Oliver, Paul MRittmeyer, EricTorkkola, JanneDonnellan, Stephen C.Dahl, ChrisRichards, Stephen J.2022-11-022022-11-020004-959Xhttp://hdl.handle.net/1885/277965Australia and New Guinea (together referred to as Sahul) were linked by land for much of the late Tertiary and share many biotic elements. However, New Guinea is dominated by rainforest, and northern Australia by savannah. Resolving patterns of biotic interchange between these two regions is critical to understanding the expansion and contraction of both habitat types. The green tree frog (Litoria caerulea) has a vast range across northern and eastern Australia and New Guinea. An assessment of mitochondrial and morphological diversity in this nominal taxon in New Guinea reveals two taxa. True Litoria caerulea occurs in disjunct savannahs of the Trans-Fly, Central Province and across northern Australia, with very low genetic divergence, implying late Pleistocene connectivity. A previously unrecognised taxon is endemic to New Guinea and widespread in lowland swampy rainforest. Date estimates for the divergence of the new species suggest Pliocene connectivity across lowland tropical habitats of northern Australia and New Guinea. In contrast, the new species shows shallow phylogeographic structuring across the central mountains of New Guinea, implying recent dispersal between the northern and southern lowlands. These results emphasise that the extent and connectivity of lowland rainforest and savannah environments across northern Australia and southern New Guinea have undergone profound shifts since the late Pliocene.Fieldwork in Papua New Guinea was supported by Total E&P PNG Limited, ExxonMobil PNG Limited (EMPNG), and Conservation International. We also thank the Papua New Guinea National Research Institute (NRI) and the Papua New Guinea Conservation and Environment Protection Authority (CEPA) for providing relevant visas, research approvals and export permissions. SJR is particularly grateful to Barnabas Wilmott (CEPA) and Georgia Kaipu (NRI) for their assistance. We thank Mark Hutchinson, Carolyn Kovach, Jodi Rowley, Patrick Couper and Andrew Amey for providing access to specimens in their care. CD was partially supported by grants to Vojtech Novotny from the Czech Ministry of Education (CZ.1.07/2.3.00/20.0064, LH11008), the UK Darwin Initiative, and the US National Science Foundation (DEB0211591), and is also grateful to the Wildlife Conservation Society (PNG) and the New Guinea Binatang Research Center for their support. ER was supported by grants from the National Science Foundation (DEB 1402285). PMO was supported by grants from the Australian Research Council, and genetic data collection was supported by a grant from the Australian Biological Resources Survey to SDapplication/pdfen-AU© CSIRO 2020 Open Access CC BY-NChttps://creativecommons.org/licenses/by-nc/4.0/Australian Monsoonal Tropicsbiotic exchangeLitoria caeruleaLitoria mira sp. nov.New GuinearainforestSahulsavannahTrans-Flytree frogMultiple trans-Torres Strait colonisations by tree frogs in the Litoria caerulea group, with the description of a new species from New Guinea202010.1071/ZO200712021-11-28CC BY-NC