Using multilocus sequence data to assess population structure, natural selection, and linkage disequilibrium in wild...

Area of Science:

• Evolutionary genetics
• Population genetics
• Molecular evolution

Background:

• Understanding DNA polymorphism is key to studying evolutionary forces.
• Wild tomato species provide valuable models for genetic research.

Purpose of the Study:

• To investigate the impact of population subdivision and natural selection on DNA polymorphism in wild tomatoes.
• To compare nucleotide diversity and population structure in Solanum peruvianum and Solanum chilense.

Main Methods:

• Employed a multilocus approach using sequence data from 8 nuclear loci.
• Analyzed DNA polymorphism, population differentiation (FST), and demographic history (Tajima's D, Fu and Li's D).
• Assessed linkage disequilibrium (LD) decay with physical distance.

Main Results:

• Both wild tomato species show substantial nucleotide variation, with higher diversity in S. peruvianum.
• Evidence suggests an ongoing selective sweep at one locus in S. chilense.
• Population expansion, not just structure, explains excess low-frequency polymorphism.

Conclusions:

• Population structure and range expansion are crucial in shaping nucleotide diversity in wild tomatoes.
• High recombination rates and effective population sizes are indicated by rapid LD decay.
• The findings are promising for future association studies to map functional variation in wild tomatoes.