Related Experiment Video
Updated: Jul 10, 2026
04:37
Reproductive Techniques for Ovarian Monitoring and Control in Amphibians
Published on: May 12, 2019
Amphibians do not follow Bergmann's rule
1Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa 50011, USA. dcadams@iastate.edu
Evolution; International Journal of Organic Evolution
|November 15, 2007
Summary
Bergmann's rule, which predicts larger body size in cooler climates, does not generally apply to amphibians. This study found little evidence for this pattern in Plethodon salamanders or amphibians overall.
Area of Science:
- Ecology
- Evolutionary Biology
- Zoology
Background:
- Bergmann's rule, a pattern of increasing body size with latitude or decreasing temperature, is well-established in endotherms.
- Its applicability to ectotherms, including amphibians, is debated, with conflicting evidence.
- Recent studies question the generality of Bergmann's clines in amphibians.
Purpose of the Study:
- To test for Bergmann's rule in Plethodon salamanders.
- To determine if body size clines are prevalent in amphibians.
- To investigate the relationship between body size and temperature across amphibian taxa.
Main Methods:
- Measured body size of 96,996 adult Plethodon from 3974 populations.
- Conducted phylogenetic comparative analyses.
- Performed a meta-analysis combining study data with existing amphibian data.
Main Results:
- Only 3 of 40 Plethodon species showed a pattern consistent with Bergmann's rule.
- Phylogenetic analysis revealed no significant relationship between body size and temperature among species.
- Meta-analysis across genera, orders, and classes of amphibians found no support for Bergmann's rule.
Conclusions:
- Bergmann's rule is not generally applicable to amphibians.
- Negative thermal body size clines are uncommon in this class.
- Evolutionary models for other tetrapods do not need to consider unique amphibian life histories regarding Bergmann's rule.
Related Concept Videos
01:51Lampbrush Chromosomes
In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, Rückert observed LBCs in shark egg cells and coined the term "lampbrush chromosomes" because they looked like brushes used to clean kerosene lamps.
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...
02:32Osmoregulation in Fishes
When cells are placed in a hypotonic (low-salt) fluid, they can swell and burst. Meanwhile, cells in a hypertonic solution—with a higher salt concentration—can shrivel and die. How do fish cells avoid these gruesome fates in hypotonic freshwater or hypertonic seawater environments?
02:27Background and Environment Affect Phenotype
Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as temperature, oxygen availability, presence of mutagens, that can alter an organism’s phenotype.
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
00:59Tonicity in Animals
The tonicity of a solution determines if a cell gains or loses water in that solution. The tonicity depends on the permeability of the cell membrane for different solutes and the concentration of nonpenetrating solutes in the solution within and outside of the cell. If a semipermeable membrane hinders the passage of some solutes but allows water to follow its concentration gradient, water moves from the side with low osmolarity (i.e., less solute) to the side with higher osmolarity (i.e.,...
02:29Hybrid Zones
Hybrid zones are narrow regions where two closely related species interact, mate, and produce hybrids. Relative to either parent species, hybrids may possess distinct phenotypic or genetic differences that impact their survival and reproductive success. The genetic variances introduced by hybridization influence species diversity and speciation processes within the hybrid zone.Gene flow and natural selection are evolutionary mechanisms that shape the outcome of a hybrid zone. Gene flow...
01:17Understanding Species and Reproductive Barriers
A species is a group of organisms that interbreed and produce fertile offspring. Typically, individuals of the same species appear similar and share common characteristics due to their highly similar genomes. However, not all organisms that look alike are members of the same species. Various mechanisms keep most species discrete. While some mechanisms prevent reproductive behavior and fertilization (pre-zygotic isolation), others prevent the production of fertile offspring after mating has...