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Endotherms, ectotherms, and mitochondrial genome-size variation
1Graduate Program in Ecology and Evolution, Brown University, Providence, RI 02912.
Journal of Molecular Evolution
|September 1, 1993
Summary
Endotherms exhibit less mitochondrial DNA (mtDNA) size variation than ectotherms, suggesting thermal habit influences animal mtDNA evolution. This finding supports selection for smaller genomes in species with higher metabolic rates.
Area of Science:
- Evolutionary Biology
- Genetics
- Zoology
Background:
- Animal mitochondrial DNA (mtDNA) size variation is influenced by various factors.
- Thermal habit (endothermy vs. ectothermy) is a potential driver of evolutionary changes in mtDNA.
Purpose of the Study:
- To investigate patterns of mitochondrial genome-size variation in endothermic and ectothermic species.
- To examine the role of thermal habit in the evolution of animal mtDNA.
Main Methods:
- Tabulated data on mtDNA size (modal, largest, smallest), percent variation, and heteroplasmy frequency from existing literature.
- Compared these metrics between endothermic and ectothermic species, including vertebrates.
Main Results:
- Endotherms displayed significantly less mtDNA size variation and generally smaller mtDNAs compared to ectotherms.
- Endothermic vertebrates had significantly smaller largest genomes and lower percent genome size variation than ectothermic vertebrates.
- No significant difference in heteroplasmy frequency was observed between endotherms and ectotherms.
Conclusions:
- Observed trends support the hypothesis of stronger selection for smaller mtDNA genome size in endotherms due to higher metabolic rates.
- In some species, mtDNA size variation may be influenced by mutational pressures rather than selection alone.
- Further comparative studies on sister taxa and tissues with differing metabolic rates are proposed to elucidate these hypotheses.