Intragenomic epistasis negatively impacts within-species coevolutionary arms races : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biological Sciences at Massey University, Albany, New Zealand
| dc.contributor.author | McFadyen, Sean Lewis | |
| dc.date.accessioned | 2024-12-08T22:28:19Z | |
| dc.date.available | 2024-12-08T22:28:19Z | |
| dc.date.issued | 2024 | |
| dc.description.abstract | Cooperation is susceptible to exploitation by selfish individuals. These individuals, referred to as cheaters, gain the benefits of cooperation without paying the costs. Cheating can select for individuals who can resist or prevent cheating, and resistance can in turn select for individuals that overcome the resistance. Thus, cheating and resistance potentially coevolve and lead to an arms race of adaptations and counter adaptations. Within a species, the existence of such an arms race is complicated by sexual reproduction among individuals that harbor alleles encoding the different strategies. Sexual reproduction will generate recombinants that harbor both cheating and resistance alleles. The impact of this recombination should depend on the extent of epistasis: that is, how the combined effects of these mutations differ from their effects individually. The goal of this thesis is to address how sexual reproduction impacts a within-species coevolutionary arms race, in this case, between cheating and resistance. The model organism Dictyostelium discoideum provides the perfect model to answer these questions. It has a unique life cycle, consisting of a unicellular (amoeba) stage, cooperative multicellular development (resulting in the formation of a fruiting body), and facultative sexual reproduction (resulting in the formation of a resting structure, termed a macrocyst). During the formation of the multicellular fruiting body, some cells are sacrificed to build a rigid stalk of dead cells that supports the rest. Cheaters exploit this altruistic sacrifice, and resistors prevent the cheaters from cheating. Resistance may in turn select for more efficient cheating, and this reciprocal selection can potentially spark a within-species arms race. During the sexual reproduction phase, recombination can then mix and match alleles encoding conflicting strategies into a single genetic background, allowing for epistatic effects to occur. Here I use the model organism Dictyostelium discoideum to understand how coevolution of cheating and resistance is impacted by sexual reproduction. To do so, I carried out a long-term evolution experiment to select for cheating and resistance. To understand the impact of recombination, I evolved replicate populations with or without periodic recombination. To address experimental difficulties, I also carried out an experiment to determine the optimal germination method for macrocysts produced during the Dictyostelium sexual cycle. Finally, I used computer simulations of the co-evolutionary process in Dictyostelium discoideum to explore how recombination and epistasis impact co-evolution, which allowed me to vary parameters of interest over a broader range of values than was possible in the laboratory. My findings suggest that recombination and resulting epistatic effects between conflicting strategies may prevent or slow within species co-evolutionary arms races. | |
| dc.identifier.uri | https://mro.massey.ac.nz/handle/10179/72228 | |
| dc.language.iso | en | |
| dc.publisher | Massey University | |
| dc.rights | The author | en |
| dc.title | Intragenomic epistasis negatively impacts within-species coevolutionary arms races : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biological Sciences at Massey University, Albany, New Zealand | |
| dc.type | Thesis |