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Testing hypotheses of developmental constraints on mammalian brain partition evolution, using marsupials
Alison Carlisle1, Lynne Selwood2, Lyn A Hinds3
1The University of Queensland, School of Biological Sciences, St. Lucia, 4072 QLD, Australia.
Scientific Reports
|June 28, 2017
Summary
Mammalian brain partition evolution is driven by growth rate and duration differences, not just brain size. Early molecular programs may create developmental rigidity within species, influencing brain structure evolution.
Area of Science:
- Comparative neuroanatomy
- Evolutionary developmental biology
- Mammalian brain evolution
Background:
- Debate exists on whether mammalian brain partition volumes evolve due to functional selection or developmental constraints.
- Previous studies have not fully investigated developmental constraints on brain partition volume growth.
Purpose of the Study:
- To investigate developmental constraints on brain partition volume growth in marsupials.
- To determine if partition scaling with brain size is influenced by developmental factors or functional selection.
Main Methods:
- Contrast-enhanced micro-computed tomography (micro-CT) was used on hydrogel-stabilized marsupial brains.
- Analysis of partition vs. brain volume scaling using ANCOVAs.
- Comparison of growth curves between developing and adult marsupials across three species.
Main Results:
- Brain partition growth significantly differs between species and developmental stages (developing vs. adult).
- Partition growth appears independent of adult brain volume; differences arise from heterochrony (changes in growth rate/duration).
- Olfactory bulb growth scaling is irregular, suggesting fewer constraints, while other partitions show developmental rigidity.
Conclusions:
- Developmental constraints, specifically heterochrony, play a significant role in mammalian brain partition evolution.
- Phylogenetic signal in adult brain partitions counters expectations of development-mediated scaling conservatism.
- A rigid early molecular program may underlie species-specific developmental rigidity and influence neurogenesis-partition evolution links.
