Accelerated Brain Shape Evolution Is Associated with Rapid Diversification in an Avian Radiation

Area of Science:

• Evolutionary Biology
• Paleontology
• Comparative Anatomy

Background:

• Niche expansion is crucial for speciation.
• Large brains are linked to cognitive abilities and niche expansion.
• The relationship between brain shape and macroevolutionary diversity is understudied.

Purpose of the Study:

• To develop a method for quantifying brain shape across species.
• To investigate evolutionary trends in brain shape within kingfishers (Alcedinidae).
• To correlate brain shape evolution with diversification rates and ecological factors.

Main Methods:

• A novel, semi-automated approach using X-ray microtomography and semilandmarks to phenotype brain shape.
• Multivariate comparative analyses of evolutionary trends.
• Examination of kingfisher (Aves: Alcedinidae) radiation.

Main Results:

• Rates of brain shape evolution positively correlate with lineage diversification rates.
• Beak shape evolution did not show this correlation.
• Specific brain shapes are associated with variations in body size and foraging behavior.

Conclusions:

• Brain shape evolution, constrained by allometry and ecology, may act as a master regulator of speciation.
• These findings support the role of the brain in processes like dispersal, foraging, and dietary niche.
• The developed method enables rapid phenotyping of brain shape for macroevolutionary studies.