Tuesday, October 23, 2012

While I continue researching for my thesis project, I’m realizing more and more not to disregard ‘old’ articles just because they are, well, ‘old’. 3 articles by Partridge and colleagues from the 1980s have proven to be of great use to me in understanding costs associated with mating, and how choice influences all individuals in the equation (i.e. males, females and subsequent offspring.) The following are annotations for these articles: 

Fowler, K. & Partridge, L. 1989. A cost of mating in female fruit flies. Nature 228:760-761.
This article looks at the costs a female endures when mating with a male in the model organism Drosophila melanogaster. This is done through mating experiments where virgin females were subjected to either a group of males who all were capable of mating (high-mating) or a group of males where only one of the males was actually capable of mating (low-mating). Males in the low-mating scenario still displayed courting behaviours towards females, but had genitalia removed so they could not actually mate. Results showed that the females who were exposed to high-mating scenarios had significantly lower life spans then those exposed to low-mating. Although this may be a consequence of injury, parasites, or effects of sperm, it still is related to the actual process of mating. These results therefore have profound effects on the future reproduction success of these females. These conclusions are beneficial for me to understand in order to predict then why a female may alter her investment in the subsequent offspring, depending on the costs she has endured through mating.

 Partridge, L. 1980. Mate choice increases a component of offspring fitness. Nature 283:290-291.
In this experiment, larval survival rates are used as a measure of D. melanogasters’ offspring fitness. Males and females are exposed to treatments in which they have the ability to choose mates (cages with many individuals), or where they are unable to choose their mate (randomly selected female exposed to single randomly selected male).  Results show higher fitness in subsequent offspring (i.e. more offspring when exposed to competing larvae) of parents who did have choice in who they mated with, compared to those who did not. The author discusses possibilities of the genetics of these individuals influencing choice, and how if there are differences in paternal and maternal genes, it can lead to fitter offspring because of heterozygosity. This information is relevant to my research, because it is important to understand the how the identity of the parents can have a significant affect on their offsprings’ fitness, especially since the flies in my experiment are exposed to a no-choice treatment.
Partridge, L. & Farquhar, M. 1981. Sexual activity reduces lifespan of male fruit flies. Nature 294:580-581.
Partridge and Farquhar study how mating affects the fruit flies’ lifespan by exposing males (Drosophila melanogaster) to different numbers of receptive females and comparing their longevity with control groups. Males in experimental groups were exposed to 1-8 virgin females a day, while males in the control groups were exposed to females who had already been inseminated and therefore would not remate, or with no females at all. Males exposed to the highest number of receptive females (i.e. 8 virgins per day) were shown to have the lowest longevity compared to males who were exposed to fewer receptive females (slightly higher longevity), and control groups (greatest longevity). Understanding the costs associated with mating can help us to understand differences in parental investment of their offspring.

Although these articles are not exactly directly related to my research, the basis of mate choice and affect on all of the individuals involved is very useful background knowledge to have. It allows me to better understand costs of mating behaviours, and hypothesize therefore why differences in parental investment based on the identity of mates may have adaptive benefits.

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