A role for a neo-sex chromosome in stickleback speciation.

Publication Type:

Journal Article


Nature, Volume 461, Issue 7267, p.1079-83 (2009)


2009, Animals, Body Size, Center-Authored Paper, Comparative Medicine Core Facility, Crosses, Genetic, Female, Genetic Speciation, Genomics Core Facility, Human Biology Division, Hybridization, Genetic, Infertility, Male, Japan, Male, Mating Preference, Animal, Oceans and Seas, Pacific Ocean, Polymorphism, Single Nucleotide, Quantitative Trait Loci, Reproduction, Sex Characteristics, Sex Chromosomes, Shared Resources, Smegmamorpha, Social Isolation, Y Chromosome


Sexual antagonism, or conflict between the sexes, has been proposed as a driving force in both sex-chromosome turnover and speciation. Although closely related species often have different sex-chromosome systems, it is unknown whether sex-chromosome turnover contributes to the evolution of reproductive isolation between species. Here we show that a newly evolved sex chromosome contains genes that contribute to speciation in threespine stickleback fish (Gasterosteus aculeatus). We first identified a neo-sex chromosome system found only in one member of a sympatric species pair in Japan. We then performed genetic linkage mapping of male-specific traits important for reproductive isolation between the Japanese species pair. The neo-X chromosome contains loci for male courtship display traits that contribute to behavioural isolation, whereas the ancestral X chromosome contains loci for both behavioural isolation and hybrid male sterility. Our work not only provides strong evidence for a large X-effect on reproductive isolation in a vertebrate system, but also provides direct evidence that a young neo-X chromosome contributes to reproductive isolation between closely related species. Our data indicate that sex-chromosome turnover might have a greater role in speciation than was previously appreciated.