Invasive species are considered one of the main drivers of the sixth mass extinction. Conservation solutions depend on whether a species is also indigenous to the country it invades (i.e., beyond its native range). In the case of invasive cryptic species, genetic tools are required to establish their identity. We illustrate these issues with the human-mediated colonization of the Dutch coastal dunes by Hyla tree frogs. Although previously assumed to concern the indigenous common tree frog H. arborea , European tree frogs comprise a complex of allopatric cryptic species, meaning the taxonomic identity of introduced Dutch populations warrants investigation. We sequence mtDNA for 164 individuals from native and introduced populations across the Netherlands and compare our dataset with hundreds of Hyla haplotypes previously barcoded in the Western Palearctic. Two of the dune populations carry an mtDNA haplotype of the native species H. arborea that occurs naturally elsewhere in the Netherlands. In contrast, ...