The variance of pairwise nucleotide differences in two populations with migration

Area of Science:

• Population Genetics
• Molecular Evolution
• Bioinformatics

Background:

• Quantifying genetic divergence between populations is crucial for understanding evolutionary processes.
• Existing measures of genetic difference include average intrapopulation, interpopulation, and net nucleotide differences.
• These measures' expectations suggest utility in quantifying population divergence.

Purpose of the Study:

• Derive variances for three measures of pairwise genetic difference in populations with migration.
• Assess the reliability of these measures for quantifying population divergence.
• Compare variances under migration versus isolation to develop a demographic distinction test.

Main Methods:

• Mathematical derivation of variances for nucleotide difference measures under migration.
• Calculation of standard errors relative to expectations for these measures.
• Comparative analysis of derived variances with those from isolated populations.

Main Results:

• Expressions for the variances of three pairwise nucleotide difference measures were derived for migrating populations.
• Standard errors for these measures were found to be large relative to their expectations.
• Variances under migration were consistently greater than under isolation for all three measures.

Conclusions:

• The ability to quantify population divergence using these specific nucleotide difference measures is limited by large standard errors.
• The observed increase in variance under migration compared to isolation suggests a potential statistical test.
• Further research may refine methods for distinguishing demographic histories (migration vs. isolation) using genetic data.