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The temperature-size rule in ectotherms: simple evolutionary explanations may not be general.
Michael J Angilletta1, Arthur E Dunham
1Department of Life Sciences, Indiana State University, Terre Haute, Indiana 47809, USA. m-angilletta@indstate.edu
The American Naturalist
|September 13, 2003
Summary
Organisms grow larger in colder environments, but growth efficiency doesn't decrease with temperature as predicted. This challenges the temperature-size rule, suggesting other factors like developmental constraints may influence body size.
Area of Science:
- Ecology
- Evolutionary Biology
- Physiology
Background:
- Bergmann's rule and the temperature-size rule explain why organisms are larger in colder climates.
- Theory suggests lower growth efficiency at higher temperatures drives this pattern.
Purpose of the Study:
- To test the prediction that growth efficiency decreases with increasing environmental temperature.
- To investigate the relationship between environmental temperature and growth efficiency in ectotherms.
Main Methods:
- Meta-analysis of 97 laboratory experiments.
- Inclusion of data from 58 ectotherm species.
- Analysis of gross and net growth efficiency across thermal ranges.
Main Results:
- Little evidence was found that growth efficiency is negatively related to environmental temperature.
- In most cases (73/89 for gross, 18/24 for net), growth efficiency was positively related or insensitive to temperature.
- Thermal optima for growth efficiency and rate decreased with individual growth.
Conclusions:
- The established theory explaining temperature-size relationships may be incomplete.
- Developmental constraints at higher temperatures, particularly later in ontogeny, could be a significant factor.
- Future research should explore organism-specific theories for temperature-body size relationships.