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Local Mate Competition, and Mechanisms, Functions and Fitness Consequences of Courtship and Mating Behaviour in the Parasitoid Wasp Ooencyrtus kuvanae
(Hymenoptera: Encyrtidae)

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Thesis type
(Dissertation) Ph.D.
Date created
Males and females of the egg parasitoid wasp Ooencyrtus kuvanae (Howard) (Hymenoptera: Encyrtidae) emerge as sexually mature adults from gypsy moth, Lymantria dispar (L.), host egg masses. Sibling or non-sibling males compete intensely for mating opportunities with spatially clustered monandrous females who are briefly receptive. Mated females typically disperse prior to ovipositing, whereas males disperse in search of mates. My main objectives were to examine the occurrence of local mate competition (LMC), and to tease apart the mechanisms, functions, and fitness consequences of courtship and mating behaviour in O. kuvanae. As predicted by LMC theory, with increasing numbers of foundresses on a host egg mass, the proportion of emerging males increases. Males exhibit one of two mating tactics, a mate-at-once (MAO) tactic, and a harem-gathering and -guarding (HGG) tactic. MAO males immediately mate any receptive female they encounter. HGG males mate the first receptive female they encounter, then transfer a unique pheromone-tag to females without prior male contact, and finally relocate and mate those females they themselves have tagged. Females do not incur direct fitness costs by mating with multiply-mated males. Males are attracted to a close-range female sex pheromone comprising (5S)-methylheptacosane and (5R,17S)-dimethylheptacosane. Conversely, males are repelled by the blend of (5R)-methylheptacosane and (5R,17R)-dimethylheptacosane. This suggests that the stereochemistry of these two hydrocarbons may differ between males and females, and that it could be an underlying mechanism in mate recognition and mate assessment. Immediately prior to copulation, males engage females in a brief pre-copulatory ritual, then mate, and thereafter execute a lengthier post-copulatory ritual. Both rituals entail physical interactions rather than pheromone transfer. Following the pre-copulatory ritual, females enter a receptive state that persists after copulation, whereby a female is susceptible to additional copulations by sneaker males, who compete with the first male to mate for post-copulatory ritual rites. The post-copulatory ritual accelerates the awakening of an in-trance female, who then never mates again. First male sperm precedence lies with the first male to engage a female in the post-copulatory ritual. Therefore, the ritual may represent a male adaptation to prevent sperm competition.
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Thesis advisor: Gries, Gerhard
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