Evidence for Concerted and Mosaic Brain Evolution in Dragon Lizards

Area of Science:

• Neuroscience
• Evolutionary Biology
• Comparative Anatomy

Background:

• Brain evolution is shaped by selective pressures, leading to two main models: concerted brain evolution (coordinated changes) and mosaic brain evolution (independent changes).
• It remains unclear which factors favor concerted versus mosaic brain evolution.

Purpose of the Study:

• To investigate brain evolution in the agamid lizard genus Ctenophorus (dragons) by examining major neural subdivisions.
• To test whether concerted or mosaic brain evolution models are supported and how different selective drivers influence these patterns.

Main Methods:

• MRI was used to measure total and regional brain volumes in 14 species of Ctenophorus dragons.
• Species were assigned to ecomorphs based on habitat use and refuge type to analyze selection pressures.

Main Results:

• Evidence for both concerted and mosaic brain evolution was found in dragons.
• Concerted brain evolution was observed relative to body size, with all brain subdivisions increasing in volume.
• Mosaic brain evolution was detected relative to ecomorph, with the tectum and rhombencephalon showing opposite evolutionary patterns.

Conclusions:

• Both concerted and mosaic brain evolution occur simultaneously in dragons, influenced by specific selection drivers.
• The detection of concerted or mosaic brain evolution depends on the type of selection measured, not solely on the animal group studied.