How do genes on sex chromosomes evolve in Timema?
In our new paper, we identify and examine patterns of sequence evolution and gene expression on the X chromosome across five Timema species.
Overall we find consistent evidence for relaxed selection on the X and complete dosage compensation in somatic tissues but not the reproductive tracts.
Interestingly, we also find that genetic diversity is much lower on the X than expected (X to autosomes ratio of 0.19 to 0.48, much lower than the expectation of 0.75), which may be due to a combination of a lower effective recombination rate on the X and population bottlenecks.
Finally, we find that dosage compensation in Timema seems to be due to the upregulation of the X chromosome in males. This mechanism is also common to all other XX/XY or XX/X0 insect systems yet studied, suggesting that this mechanism may be universal for insect species with heterogametic males.
