A general model for the scaling of offspring size and adult size

Daniel S. Falster, Angela T. Moles, Mark Westoby

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)
87 Downloads (Pure)


Understanding evolutionary coordination among different life-history traits is a key challenge for ecology and evolution. Here we develop a general quantitative model predicting how offspring size should scale with adult size by combining a simple model for life-history evolution with a frequency-dependent survivorship model. The key innovation is that larger offspring are afforded three different advantages during ontogeny: higher survivorship per time, a shortened juvenile phase, and advantage during size-competitive growth. In this model, it turns out that size-asymmetric advantage during competition is the factor driving evolution toward larger offspring sizes. For simplified and limiting cases, the model is shown to produce the same predictions as the previously existing theory on which it is founded. The explicit treatment of different survival advantages has biologically important new effects, mainly through an interaction between total maternal investment in reproduction and the duration of competitive growth. This goes on to explain alternative allometries between log offspring size and log adult size, as observed in mammals (slopep0.95) and plants (slopep0.54). Further, it suggests how these differences relate quantitatively to specific biological processes during recruitment. In these ways, the model generalizes across previous theory and provides explanations for some differences between major taxa.

Original languageEnglish
Pages (from-to)299-317
Number of pages19
JournalAmerican Naturalist
Issue number3
Publication statusPublished - Sept 2008

Bibliographical note

Copyright 2008 by University of Chicago Press. Originally published in the American naturalist.


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