Low nucleotide diversity in chimpanzees and bonobos.

Area of Science:

• Genetics
• Evolutionary Biology
• Primate Genomics

Background:

• Mitochondrial DNA (mtDNA) studies suggest chimpanzees have higher nucleotide diversity than humans.
• Previous limited data hinted at higher nuclear DNA diversity in chimpanzees as well.
• Understanding genetic diversity differences aids in reconstructing primate demographic history.

Purpose of the Study:

• To compare nucleotide diversity levels in the nuclear genomes of bonobos and chimpanzees with humans.
• To investigate the discrepancy between mitochondrial and nuclear DNA diversity estimates in humans and apes.
• To explore potential evolutionary mechanisms driving observed genetic diversity patterns.

Main Methods:

• Sequencing of 50 randomly selected noncoding, nonrepetitive nuclear DNA segments.
• Analysis of DNA samples from 9 bonobos and 17 chimpanzees.
• Calculation of nucleotide diversity (pi) values for different chimpanzee populations and bonobos.

Main Results:

• Bonobos exhibit lower nucleotide diversity (0.078%) than humans (0.088%) for the analyzed nuclear DNA segments.
• Chimpanzee nucleotide diversity (0.132% overall) is only slightly higher (up to 1.5 times) than human diversity.
• A significant disparity exists between high chimpanzee mtDNA diversity and lower nuclear DNA diversity compared to humans.

Conclusions:

• The previously assumed large difference in nuclear DNA diversity between humans and chimpanzees is not supported by this study.
• A reduction in effective population size (N(e)) in the human lineage post-divergence is a plausible explanation for the mtDNA/nuclear DNA diversity discrepancy.
• Further research is needed to fully elucidate the evolutionary forces shaping genetic diversity in hominoids.