Enter your Effective Population Size (Ne), Sample Size (n), Mutation Rate (μ), Generation Time, and Ploidy into the Coalescence Time Calculator to find the Expected Coalescence Time in generations and years, plus the Population Mutation Parameter (θ) and Watterson's Estimator for your lineage.
Expected Coalescence Time
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Coalescence Time in Years
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Population Mutation Parameter (θ)
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Watterson's Estimator
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Coalescence time is the expected number of generations back to the most recent common ancestor (MRCA) of a sample of alleles. It represents how long ago all sampled alleles shared a common ancestral copy.
Larger effective population sizes lead to longer coalescence times. In larger populations, it takes more generations for lineages to coalesce because there are more potential ancestors at each generation going backward in time.
Mutation rate affects the population mutation parameter θ = 4Neμ (for diploids). Higher mutation rates increase genetic diversity and can be used to estimate coalescence times from observed sequence variation.
Sample size determines how many lineages we're tracing back in time. Larger samples generally have more recent common ancestors because more lineages increase the probability of recent coalescence events.
Watterson's estimator is a method to estimate the population mutation parameter θ from the number of segregating sites in a DNA sequence sample. It's based on the expected number of mutations in the genealogy.
Ploidy affects the effective number of gene copies in a population. Diploid organisms have twice as many gene copies as haploids, which influences the coalescence rate and population genetic parameters.
This calculator provides general coalescence estimates but assumes random mating and neutral evolution. Results should be interpreted carefully for species with complex mating systems, population structure, or strong selection.