Table of Contents
International Journal of Evolutionary Biology
Volume 2011, Article ID 485460, 11 pages
http://dx.doi.org/10.4061/2011/485460
Research Article

Male-Female Interactions and the Evolution of Postmating Prezygotic Reproductive Isolation among Species of the Virilis Subgroup

Department of Biology, University of Winnipeg, 515 Portage Avenue, Winnipeg, MB, Canada R3B 2E9

Received 25 October 2010; Accepted 3 February 2011

Academic Editor: Jeremy Marshall

Copyright © 2011 Nada Sagga and Alberto Civetta. 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

Reproductive isolation reduces breeding between species. Traditionally, prezygotic and postzygotic barriers to reproduction have been broadly studied, but in recent years, attention has been brought to the existence of barriers that act after copulation but before fertilization. Here, we show that when D. virilis females from different geographic locations mate with D. novamexicana males, egg laying is normal, but fertilization rates are severely reduced, despite normal rates of sperm transfer. This reduction in fertilization is probably due to lower retention of heterospecific sperm in female storage organs one-to-two days after copulation. An inspection of egg hatchability in crosses between females and males from other virilis subgroup species reveals that isolation due to poor egg hatchability likely evolved during the diversification of D. virilis/D. lummei from species of the novamexicana-americana clade. Interestingly, the number of eggs laid by D. virilis females in heterospecific crosses was not different from the numbers of eggs laid in conspecific crosses, suggesting that females exert some form of cryptic control over the heterospecific ejaculate and that future studies should focus on how female and female-sperm interactions contribute to the loss or active exclusion of heterospecific sperm from storage.