Table of Contents
International Journal of Evolutionary Biology
Volume 2012 (2012), Article ID 963976, 10 pages
http://dx.doi.org/10.1155/2012/963976
Research Article

Inter- and Intraspecific Variation in Drosophila Genes with Sex-Biased Expression

1Department of Biology II, University of Munich (LMU), 82152 Planegg-Martinsried, Germany
2Institute for Evolution and Biodiversity, University of Münster (WWU), 48149 Münster, Germany

Received 13 July 2011; Revised 6 October 2011; Accepted 6 October 2011

Academic Editor: Artyom Kopp

Copyright © 2012 Lena Müller et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Genes with sexually dimorphic expression (sex-biased genes) often evolve rapidly and are thought to make an important contribution to reproductive isolation between species. We examined the molecular evolution of sex-biased genes in Drosophila melanogaster and D. ananassae, which represent two independent lineages within the melanogaster group. We find that strong purifying selection limits protein sequence variation within species, but that a considerable fraction of divergence between species can be attributed to positive selection. In D. melanogaster, the proportion of adaptive substitutions between species is greatest for male-biased genes and is especially high for those on the X chromosome. In contrast, male-biased genes do not show unusually high variation within or between populations. A similar pattern is seen at the level of gene expression, where sex-biased genes show high expression divergence between species, but low divergence between populations. In D. ananassae, there is no increased rate of adaptation of male-biased genes, suggesting that the type or strength of selection acting on sex-biased genes differs between lineages.