Many separate-sexed organisms have sex chromosomes controlling sex determination. Nachman MW, Payseur BA Recombination rate variation and speciation: theoretical predictions and empirical results from rabbits and mice. No amicable divorce? Using the Japan Sea species of threespine stickleback Gasterosteus aculeatuswhich has a neo-sex chromosome derived from a Y-autosome fusion, we found that incipient neo-X and neo-Y chromosomes have started to diverge in both coding and non-coding regions and to accumulate genes with sex-biased expression.
Next, we investigated whether neo-sex chromosomes contribute more to sex differences and species differences in mRNA expression levels than autosomes.
Sex chromosomes are generally considered to play special roles in phenotypic evolution and speciation. A second observation is that although many of the processes involved in sex chromosome differentiation are similar to those discussed in the speciation literature inversions, mutation accumulation, chromosomal rearrangements, etc.
Ellegren H. Biol J Linn Soc — Page DC.
View Article Google Scholar. When all of the five Pacific Ocean females had a homozygous variant and all of the five Japan Sea females had a homozygous variant different from that of the Pacific Ocean females and all of the five Japan Sea males had heterozygous variant at that locus e.
Though some organisms have lost the Y chromosome completely e. Top left corner: an autosome pair in a hermaphrodite gains a sex-determining factor that evolves to become a highly heteromorphic pair of sex chromosomes, via cessation of recombination, degeneration a and evolution of dosage compensation b.