VIP is developed for Spatial Vicariance Analysis. This method was based on the procedure proposed by Peter Hovenkamp. The main goal of Spatial Vicariance Analysis is to detect disjoint distributions among sister groups. Disjoint (vicariant, allopatric) distributions provide information about barriers that separate populations, and eventually lead to speciation.
For several reasons, allopatry among actual taxa is not always straightforward. VIP takes into account partial overlapping among distributions, as well as a heuristic detection of overlapping based on removal of distribution on some nodes. To make reconstructions comparable, an optimality criterion based on the number of vicariant nodes and the number of removed distributions is implemented in VIP.