Within-group conflict (whether that group is an ant colony, an organism or a genome) has been identified as an important evolutionary force. Indeed, it is somewhat paradoxical that groups are able to operate in the face of such conflict. The problem is that selfishness is frequently the best option for thelower level unit. For example, genes that gain an ‘unfair’ transmission advantage, or worker bees that lay male eggs (so neglecting their colony duties), are expected to have the edge over their co-operative colleagues. The fact that actual conflict emerges far less frequently than theory predicts, suggests thatthere are mechanisms at the group level to keep lower level units in check. Such mechanisms, it is claimed, may have evolved in response to the appearance of ‘selfish’ variants. In this thesis, I examine some of these claims in more detail. For example, did meiosis and anisogamy evolve in response to theinvasion of particular ‘selfish’ genetic elements? I show that in both cases this seems unlikely. In the case of anisogamy there are numerous other suggestions for the selective advantages of gamete dimorphism. I describe the first phylogenetically controlled, comparative test of the dominant explanation and critically review the others. One consequence of anisogamy is that it opens up a further arena for conflict between nuclear and cytoplasmic genes. Male-killing parasites are one manifestation of such conflict. I investigate some of the consequences of these parasites for host evolution. In particular I explore, theoretically, the evolution of host resistance and of host mating systems in response to male-killer invasion. While I find that the presence of a male-killer can, in theory, impose selection for male mate-choice, field data suggestthat this explanation does not apply in the case of an East African butterfly.
|Date of Award||1 Dec 2001|
|Supervisor||Laurence Hurst (Supervisor)|