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Evolutionary divergence in brain size between migratory and resident birds
Daniel Sol1, Núria Garcia, Andrew Iwaniuk
1Centre for Ecological Research and Applied Forestries, Autonomous University of Barcelona, Bellaterra, Catalonia, Spain. d.sol@creaf.uab.es
Plos One
|March 13, 2010
Summary
Migratory birds, particularly passerines, have smaller brains relative to body size than resident species. This suggests migration may select for reduced brain size due to energetic and cognitive costs.
Area of Science:
- Evolutionary biology
- Neuroscience
- Ornithology
Background:
- Brain size evolution in birds is complex and debated.
- Passerine birds exhibit significant diversity in brain size.
- Previous studies suggested a link between migration and brain size, but this is generalized here.
Purpose of the Study:
- To investigate the evolutionary pressures driving brain size diversification in passerine birds.
- To determine the relationship between migratory behavior and relative brain size.
- To explore the selective forces favoring smaller brains in migratory species.
Main Methods:
- Comparative analysis of brain size relative to body size in migratory and resident passerine species.
- Phylogenetic reconstructions using Bayesian Markov chain methods.
- Path analysis to disentangle direct and indirect effects of migration on brain size.
Main Results:
- Migratory passerine species possess significantly smaller brains relative to body size compared to resident species.
- Phylogenetic analyses suggest migration evolved in large-brained tropical species, subsequently selecting for smaller brains.
- Over 68% of the correlation between brain mass and migratory distance is directly attributable to migration's effect on brain size.
Conclusions:
- Migration is a significant selective pressure that can lead to reduced brain size in birds.
- The energetic and cognitive costs associated with migration may drive selection for smaller brains.
- Brain evolution is shaped by diverse selective pressures, and larger brain size is not universally advantageous.
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