1. The function and evolutionary ecology of intra-sexual aggression in Drosophila melanogaster
- Author
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Edmunds, Danielle, Pizzari, Tommaso, Wigby, Stuart, and Perry, Jennifer
- Subjects
591.56 ,Kin recognition in animals ,Nutrition ,Aggressive behavior in animals ,Sexual selection in animals - Abstract
Across the animal kingdom, competition for reproductive resources often results in intra-sexual aggressive contests. The extent to which individuals engage in aggression varies in response to ecological conditions. However, as individuals live and compete in highly complex environments, understanding how aspects of an individual's ecological surroundings shape aggression is a constantly advancing field with many unresolved questions. Furthermore, while much previous research has focused on male aggression, it is now acknowledged that females fight too, but whether female aggression reflects male aggression in its response to the environment is largely unknown. In this thesis, I use the fruit fly, Drosophila melanogaster, to investigate how the prevailing environment drives short term responses and long term evolutionary change in aggression in both sexes. Sexual selection plays a key role in shaping traits involved in reproductive competition, such as aggression, and I begin by investigating how the sex ratio influences the operation of sexual selection in males, and whether these patterns are reflected in females. Traditional sexual selection theory predicts that as the sex ratio becomes more biased, the abundant sex should experience stronger sexual selection. I find support for this prediction in males, but, in females, I find sexual selection arising from mating competition to be weak and insensitive to the sex ratio, illustrating differences in intra-sexual competition in the two sexes. I then investigate how aggression evolves in response to the population sex ratio, and find that a male-biased sex ratio increases the propensity for males to focus aggression around food patches but does not influence male aggressive intensity, while a female-biased environment increases the magnitude by which mating elevates female aggression. Furthermore, kin selection has the potential to shape aggressive interactions, and high population relatedness can reduce harmful aggressive behaviours. I find some evidence that high relatedness can reduce harmful behaviours in D. melanogaster, but find this response to be highly sensitive, with no evidence that it is driven solely by olfactory-based discrimination. Finally, I show that nutrition can determine aggressive ability and motivation, with aggression decreasing in response to food deprivation during development but increasing in response to adult food deprivation.
- Published
- 2020