The effects of sex-biased gene expression and X-linkage on rates of adaptive protein sequence evolution in Drosophila.
A faster rate of adaptive evolution of X-linked genes compared with autosomal genes may be caused by the fixation of new recessive or partially recessive advantageous mutations (the Faster-X effect). This effect is expected to be largest for mutations that affect only male fitness and absent for mutations that affect only female fitness. We tested these predictions in Drosophila melanogaster by using genes with different levels of sex-biased expression and by estimating the extent of adaptive evolution of non-synonymous mutations from polymorphism and divergence data. We detected both a Faster-X effect and an effect of male-biased gene expression. There was no evidence for a strong association between the two effects--modest levels of male-biased gene expression increased the rate of adaptive evolution on both the autosomes and the X chromosome, but a Faster-X effect occurred for both unbiased genes and female-biased genes. The rate of genetic recombination did not influence the magnitude of the Faster-X effect, ruling out the possibility that it reflects less Hill-Robertson interference for X-linked genes.
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK.
Victoria
V
Ávila
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK.
José L
JL
Campos
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK brian.charlesworth@ed.ac.uk.
Brian
B
Charlesworth
D000220:Adaptation, Biological; D000818:Animals; D029721:Drosophila Proteins / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D015870:Gene Expression; D017344:Genes, Insect; D050172:Genes, X-Linked; D008297:Male; D011110:Polymorphism, Genetic; D012737:Sex Factors
D029721:Drosophila Proteins
Drosophila; Faster-X effect; recombination; sex-biased gene expression; sexual selection