Small but mighty: the evolutionary dynamics of W and Y sex chromosomes.
Although sex chromosomes have been the focus of a great deal of scientific scrutiny, most interest has centred on understanding the evolution and relative importance of X and Z chromosomes. By contrast, the sex-limited W and Y chromosomes have received far less attention, both because of their generally degenerate nature and the difficulty in studying non-recombining and often highly heterochromatic genomic regions. However, recent theory and empirical evidence suggest that the W and Y chromosomes play a far more important role in sex-specific fitness traits than would be expected based on their size alone, and this importance may explain the persistence of some Y and W chromosomes in the face of powerful degradative forces. In addition to their role in fertility and fecundity, the sex-limited nature of these genomic regions results in unique evolutionary forces acting on Y and W chromosomes, implicating them as potentially major contributors to sexual selection and speciation. Recent empirical studies have borne out these predictions and revealed that some W and Y chromosomes play a vital role in key sex-specific evolutionary processes.
Department of Zoology, Edward Grey Institute, University of Oxford, South Parks Road, Oxford, UK. Judith.Mank@zoo.ox.ac.uk
Judith E
JE
Mank
D000818:Animals; D001717:Birds; D019143:Evolution, Molecular; D005260:Female; D056084:Genetic Fitness; D056426:Genetic Loci; D049810:Genetic Speciation; D008297:Male; D008322:Mammals; D011156:Population Density; D011995:Recombination, Genetic; D012641:Selection, Genetic; D012723:Sex; D014998:Y Chromosome / Q000235:genetics* / Q000502:physiology