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Appears in Collections:Biological and Environmental Sciences Journal Articles
Peer Review Status: Refereed
Title: Offspring size variation within broods as a bet-hedging strategy in unpredictable environments
Author(s): Marshall, Dustin J
Bonduriansky, Russell
Bussiere, Luc
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Keywords: egg size
environmental variation
life history
marine invertebrates
maternal effect
offspring size–fitness
reproductive strategy
seed size
unpredictable environments
Issue Date: Sep-2008
Citation: Marshall DJ, Bonduriansky R & Bussiere L (2008) Offspring size variation within broods as a bet-hedging strategy in unpredictable environments, Ecology, 89 (9), pp. 2506-2517.
Abstract: Offspring size is strikingly variable within species. Although theory can account for variation in offspring size among mothers, an adaptive explanation for variation within individual broods has proven elusive. Theoretical considerations of this problem assume that producing offspring that are too small results in reduced offspring viability, but producing offspring that are too large (for that environment) results only in a lost opportunity for increased fecundity. However, logic and recent evidence suggest that offspring above a certain size will also have lower fitness, such that mothers face fitness penalties on either side of an optimum. Although theory assuming intermediate optima has been developed for other diversification traits, the implications of this idea for selection on intra-brood variance in offspring size have not been explored theoretically. Here we model the fitness of mothers producing offspring of uniform vs. variable size in unpredictably variable environments and compare these two strategies under a variety of conditions. Our model predicts that producing variably sized offspring results in higher mean maternal fitness and less variation in fitness among generations when there is a maximum and minimum viable offspring size, and many mothers under- or over-estimate this optimum. This effect is especially strong when the viable offspring size range is narrow relative to the range of environmental variation. To determine whether this prediction is consistent with empirical evidence, we compare within- and among-mother variation in offspring size for 5 phyla of marine invertebrates with different developmental modes corresponding to contrasting levels of environmental predictability. Our comparative analysis reveals that in the developmental mode in which mothers are unlikely to anticipate the relationship between offspring size and performance, size-variation within mothers exceeds variation among mothers, but the converse is true when optimal offspring size is likely to be more predictable. Together, our results support the hypothesis that variation in offspring size within broods can reflect an adaptive strategy for dealing with unpredictably variable environments. We suggest that when there is a minimum and a maximum viable offspring size and the environment is unpredictable, selection will act on both the mean and variance of offspring size.
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Rights: Copyright by the Ecological Society of America, Ecology, Vol. 89, No. 9, September 2008, pp. 2506-2517.

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Marshalletal Final Accepted.pdf430.2 kBAdobe PDFView/Open
Marshalletal Final Accepted.2.pdf65.54 kBAdobe PDFView/Open
Marshalletal Final Accepted.3.pdf170.26 kBAdobe PDFView/Open
Appendix A - Comparative details (1).pdf57.82 kBAdobe PDFView/Open
Appendix B.pdf59.62 kBAdobe PDFView/Open
Appendix C.pdf195.28 kBAdobe PDFView/Open

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