Biogeography of New Zealand lizards

New Zealand has a diverse lizard fauna, comprising diplodactylid geckos and skinks and over 100 recognised species or taxa. Geckos are thought to have colonised New Zealand during the Eocene or Oligocene (40.2–24.4 mya), prior to the ‘Oligocene drowning’ event. In contrast, skinks reached New Zealand during the Miocene (~18.3 mya) via long-distance overwater dispersal from New Caledonia along the Lord Howe Rise and Norfolk Ridge. Investigations of the biogeography of New Zealand lizards have long been hampered by two key factors: recent range contractions and local extinctions following the successful establishment of 31 exotic mammalian species and taxonomic gaps and a limited grasp on the true diversity of the endemic lizard fauna. However, subfossil records have improved our understanding of the prehuman distributions of several previously widespread species, and intensive taxonomic activity over the last two decades has provided a more accurate estimate of lizard diversity. This enhanced knowledge has enabled the key historical processes responsible for the diversification of lizards within New Zealand to be identified. These include sea-level changes during the Pliocene–Pleistocene in northern New Zealand, the Pliocene marine inundation of the lower North Island, the impact of water barriers such as Cook Strait (separating the North and South Islands) and Foveaux Strait (separating the South Island and Stewart island), tectonic activity along the Alpine Fault and regional north–south differentiation within the South Island. We provide an updated list of 22 biogeographic categories for New Zealand lizards. We highlight that the essential framework is now in place with which to investigate the biogeographic patterns evident in the New Zealand lizard fauna and examine the processes that have created them.