Phylogeny and taxonomy of the Pacific monitor lizards (Squamata: Varanus: Euprepiosaurus)

The monitor lizards of the subgenus Euprepiosaurus Fitzinger, popularly known as the Pacific monitor lizards, are widely distributed on islands in the southwest Pacific region where they often form conspicuous components of the local faunal communities. Despite their notable size, importance as top predators, and the widespread use of their meat and skins by local communities, the number of species, phylogenetic relationships, and distribution of these lizards have remained poorly known. Most species have been described recently and known to science only from colonial-era museum collections or from animals reaching Europe through the international pet trade. The number of recognized species has risen from two to fourteen since 1990, both as a result of revisions of populations previously assigned to Varanus indicus, and from the discovery of completely new species. This dissertation investigates the phylogenetic relationships and taxonomy of Euprepiosaurus throughout its extensive geographical range. It relies on a combination of molecular, morphological, and field data to reveal species boundaries and species distributions. Tissue samples were collected over twelve months of fieldwork in the Papua New Guinean island provinces, and sampled from existing museum collections. The results are presented in four separate chapters (one manuscript and three published articles). The first chapter is the most well-sampled molecular phylogeny of the subgenus Euprepiosaurus and Hapterosaurus Bucklitsch to date. It includes 96 samples representing 14 recognized species and several apparently new species. Two mitochondrial genes (ND4 and 16S) were sequenced and Maximum Likelihood, Parsimony and Bayesian inference approaches were used for phylogenetic reconstructions. BEAST was used to estimate lineage divergence times. All analyses retreive both Euprepiosaurus and Hapterosaurus as monophyletic. Within Euprepiosaurus three clades, or species-groups, are recovered as monophyletic with varying support. These are the V. doreanus group, the V. indicus group, and the V. jobiensis group (currently consisting of a single species). The V. doreanus group consist of four recognized species – all of which are well-supported and monophyletic in our analysis. Varanus doreanus which is geographically widespread on New Guinea, Cape York, Aru and other satellite islands positions as a sister taxon to a clade containing the single-island endemics V. finschi, V. semotus and V. yuwonoi. The V. indicus group is estimated to have radiated rapidly during the Pleistocene, resulting in a number of allopatric island endemics. Varanus indicus is the most widespread species and occurs throughout New Guinea and its offshore islands, New Britain, Cape York and parts of the Northern Territory. Other well supported monophyletic lineages include V. cerambonensis, V. melinus, V. douarrha, and several apparently new species from insular PNG, the Solomon Islands, Western Micronesia, and the Moluccas. The Varanus jobiensis specimens included in this study are resolved as a well-supported monophyletic clade consisting of several divergent lineages. The populations from the western and eastern part of the range are estimated to have diverged 3-7 million years ago, suggesting that V. jobiensis may represent a species complex.