SEX-CHROMOSOME TURNOVERS INDUCED BY DELETERIOUS MUTATION LOAD
Article first published online: 11 OCT 2012
© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Volume 67, Issue 3, pages 635–645, March 2013
How to Cite
Blaser, O., Grossen, C., Neuenschwander, S. and Perrin, N. (2013), SEX-CHROMOSOME TURNOVERS INDUCED BY DELETERIOUS MUTATION LOAD. Evolution, 67: 635–645. doi: 10.1111/j.1558-5646.2012.01810.x
- Issue published online: 5 MAR 2013
- Article first published online: 11 OCT 2012
- Accepted manuscript online: 20 SEP 2012 01:03PM EST
- Received February 6, 2012 Accepted September 3, 2012 Data Archived: Dryad: doi:10.5061/dryad.pk14p
- Dosage compensation;
- sex-antagonistic genes;
- sex-chromosome decay;
- sex determination
In sharp contrast with mammals and birds, many cold-blooded vertebrates present homomorphic sex chromosomes. Empirical evidence supports a role for frequent turnovers, which replace nonrecombining sex chromosomes before they have time to decay. Three main mechanisms have been proposed for such turnovers, relying either on neutral processes, sex-ratio selection, or intrinsic benefits of the new sex-determining genes (due, e.g., to linkage with sexually antagonistic mutations). Here, we suggest an additional mechanism, arising from the load of deleterious mutations that accumulate on nonrecombining sex chromosomes. In the absence of dosage compensation, this load should progressively lower survival rate in the heterogametic sex. Turnovers should occur when this cost outweighs the benefits gained from any sexually antagonistic genes carried by the nonrecombining sex chromosome. We use individual-based simulations of a Muller's ratchet process to test this prediction, and investigate how the relevant parameters (effective population size, strength and dominance of deleterious mutations, size of nonrecombining segment, and strength of sexually antagonistic selection) are expected to affect the rate of turnovers.