Figure 1.

An ancestral recombination graph (ARG) at two loci, labeled “a” and “b”, each with two alleles ($\mathrm{•}$ and $\circ$). The notations $n,n_{ij},n^{\left(abc\right)}$ are illustrated for the configuration between the first coalescence and second recombination event. The symbol $\mathrm{\ast }$ denotes a missing allele.