Sexual selection and sex allocation in the gregarious parasitoid wasp Nasonia vitripennis
Abstract
Sex allocation and sexual selection have been heavily studied, but rarely linked. In
this thesis I investigated the interface between them in the gregarious parasitoid wasp
Nasonia vitripennis, both directly and through their interactions with the mating
system and sexual conflict. Chapter 2 investigated sexual selection and mating at the
natal site: earlier eclosing males mated more females independently of body size.
Nasonia follows Local Mate Competition, which describes how a female laying eggs
alone on a patch of resources (a so-called single-foundress) should lay an extremely
female-biased brood to minimise competition between her sons, yet ensure all her
daughters are fertilised. Based on this I predicted that males with with fewer brothers
would be better inseminators. Despite finding significant among-strain variation in
(1) single-foundress sex ratio, (2) mate competitiveness when alone and (3) when in
competition, (4) sperm resources, but not (5) sperm-depletion (Chapters 3 & 4), I did
not find the predicted relationship. Conversely males from strains with more brothers
had a higher mating success under competition (Chapter 3) leading to the question:
does mating success select on sex ratio or vice versa? Either way it is a result of an
interaction between sexual selection and sex allocation. Chapter 5 investigated the
role of male post-copulatory courtship on female re-mating, and found that among-strain variation in female re-mating was not associated with variation in the duration
of the post-copulatory courtship. Chapter 6 reviewed sexual conflict in the
Hymenoptera: their haplodiploid genetics, newly sequenced genomes and varied life-histories provides a base for future research to build on. Finally I highlight the novel
links between sexual selection, sex allocation, sexual conflict and the mating system
found during my studies that will hopefully prompt future research on this topic.
Type
Thesis, PhD Doctor of Philosophy
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