  Recently, the selection-recombination equation with a single selected site
and an arbitrary number of neutral sites was solved by means of the ancestral
selection-recombination graph. Here, we introduce a more accessible approach,
namely the ancestral initiation graph. The construction is based on a
discretisation of the selection-recombination equation. We apply our method to
systematically explain a long-standing observation concerning the dynamics of
linkage disequilibrium between two neutral loci hitchhiking along with a
selected one. In particular, this clarifies the nontrivial dependence on the
position of the selected site.
