A Comparative Study of Sex Ratio and Clutch Size in Gregarious Ichneumonoid Wasps |
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Authors: | Christina B Smart Peter J Mayhew |
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Institution: | (1) Department of Biology, University of York, P.O. Box 373, York, YO10 5YW, UK |
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Abstract: | Some convincing support for sex ratio theory comes from the cross-species relationship between sex ratio and brood size in
gregarious bethylid wasps (Hymenoptera: Bethylidae), in which the proportion males declines as brood size increases as predicted
under local mate competition. It is unknown how widely such relationships hold within parasitoid wasps as a whole. We assemble
a dataset on sex ratio and brood size for gregarious Braconidae and Ichneumonidae. Their sex ratios deviate substantially
from those of bethylids; sex ratios differ widely across species; and they are not significantly related to brood size across
species. Several factors explain the heterogeneity in sex ratios including across-species differences in mating system, sex
determining mechanism, and sexual asymmetries in larval competition and polyembryony leading to single-sexed broods. |
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Keywords: | Bethylidae Braconidae Ichneumonidae local mate competition mating structure sex ratio theory |
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