully functional despite not being needed for over a million years.”

His report has been published in scientific journal the Proceedings of the National Academy of Sciences (PNAS).