A multispecies approach for comparing sequence evolution of X-linked and autosomal sites in Drosophila.
Population genetics models show that, under certain conditions, the X chromosome is expected to be under more efficient selection than the autosomes. This could lead to 'faster-X evolution', if a large proportion of mutations are fixed by positive selection, as suggested by recent studies in Drosophila. We used a multispecies approach to test this: Muller's element D, an autosomal arm, is fused to the ancestral X chromosome in Drosophila pseudoobscura and its sister species, Drosophila affinis. We tested whether the same set of genes had higher rates of non-synonymous evolution when they were X-linked (in the D. pseudoobscura/D. affinis comparison) than when they were autosomal (in Drosophila melanogaster/Drosophila yakuba). Although not significant, our results suggest this may be the case, but only for genes under particularly strong positive selection/weak purifying selection. They also suggest that genes that have become X-linked have higher levels of codon bias and slower synonymous site evolution, consistent with more effective selection on codon usage at X-linked sites.
Vicoso
Beatriz
B
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK. b.vicoso@ed.ac.uk
Haddrill
Penelope R
PR
Charlesworth
Brian
B
D000818:Animals; D004330:Drosophila / Q000145:classification* / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D017344:Genes, Insect / Q000235:genetics*; D050172:Genes, X-Linked / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D014960:X Chromosome / Q000235:genetics
D029721:Drosophila Proteins