We provide a geographically well-sampled, time-calibrated molecular phylogeny for the Pacific monitor lizards
(Varanus: subgenus Euprepiosaurus) based on ND4 and 16S rRNA mitochondrial DNA sequences. Three well-
supported clades, or species groups, are retrieved: the Varanus doreanus Group, the V. jobiensis Group and the
V. indicus Group. The subgenus is estimated to have originated in the Mid-Miocene, but extant lineage diversification
dates from the Late Miocene and Pliocene. A rapid and widespread radiation of the V. indicus Group into the
South-West Pacific islands has occurred in the Pleistocene, but colonization onto these islands did not occur in a
linear, stepping-stone fashion. Genetically distinct populations – by tradition classified as V. indicus, but seemingly
representing distinct species – occur scattered on Tanimbar, several of the Solomon Islands, the Admiralty Islands,
the Louisiade Archipelago, Palau and Guam. Our analyses indicate that Varanus jobiensis is a species complex with
several divergent lineages that started to separate in the Pliocene and continued in the Pleistocene, the former
coinciding with the uplift of the Central Dividing Range on New Guinea. We find that sympatry among species of
Euprepiosaurus has not occurred until divergence times of 4.7–5.8 Myr have accrued.