Evol Ecol Res 14: 343-352 (2012)     Full PDF if your library subscribes.

Experimental demonstration of a ‘rate–size’ trade-off governing body size optimization

John P. DeLong

Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA

Correspondence: J.P. DeLong, School of Biological Sciences, University of Nebraska, Lincoln, NE 68588, USA.
e-mail: jpdelong@unl.edu


Questions: Can the decline in ectotherm body size with increasing temperature be explained using a simple body size optimization model? Does the pattern conform to the rate–size trade-off wherein organisms trade asymptotic size for mass-specific resource demand in order to maintain maximal resource uptake rates?

Organism: The predatory protist, Actinosphaerium sp., feeding on Paramecium bursaria.

Methods: I measured biovolume production rate (an index of mass-specific resource demand) and cell size across three environmental temperatures. I controlled prey supply by mixing and standardizing culture media across treatments and replicates.

Results: Biovolume production rates increased and cell size decreased with increasing temperature. The slope between these two variables on logarithimic axes (−0.91) was almost exactly as predicted by the optimization model (−0.94), lending quantitative support for the existence of a rate–size trade-off that governs the plasticity of size in this species and leads to the temperature–size rule.

Keywords: Actinosphaerium, body size evolution, life-history evolution, Paramecium bursaria, supply–demand model, temperature–size rule.

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