Sexual selection in stalk-eyed flies; inbreeding depression, sperm competition and larval development.
Doctoral thesis, UCL (University College London).
Stalk-eyed flies (Diptera: Diopsidae) have emerged as an important model organism in the study of sexual selection. They are characterised by their eyes being located on elongated stalks that protrude from their heads. In many species, males have larger eyespans than females as a result of female mate preference and malemale competition. In this thesis, I investigated several different aspects of stalk-eyed fly biology. First, I provide a comprehensive review that asks whether the literature supports the hypothesis that male sexual traits suffer from heightend inbreeding depression relative to non-sexual traits. This is followed by an empirical study that examines how inbreeding affects a sexual trait (male eyespan) relative to non-sexual traits (female eyespan and male wing length) in the stalk-eyed fly Diasemopsis meigenii. Sexual selection theory predicts that sexual traits should suffer greater inbreeding depression than non-sexual traits. Full-sibling matings were used to generate highly inbred lines of D. meigenii. Over 11 generations of inbreeding, male eyespan suffered more from inbreeding depression than female eyespan and male wing length. After crossing inbred lines, male eyespan was restored more than male wing length, but not female eyespan. Next, I used a P2 mating design to test male offence and defence roles in sperm competition. Female D. meigenii were mated once by a ‘focal male’ and n times by a ‘competing male’ (where n = 1, 3 or 5). Male defence and male offence ability was assessed by mating the focal male either before or after the competing male. I found no evidence of sperm precedence in D. meigenii and suggest that the most likely mechanism of sperm competition is via mixing of sperm from rival males. Finally, I examine how adult sexual size dimorphism in the stalk-eyed fly Teleopsis dalmanni is determined and regulated during larval development.
|Title:||Sexual selection in stalk-eyed flies; inbreeding depression, sperm competition and larval development|
|Additional information:||Permission for digitisation not received|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Life Sciences > Biosciences (Division of) > Genetics, Evolution and Environment|
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