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Extant mammal body masses suggest punctuated equilibrium
Tiina M Mattila1, Folmer Bokma
1Department of Ecology and Environmental Sciences, Umeå University, 90187 Umeå, Sweden.
Proceedings. Biological Sciences
|July 4, 2008
Summary
Microevolutionary changes within species contribute little to macroevolutionary differences between species. This study suggests gradual evolution accounts for a small fraction of mammal body size variation.
Area of Science:
- Evolutionary biology
- Paleontology
- Mammalian biology
Background:
- Darwin's theory posits gradual accumulation of small changes drives species differentiation.
- The punctuated equilibrium debate questions whether macroevolutionary change is gradual or rapid.
- Distinguishing species evolution from fossil records is challenging.
Purpose of the Study:
- To investigate the relative contributions of gradual (anagenetic) and rapid (cladogenetic) evolution to species differentiation.
- To test Darwin's theory of gradual change against the punctuated equilibrium hypothesis using mammal body mass data.
Main Methods:
- Analysis of body masses for 2143 extant mammal species.
- Phylogenetic analysis incorporating nearly all 4510 extant mammal species.
- Bayesian estimation of evolutionary rates for gradual and speciational evolution.
Main Results:
- Gradual evolutionary processes account for a minor proportion of interspecific body size variation in mammals.
- Estimates from overall mammal data and specific clades (primates, carnivores) support this finding.
- Speciation events appear to be the primary drivers of significant body size differences between species.
Conclusions:
- Gradual microevolutionary change is not the primary driver of macroevolutionary divergence in mammal body size.
- The findings challenge the extent of gradualism in species evolution and lend support to models emphasizing rapid phenotypic shifts during speciation.
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