Male flies love lives

Evolution in real time revealed by manipulation of fly sexual selection

Drosophila flies sexual selection intensity can be experimentally manipulated in real time, to examine evolutionary processes. Dr. Snook discussed her recent findings on the ways in which Drosophila pseudoobscura respond to intensity of sexual selection.

Intensity of sexual selection was established by enforced monogamy for no selection (M), controlled promiscuity for natural levels of sexual selection (C) and elevated promiscuity for increased opportunities for variance in drosophila males (E) 1.

Pre-copulatory responses to intensity of sexual selection caused E males to court1 and mate2 more than C and M males, therefore gaining greater fitness2. Snook recently has explored competition between different treatments, E males mate more and M males spend more time courting3. But there was no effect of male and female sexual selection treatment on copulation duration3. Drosophila song, E males sing faster4; and the size and shape of their wings are also influenced5.
Post-copulatory factors include sperm competition and accessory gland proteins. Drosophila obscura group’s sperm are heteromorphic. They have two different morphs of sperm long fertile and short infertile sperm 6. When Snook et al.looked at ejaculate investment, the number and length of sperm lacked a response to any sexual selection treatments1. This could be due to insufficient genetic variation, for a response to occur. Snook suggested females may constrain sperm evolution via reproductive tract evolution.  Accessory gland proteins influence female egg laying and the size of accessory gland were significantly larger in E males1. Differences in sexual selection intensity Snook and colleagues have shown evolution in flies which is very impressive. Our understanding of flies’ responses to sexual selection shows its affects their evolution.


  1. Crudgington, H.S., Fellows, S., Badcock, N.S. & Snook, R.R. Evolution63, 926-938 (2009).
  2. Crudgington, H.S., Fellows, S. & Snook, R.R. Evol. Biol. 23, 440-446 (2010).
  3. Debelle, A., Ritchie, M.G. & Snook, R.R. Unpublished.
  4. Snook, R.R., Robertson, A., Crudgington, H.S. & Ritchie, M.G. Behav. Genet. 35,245-255 (2005).
  5. Gidaszewski, N., Moore, A., & Snook, R.R. Unpublished.
  6. Holman, L. & Snook, R.R. Curr. Biol. 18,292-296 (2009).