Despite the benefits of sexual reproduction, sharing a genome can put constraints on the evolvability of a species. This is due to sexual conflict, where the interests of each sex is in direct opposition to one another, and the benefit of one sex can be the cost of the other sex (i.e. sexual antagonism). Sex chromosomes have been the focus of much of the research done on sexual conflict due to their unique nature and are particularly interesting in the context of sexually antagonistic variance. In the first experiment (Chapter 2), I used experimental evolution to investigate the standing sexually antagonistic variation on the X-chromosome of the common vinegar fly, Drosophila melanogaster. Unlike most other experimental evolution experiments where selection has been limited to males, I limited the inheritance of the X-chromosome to females only. I used a non-recombining Xchromosome balancer to control the inheritance of the female-limited X-chromosome. Throughout the evolution experiment, I tested different phenotypic traits that have previously been shown to be sexual antagonistic, as well as investigating how the transcriptome changed through female-limited selection (Chapter 3). The results were mixed but indicated that limiting selection of the X-chromosome to females could, to some extent, change the antagonistic variation and move traits towards the female optimum. In the second experiment (Chapter 4), I exchanged sex chromosomes between populations with divergent geographic origins. I used flies with special genetic constructs (e.g. autosomal balancers, fused-X chromosomes) to control the population crosses, so that sex chromosomes were introduced into a new background without any prior interaction. I found that introducing a novel sex chromosome increased male reproductive fitness through improved sperm competition at the cost of offspring viability. 25 generations after introducing the novel sex chromosome (Chapter 5), the increase in male fitness was undetectable and their fitness was again the same as the wild types. Collectively, this indicates an antagonistic coevolution between the sex chromosomes. Together, these two experiments shed new light on sexual conflict and the antagonistic coevolution between the sexes at the genetic level, both between and within the sex chromosomes. These novel insights could help further the understanding of how sex chromosomes may affect speciation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:723086 |
| Date | January 2017 |
| Creators | Lund-Hansen, Katrine Koch |
| Publisher | University of Sussex |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://sro.sussex.ac.uk/id/eprint/70184/ |
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