Saturday, August 18, 2012

Assessing Direct and Indirect Costs

Orteiza, N., Linder, J., & Rice, W. 2005. Sexy sons from re-mating do not recoup the direct costs of harmful male interactions in the Drosophila melanogaster laboratory model system. Journal of Evolutionary Biology, 18(5), 1315-1323.

This article explores how female interactions with males can reduce lifetime survival and fecundity, and assesses any indirect benefits as a result. Virgin females were introduced into two conditions simulating constant male exposure and minimal male interaction. Wild-type males and virgin females are housed and allowed to mate, and then half the females are given the chance to re-mate again with brown eyed males. To determine any direct costs to females by re-mating and constant male exposure females were housed with brown-eyed females and would compete for limited yeast. The costs would then be calculated by recording the eye colour and number offspring each female produced. To assess any indirect benefits virgin females were allowed to mate once with a red-eyed male, and then given the chance to re-mate with a brown-eyed male. The male offspring were then separated according to whether their father was an initially mated or re-mated male and cultured to test for paternity. The study found that the grand-offspring of the re-mated male had slightly lower fecundity than the initially mated male and did not make up for the direct costs involved in re-mating caused by increased male exposure. It is estimated that about 10% of a female’s fecundity is lost through re-mating while about 3% is gained through indirect benefits.

Monday, August 13, 2012

Sex Ratio in Drosophila melanogaster Populations Effect Male Mating Success

Pavkovic-Lucic, S., Kekic, V., & Cvoro, A. 2009. Larger male mating advantage depends on the sex ratio in Drosophila melanogaster. Ethology Ecology & Evolution, 21(2), 155-160.

In this study the mating success of large and small males was examined under specific sex ratios. The mating status of females and males were held constant. Larger males were more successful than smaller males in conditions where the sex ratio was equal, and when there were more males present than females. When more females were present in the population there was no significant difference in mating success of large and small males. In all cases larger males mated earlier, while there was no significant size difference of mated females across the conditions. This is most likely due to the high tracking speeds and increased courtship of larger males. Larger males may have greater mating success than smaller males in male dominated sex ratios because of increased male-male competition. These findings support male-male competition as being an important factor in determining the mating success of larger males rather than a female preference for larger males.

Friday, August 10, 2012

Effects of Male Size on Mating Success and Female Preference in Drosophila melanogaster

Partridge, L., Ewing, A., Chandler, A. 1987. Male Size and Mating Success in Drosophila melanogaster: The Roles of Male and Female Behavior. Animal Behaviour, 35, 555-562. 

In this article the effects of male size in relation to courtship behavior was examined in a non-competitive environment to determine what factors lead to higher courting success in larger males. Male tracking speeds, song frequency and amplitude, as well as frequency of decamping by females was examined. Larger males exhibited louder and more frequent courtship songs as well as faster tracking speeds, while female decamping did not differ significantly among large and small males. This suggests that mating success by larger males is not due to female preference but rather a result of male-male competition. Although the frequency of decamping by the females did not differ, female preference for louder songs and their increased movement as a result of faster tracking speeds by larger males is an important factor in determining female preference for larger males and increased mating success among larger males in a non-competitive environment.

Wednesday, August 1, 2012

Food Cook!

Gradate Students Hannah Tennant and Adam Lounsbury mixing up a delicious batch of Drosophila banana media (yum!)