Thesica.org, the #1 open access web portal for PhD theses...

Why PhD theses...

PhD thesis is the result of years of hard work.

keyword researchMeasured by download count PhD theses are one of the most popular items world wide on open access repositories. But unless a thesis is published, it is very difficult for other researchers to find out about it and get access to it. Theses are often under-used by other researchers. Thesica.org attempts to address this issue by making it easy to identify and locate copies of many theses in various disciplines.

Life-history evolution in the parasitoid wasp Nasonia vitripennis

Life-history evolution in the parasitoid wasp Nasonia vitripennis
EDWARD MATHISON SYKES

2007

The University of Edinburgh and Department of Zoology, Oxford Unversity, Oxford OX1 3PS, UNITED KINGDOM.

ABSTRACT

Reproductive success is heavily influenced by life-history traits; a series of energy investment trade-offs that organisms must optimise according to their environmental conditions. These include considerations such as how many offspring and when to reproduce? The consequences of multiple trade-offs can be extremely complex, making research difficult. However, there are notable exceptions. Simple clutch size theory enabled great strides in assessing trade-offs in resource allocation, though it quickly becomes more complicated when considering investment in current versus future reproduction. Arguably, even greater success has come from consideration of investment in a particular sex. Sex allocation theory provides simple models that can be empirically tested, and has provided some of the strongest evidence for natural selection and evolution. Much of this work has focused on certain parasitoids due to their extraordinary sex ratios and the finite resources available to offspring in a host. Whilst clutch size and sex allocation theory have provided many answers, there are still questions regarding the impact of other life-history traits. In this thesis I have used the gregarious parasitoid wasp Nasonia vitripennis in laboratory experiments to assess some of these traits. I have focused on the impact of larval competition, inbreeding, host condition and host feeding on longevity, fecundity, sex allocation and mating success. By manipulating host quality through host-feeding, I was able to vary the level of resources available to offspring. Simultaneously, by manipulating the matedstatus and number of females ovipositing on a host, I was able to vary the number and sex ratio of offspring competing for resources. My research has provided an insight into how larval competition and host-feeding impact on optimal clutch size and sex allocation. Furthermore, I have attempted to assess the extent to which body size, which is commonly associated with reproductive success, can be used to predict fitness. The appendix includes work using molecular data to understand the mating behaviour and population structure of N. vitripennis in the wild, enabling models based on assumptions of laboratory-based behaviour to be applied to wild populations.