Variable host quality, life-history invariants, and the reproductive strategy of a parasitoid wasp that produces single sex clutches |
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Authors: | West S A; Flanagan K E; Godfray H C J |
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Institution: | a
Natural Environment Research Council Centre for Population Biology and
Department of Biology, Imperial College, Ascot, Berkshire SL5 7PY, UK
b
Institute of Cell, Animal and Population Biology, University of Edinburgh, EH9
3JT, UK |
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Abstract: | The parasitic wasp Achrysocharoides zwoelferi (Hymenoptera,
Eulophidae) produces clutches consisting of only one sex. Moreover,male clutch size is invariably one while female clutches arein the range one to four. We designed field experiments todetermine the effect of host quality on clutch composition.We found that solitary male and solitary female clutches werereared from the same size mines, and that larger mines tendedto produce gregarious female clutches. A higher proportionof male clutches were placed in older hosts, despite theirlarge size. Variation in body size, both between and withinclutches, was measured in order to test the predictions of models
that take into account the constraint that clutch size is aninteger trait, something of potential importance when absoluteclutch size is low. Our data supported several predictionsof these models, including the trade-off-invariant rule foroptimal offspring size developed by Charnov and Downhower.However, while most invertebrate clutch size models assume equal
resource share among members of the same clutch, we found anincrease in inequality in larger clutches. |
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Keywords: | body size clutch size Hymenoptera sex allocation sex ratio trade-off |
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