Genetic variation in baboon craniofacial sexual dimorphism

Area of Science:

• Evolutionary biology
• Genetics
• Primatology

Background:

• Sexual dimorphism is a key driver of intraspecies variation, yet its genetic underpinnings for complex traits remain largely elusive.
• Cranial traits in highly dimorphic species offer a model to explore sex-specific genetic architectures and evolutionary mechanisms.
• Baboons (Papio) exhibit significant cranial sexual dimorphism, making them ideal subjects for genetic analysis.

Purpose of the Study:

• To investigate the genetic basis of cranial sexual dimorphism in baboons.
• To identify gene-by-sex (G x S) interactions and X-linked heritability in cranial traits.
• To test the hypothesis that highly dimorphic facial traits show stronger G x S or X-linked effects.

Main Methods:

• Utilized 3D landmark data from CT scans of 402 baboon skulls with known genealogy.
• Estimated genetic variance parameters separately for males and females.
• Analyzed gene-by-sex interactions and X-linked heritability for cranial measurements.

Main Results:

• Gene-by-sex (G x S) interactions and X-linked effects were detected for cranial measures linking the face to the neurocranium.
• No significant G x S interactions or X-linked effects were found for traits exclusively within the face.
• Facial traits in this baboon population showed limited genetic basis for further dimorphic evolution.

Conclusions:

• The genetic architecture of cranial traits, particularly facial ones, may constrain the evolutionary trajectory of sexual dimorphism in baboons.
• Understanding G x S interactions and X-linked effects is crucial for predicting the evolutionary potential of dimorphic traits.
• This study provides insights into the genetic origins and future evolution of cranial sexual dimorphism in primates.