Selection and the transferrin polymorphism in rhesus monkeys (Macaca mulatta)

Area of Science:

• Genetics and evolutionary biology
• Primate reproductive science

Background:

• The transferrin locus (TF) plays a role in iron metabolism and is known to be polymorphic in many species.
• Understanding genetic influences on primate survival, growth, and fertility is crucial for conservation and biomedical research.

Purpose of the Study:

• To investigate the association between transferrin C allele dosage and key life-history traits in rhesus monkeys.
• To explore the potential for balancing selection at the transferrin locus based on differential fitness components.

Main Methods:

• Comparison of survival, infant growth rates, and fertility metrics across rhesus monkeys with varying numbers of the C allele (0, 1, or 2) at the transferrin locus.
• Statistical analysis to determine significant differences in traits between genotype groups.

Main Results:

• Infants with no C allele (genotype 0) exhibited significantly slower growth rates compared to those with one or two C alleles.
• Heterozygous females (genotype 1) displayed the highest infant growth rates but concurrently showed reduced fertility, increased abortion rates, and higher stillbirth incidence.
• Females with two or no C alleles had comparatively lower infant growth rates but higher fertility and fewer pregnancy complications.

Conclusions:

• Opposing selective pressures on the transferrin locus across different life stages (infant growth vs. female fertility) may maintain genetic polymorphism.
• The transferrin locus appears to be under balancing selection in this rhesus monkey population, with heterozygote advantage for growth potentially offset by fitness costs in reproduction.