The pay-off from superparasitism in the egg parasitoid Trissolcus basalis, in relation to patch defence |
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Authors: | SCOTT FIELD MICHAEL KELLER & GREG CALBERT |
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Institution: | Department of Crop Protection, University of Adelaide, Australia, ,;Department of Applied Mathematics, University of Adelaide, Australia. |
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Abstract: | 1. In species such as quasi-gregarious egg parasitoids, which exploit defendable patches, the fitness pay-off from superparasitism is an important factor in considering the evolution of patch defence and optimal patch defence strategies. 2. When oviposition in a previously parasitized host has a non-zero fitness pay-off, competing parasitoids are not only able to diminish the future value of a patch to other females by depleting unparasitized hosts, but also devalue the previous investment of other females in the patch by superparasitizing. 3. In Trissolcus basalis , an egg parasitoid of pentatomid bugs, the fitness pay-off from superparasitism is higher than 0.5 when the time interval between ovipositions is less than 3 h, suggesting that defending a previous investment will be an important component of patch defence behaviour. 4. The data suggest a mechanism for the high early pay-off, which involves the superparasitizing female adjusting the sex ratio of its offspring in favour of males. Males develop more quickly than females and thus may have a competitive advantage. |
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