Diet, bite force and skull morphology in the generalist rodent morphotype

Area of Science:

• Ecology
• Evolutionary Biology
• Biomechanics

Background:

• Bite force is crucial for vertebrate function and linked to ecological niche, particularly diet.
• A proposed trade-off exists between rodents specialized for gnawing (seeds) and chewing (vegetation).

Purpose of the Study:

• To test the hypothesis that gnawers possess stronger bite forces than chewers.
• To investigate the causal relationships between diet, bite force, and craniodental morphology in myomorph sigmodontines.

Main Methods:

• Bite force estimation and measurement of skull and mandible shape/size in 63 sigmodontine genera.
• Comparative analysis of diet's influence on bite force and morphology.
• Phylogenetic path analysis to determine causal links between diet and bite force.

Main Results:

• Granivores (gnawers) and herbivores (chewers) exhibited similar, high bite forces, refuting the initial hypothesis.
• Phylogenetic path analysis indicated diet influences bite force, rather than the reverse.
• Sigmodontine rodents, regardless of diet, display intermediate phenotypes compared to extreme gnawers or chewers.

Conclusions:

• The absence of a bite force trade-off in sigmodontine rodents may stem from their generalist nature.
• Natural selection modifies bite force through craniodental morphology adjustments in response to dietary shifts.
• Insectivorous rodents show distinct morphological adaptations, suggesting a different evolutionary trajectory.