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Thermal and energetic constraints on ectotherm abundance: a global test using lizards.

TitleThermal and energetic constraints on ectotherm abundance: a global test using lizards.
Publication TypeJournal Article
Year of Publication2008
AuthorsBuckley LB, Rodda GH, Jetz W
Date Published2008 Jan
KeywordsAnimals, Body Temperature Regulation, Body Weight, Energy Metabolism, Lizards, population density, Population Dynamics, Population Growth, Temperature

<p>Population densities of birds and mammals have been shown to decrease with body mass at approximately the same rate as metabolic rates increase, indicating that energetic needs constrain endotherm population densities. In ectotherms, the exponential increase of metabolic rate with body temperature suggests that environmental temperature may additionally constrain population densities. Here we test simple bioenergetic models for an ecologically important group of ectothermic vertebrates by examining 483 lizard populations. We find that lizard population densities decrease as a power law of body mass with a slope approximately inverse to the slope of the relationship between metabolic rates and body mass. Energy availability should limit population densities. As predicted, environmental productivity has a positive effect on lizard density, strengthening the relationship between lizard density and body mass. In contrast, the effect of environmental temperature is at most weak due to behavioral thermoregulation, thermal evolution, or the temperature dependence of ectotherm performance. Our results provide initial insights into how energy needs and availability differentially constrain ectotherm and endotherm density across broad spatial scales.</p>

Alternate JournalEcology