Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Biology

Supervisor

Moehring, Amanda J.

Abstract

Species can arise as a result of reproductive barriers that prevent gene flow between diverging populations that force them to remain isolated from one another. Behavioural isolation is one of the earliest acting reproductive barriers determined by the evolution of mating preferences that prevent inter-specific matings. Several traits have been identified that contribute to behavioural isolation, but the genetic basis of interspecific female preference is yet to be determined. I used genetic mapping techniques to identify and confirm that the fruitless gene is affecting species-specific female rejection of interspecies males, contributing to the behavioural isolation between Drosophila melanogaster and D. simulans. I also determined that this species-specific female preference is caused by a non-sex specifically spliced transcript of fruitless. Transgenic rescue of fruitless expression using the GAL4/UAS system identified fruitless protein isoforms with a specific 3’ C-terminal end are likely involved in species-specific female preference. Additionally, I discovered that female rejection of interspecies males is not determined by an individual sensory modality such as male courtship song or female perception of auditory and olfactory signals, and is likely controlled by the integration of multiple modalities. Finally, I constructed transgenic RNAi lines to silence expression of specific D. melanogaster or D. simulans fruitless transcripts. These RNAi lines can be used to knockdown fruitless expression at specific developmental stages and in specific tissues using the GAL4/UAS system, and thus can be a useful tool for characterizing the genetic and neural mechanisms that govern species-specific female rejection.

Summary for Lay Audience

Species are maintained as distinct groups by reproductive barriers that prevent interbreeding. Behavioural Isolation is one such reproductive barrier that acts via the incompatibilities in mating signals and preferences between diverged population groups. Our current understanding of the genetic mechanisms for behavioural isolation is limited. My research identifies the fruitless gene in Drosophila as a candidate gene for behavioural isolation. Through a series of genetic and molecular biological experiments I established that the fruitless gene is influencing female preference for mates within its own species, which is the first reported behavioural role in females for this gene. I also identified potential molecular and genetic mechanisms by which this gene is affecting female mating behaviour and contributing to the behavioural isolation observed between different species of Drosophila.

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