Sex allocation and larval competition in a superparasitizing solitary egg parasitoid: competing strategies for an optimal sex ratio |
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Authors: | J. Van Baaren,B. L. Landry,& G. Boivin |
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Affiliation: | Centre de Recherche et de Développement en Horticulture, Agriculture et Agro-alimentaire Canada, 430 Boul. Gouin, St-Jean-sur-Richelieu, Québec, Canada J3B 3E6,,;UMR no. 6552, Ethologie, Evolution, Ecologie, Universitéde Rennes I, France, and,;DNA LandMarks Inc., C.P. 6, St-Jean-sur-Richelieu, Québec, Canada J3B 6Z1 |
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Abstract: | 1. Parasitic Hymenoptera reproduce by arrhenotokous parthenogenesis, and females of these species are able to control their progeny sex ratios. In structured populations of parasitic Hymenoptera, primary sex ratios are often highly biased toward females. However, sex ratio can be adjusted to the quality of encountered patches or hosts or be modified by differential developmental mortality. 2. In this paper, the effects were evaluated of the quality of encountered hosts and developmental mortality on the sex ratio in Anaphes victus , a solitary egg parasitoid whose first instar larvae present a sexual dimorphism and where superparasitism is regulated by larval fights between first instar larvae. 3. The results showed that a female-biased sex ratio is allocated to unparasitized hosts. In the presence of parasitized hosts, the second (superparasitizing) female produced a significantly higher sex ratio than the first female but the tertiary sex ratio (sex ratio at emergence) was not significantly different from the sex ratio produced with unparasitized hosts. The increase in the primary sex ratio produced by the second female was mostly compensated by the higher mortality of male larvae. |
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Keywords: | Anaphes male–female competition Mymaridae primary and tertiary sex ratio |
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