Evol Ecol Res 8: 1409-1425 (2006)     Full PDF if your library subscribes.

Modelling the energy–mortality trade-offs of invertebrate decorating behaviour

Sarah K. Berke,1* Matthew Miller2 and Sarah A. Woodin1

1Department of Biological Sciences and  2Department of Mathematics, University of South Carolina, Columbia, SC 29208, USA

Address all correspondence to Sarah K. Berke, Department of Biological Sciences, University of South Carolina, 701 Sumter Street, Columbia, SC 29208, USA.
e-mail: berke@biol.sc.edu


Background: Animals belonging to nearly 25% of the major metazoan phyla ‘decorate’ themselves with foreign material. Decoration occurs frequently in some taxa but infrequently in others. Some data indicate that decoration is a morphologically flexible phenotype that facilitates feeding and/or protects against biotic and abiotic forces. Yet decoration is not taxonomically ubiquitous. Other data suggest that decorating could be energetically costly.

Questions: How do feeding, energy expenditure, and mortality risk interact to exert selective pressure on decorating phenotypes? Could energetic costs associated with decorating theoretically limit the behaviour’s selective advantage and account for its patchy taxonomic distribution?

Methods: Build a model of decoration’s effect on reproductive potential using energy intake, energy expenditure, and mortality risk as parameters. Analytically find the upper bound of permissible energetic costs. From existing literature, estimate parameter values for energetics, reproduction, and mortality of the green sea urchin, Strongylocentrotus droebachiensis, and analyse them using graphical and numerical methods to determine the probable influence of energy cost on decoration in this animal.

Conclusions: Physiologically realistic energetic costs can constrain the parameter space in which decorating is selectively advantageous. This appears to be true even for costs far below the theoretical upper limit. Thus the evolution of decoration should be more sensitive to energetic costs than to the other parameters that we modelled. Sensitivity to energetic costs may explain (at least in part) decoration’s patchy taxonomic distribution.

Keywords: camouflage, covering, defence, ornamentation, masking, predation, reproductive potential, selection.

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        © 2006 Sarah K. Berke. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

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