Data from: Long-term experimental hybridisation results in a heterologous transition and the evolution of a new sex chromosome in swordtail fish

The remarkable diversity of sex determination mechanisms known in fish may
be fuelled by exceptionally high rates of sex chromosome turnovers or
transitions. However, the evolutionary causes and genomic mechanisms
underlying this variation and instability are yet to be understood. Here
we report on an over 30-year evolutionary experiment in which we tested
the genomic consequences of hybridisation and selection between two
Xiphophorus fish species with different sex chromosome systems. We find
that introgression and imposing selection for pigmentation phenotypes
results in the retention of an unexpectedly large maternally derived
genomic region. During the hybridisation process, the sex-determining
region of the X chromosome from one parental species was translocated to
an autosome in the hybrids leading to the evolution of a new sex
chromosome. Our results highlight the complexity of factors contributing
to patterns observed in hybrid genomes, and we experimentally demonstrate
that hybridisation can catalyze rapid evolution of a new sex chromosome.