Project description.

Project in collaboration with Jesper Bechsgaard and Mads Fristrup Schou.

Faster-X, the greater evolutionary rate of the X-chromosome as compared to the autosomes, can occur when one sex is hemizygous for the X-chromosome. 
This can be adaptive if caused by fixation of recessive advantageous mutations exposed to selection, or non-adaptive if caused by the reduced efficacy of purifying selection on deleterious mutations due to the low Ne of the X-chromosomes. But this distinction is very rarely made. 
The relative importance of non-adaptive and adaptive faster-X is predicted to depend on Ne and the effective sex ratio. 
Faster-X may therefore impact species very differently, and this is likely to be most extreme in species of varying levels of sociality where Ne differences are large. 

We compare sub-social and social spider species in the genus Stegodyphus, where faster-X has been shown in previous work.  
We use 3 pairs consisting of a social and a sub-social sister-species, and whole-genome sequencing to ask:  
    - Is faster X evolution caused by adaptation of beneficial recessive variants on the X chromosomes or by drift due to lower effective population size of the X chromosomes? 
    - Does the proportion of substitutions caused by selection and drift vary between social and sub-social species? 

https://aarhusuniversitet-my.sharepoint.com/:w:/r/personal/au473112_uni_au_dk/Documents/Faster%20X/Faster_X_Extended_Outline.docx?d=w57fbd1fc384e473a83e14b7cf71e8ad0&csf=1&web=1&e=ZoN0F9