X marks a new species

摘要

The discovery of a newly formed sex-chromosome system in a Japanese population of threespine stickleback - but not in a closely related species sharing the same habitat -provides evidence that sex-chromosome changes may have a greater role in causing reproductive isolation and speciation than was thought. Genetic mapping shows that the newly evolved X chromosome contains genes for male courtship behaviour, whereas the ancestral X chromosome contains genes for both behavioural isolation and hybrid male sterility. These traits contribute to an effective reproductive barrier between this species and the ancestral form found in the Pacific Ocean.