Every generation, individuals acquire, on average, one new harmful mutation, not inherited from their parent. How populations are able to reduce their load of these mutations, and thus maintain positive population growth, is very poorly understood. Any type of selection will be more effective at improving the genetic fitness of populations when population size is large (and random chance is less influential). Some theories suggest that selection on males will be the most effective mechanism, but how is that applied? Similarly, if the effects of mutation load (e.g., early death, few offspring) are only observed in individuals with very high numbers of mutations, this would allow many mutations to be removed, with little effect on population size, relatively to a scenario where all individuals experienced somewhat depressed fitness. We investigate how selection acts to remove deleterious mutations, and gain a better understanding of how these processes might operate in natural populations that are faced with external pressures (e.g., loss of habitat) that drive a reduction in population growth, and  effectiveness of selection. The opportunity for natural selection (e.g., food competition, survival, offspring number) versus sexual selection (male or female mate choice) is easy to manipulation in our model organism, the native Australian vinegar fly, Drosophila serrata.

Supervisor: Dr Katrina McGuigan