The Australian dragon lizard genus Diporiphora currently comprises 21 species based on genetic and morphological evidence, with 11 of these species occurring in the monsoonal tropics of northern Australia. Diporiphora are climbing lizards that are found on either trees, grasses or rocks, with usually only subtle morphological differences to distinguish between species. Since the last taxonomic treatment of this genus in northern Australia over 40 years ago, species delimitation using genetic techniques has clarified the number of lineages and increased collections from recent surveys have significantly broadened the distributions of these taxa. However, no formal taxonomic assessments have been undertaken to redefine species, including the many lineages that represent undescribed species. Currently, there are seven species of Diporiphora with vast distributions across northern Australia and a broad and variable set of morphological characteristics that make species identification challenging, even for experienced field workers. Here, we provide a comprehensive taxonomic treatment of Diporiphora species across northern Australia based on previously published genetic data and morphological examination of voucher specimens. Our analyses demonstrate that these broadly distributed taxa actually comprise multiple, often allopatric, species, with especially high diversity in the Kimberley region of Western Australia. We redescribe nine previously described species and describe five new species of Diporiphora based on historical types, newly collected material and older museum vouchers. In the D. australis species group, we resurrect D. jugularis Macleay from synonomy. In the D. bennettii species group, we synonomise D. arnhemica Storr with D. albilabris Storr, and raise to full species the latter and D. sobria Storr. In addition, we describe as new a wide-ranging saxicoline species previously attributed to D. bennettii Gray. In the D. bilineata species group, we resurrect D. margaretae Storr from synonomy with D. magna Storr and describe three new species. Lastly, we describe a species from the northwest Kimberley that is more closely related to an arid zone radiation. The revision of the northern Diporiphora dragons here stabilises the taxonomy, redefines many species distributions and reveals many new species. Further work on Diporiphora includes further surveys to better understand distributions and habitat preferences and continue to refine their evolutionary history and biogeography in northern Australia.

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Human-mediated dispersal of animals often acts to bring populations that have been separated for substantial periods of evolutionary time (e.g. millions of years) in their native range into contact in their introduced range. Whether these taxa successfully interbreed in the introduced range provides information on the strength of reproductive isolation amongst them. The invasive delicate skink (Lampropholis delicata) has been accidentally introduced to Lord Howe Island from four genetically divergent (>2 million years) regions of the species’ native range in eastern Australia. We used mitochondrial DNA and microsatellite data to investigate whether the individuals from four of the native-range source regions are interbreeding on Lord Howe Island. Our analyses indicate that intraspecific hybridisation among individuals from all four native-range source regions is occurring. Although there is little evidence for hybrids in the northern end of Lord Howe Island (proportion of hybrids: 0–0.02; n = 31), there is a high proportion of hybrids in the central (0.33–0.69; n = 59) and southern regions (0.38–0.75; n = 8) of the island. Given the strong evidence for interbreeding among all four native-range source regions examined, and the relatively minor morphological, life-history and phenotypic variation among them, we suggest that the delicate skink should continue to be treated as a single, widespread, but variable species.