Evol Ecol Res 7: 779-794 (2005)     Full PDF if your library subscribes.

Testing predictions of small brood models using parasitoid wasps

Meghan A. Guinnee,1* Julio S. Bernal,2 T. Martijn Bezemer,3 Jeffery G. Fidgen,4 Ian C.W. Hardy,5 Peter J. Mayhew,6 Nicholas J. Mills7 and Stuart A. West1

1Institutes of Evolution, Immunology and Infection Research, University of Edinburgh, Edinburgh, UK,  2Biological Control Laboratory, Texas A&M University, College Station, TX, USA,  3Department of Multitrophic Interactions, NIOO-CTO, Heteren, The Netherlands,  4Department of Entomology, Virginia Tech, Blacksburg, VA, USA,  5School of Biosciences, University of Nottingham, Loughborough, UK,  6Department of Biology, University of York, York, UK and  7University of California, Berkeley, CA, USA

Address all correspondence to Meghan A. Guinnee, Buffalo Museum of Science, 1020 Humboldt Parkway, Buffalo, NY 14211, USA.
e-mail: meghan.guinnee@gmail.com


Question: How is variation in offspring size (between broods) related to brood size?

Hypotheses: Variance in offspring size (between broods) should decrease with increasing brood size as predicted by Charnov and colleagues’ (Charnov and Downhower, 1995; Charnov et al., 1995) small brood invariant. The range in resources put towards reproduction (for mothers producing a certain brood size) should be invariant over brood size (Downhower and Charnov, 1998). We also test assumptions underlying these predictions.

Data studied: We use previously collected data on six parasitoid wasp species.

Conclusions: As predicted, variance in offspring size among broods decreased with increasing brood size. However, this decrease did not follow closely the quantitative predictions of Charnov and colleagues (Charnov and Downhower, 1995; Charnov et al., 1995). We found some support for the prediction that the range in resources invested in reproduction is invariant over brood size. The assumption that mean offspring size is constant over brood size was violated in three of six species. The assumption that resources are shared equally between individuals within a brood generally held.

Keywords: brood size, litter size, parasitoid wasps, resource allocation, trade-off.

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