Fitness components of small and large males (emerging respectively from small and large hosts) of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) were compared in laboratory experiments. These components were the longevity, courtship, mate competition, and daily and lifetime fertilization. Small males were less fit than large males: they had a reduced longevity, took longer to induce female mating behavior, rarely succeeded in mating females when in competition with large males and had lower fertilization capacity; female fertilized by small males oviposited in the first two days of their life only one third of the progeny of daughters mated by large males. The impact of males fitness on optimal sex allocation by females parasitoids was evaluated by measuring the primary and tertiary sex ratios (proportion of males in the progeny) produced by a female T. evanescens when ovipositing in small and large hosts (low and high quality patches). Females of T. evanescens, an arrhenotokous species, have control on the sex ratio of their offspring by regulation of the sperm's access to the egg. Certain combinations of male and female eggs deposited in a host patch result in greater fitness than others. As predicted, females produced a significantly higher proportion of males on the low quality patches. T. evanescens females adjusted the sex ratio allocated to a patch of homogeneous quality and under complete local mate competition to the expected fitness of their sons, as smaller males have a lower fitness and are expected to have low fertilization capacity and therefore fertilize less females. To optimize her fitness gain (the capacity of the individual to transmit its genes), the sex ratio is increased in order to have all daughters mated.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.20830 |
| Date | January 1998 |
| Creators | Lagacé, Martine. |
| Contributors | Boivin, Guy (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Natural Resource Sciences.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001610283, proquestno: MQ44200, Theses scanned by UMI/ProQuest. |
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