Functional constraints channel mandible shape ontogenies in rodents

Area of Science:

• Developmental biology
• Evolutionary biology
• Comparative anatomy

Background:

• Postnatal growth is crucial for mammalian adult shape, with the mandible undergoing significant changes.
• Functional constraints from diet and behavior influence mandibular bone remodeling and shape acquisition.
• Interactions between bone, muscles, and teeth drive developmental plasticity, impacting ontogeny and evolution.

Purpose of the Study:

• To investigate the role of tissue interactions in shaping mandibular ontogenetic trajectories.
• To compare mandible shape development across different postnatal stages in three rodent species.
• To understand how functional constraints influence developmental convergence.

Main Methods:

• Geometric morphometrics was used to analyze mandible shape.
• Comparative analysis was performed on five postnatal stages in Mus musculus (house mouse), Meriones unguiculatus (Mongolian gerbil), and Mesocricetus auratus (golden hamster).

Main Results:

• Early mandible shape differentiation was observed, with gerbils and hamsters showing distinct patterns compared to mice.
• Ontogenetic trajectories became more similar around the weaning stage across the three species.
• This convergence is attributed to similar physical constraints imposed by dietary and behavioral changes at weaning.

Conclusions:

• Functional constraints, particularly muscle loading around weaning, drive convergence in mandibular ontogeny.
• Despite early anatomical divergence, similar environmental pressures can lead to similar developmental pathways.
• Rodent mandible development illustrates the interplay between genetic predisposition and environmental influences on evolutionary trajectories.