Table of Contents
International Journal of Evolutionary Biology
Volume 2011 (2011), Article ID 214280, 10 pages
http://dx.doi.org/10.4061/2011/214280
Research Article

Associations between Variation in X Chromosome Male Reproductive Genes and Sperm Competitive Ability in Drosophila melanogaster

1Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853-2801, USA
2Department of Developmental Biology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065-6094, USA

Received 11 January 2011; Accepted 7 March 2011

Academic Editor: Jeremy Marshall

Copyright © 2011 Leah Greenspan and Andrew G. Clark. 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

Variation in reproductive success has long been thought to be mediated in part by genes encoding seminal proteins. Here we explore the effect on male reproductive phenotypes of X-linked polymorphisms, a chromosome that is depauperate in genes encoding seminal proteins. Using 57 X chromosome substitution lines, sperm competition was tested both when the males from the wild-extracted line were the first to mate (“defense” crosses), followed by a tester male, and when extracted-line males were the second to mate, after a tester male (“offfense” crosses). We scored the proportion of progeny sired by each male, the fecundity, the remating rate and refractoriness to remating, and tested the significance of variation among lines. Eleven candidate genes were chosen based on previous studies, and portions of these genes were sequenced in all 57 lines. A total of 131 polymorphisms were tested for associations with the reproductive phenotypes using linear models. Nine polymorphisms in 4 genes were found to show significant associations (at a 5% FDR). Overall, it appears that the X chromosomes harbor abundant variation in sperm competition, especially considering the paucity of seminal protein genes. This suggests that much of the male reproductive variation lies outside of genes that encode seminal proteins.