Determining the species status of one of the world's rarest frogs: a conservation dilemma

New Zealand's native frogs (genus Leiopelma) are considered to be archaic a mphibians of exceptional scientific interest that appear to have remained v irtually unchanged for 160-200 million years. They are among the rarest ext ant amphibians and are highly restricted in distribution, confined to isola ted highly disjunct, populations on the North Island and a few small offsho re islands in Cook Strait. Previous investigations have suggested, based on patterns of allozyme variation, that the Stephens Island frog (Leiopelma h amiltoni) and Archey's frog (L. archeyi) are sister taxa to the exclusion o f the Maud Island frog, a species in close geographical proximity to the St ephens Island frog and previously viewed as a population of this species. A s a consequence of these data, a new species, L. pakeka, the Maud Island Fr og, has been described. This new species definition has dramatically enhanc ed the conservation status of L. hamiltoni, of which there are probably few er than 150 individuals. In this study we re-examine the systematics of the Leiopelmatidae using mtDNA sequence analyses. Partial 12 S ribosomal RNA a nd cytochrome b (Cyt b) gene sequences were obtained for 57 frogs from six populations representing all four extant Leiopelma species. Contrary to pre vious reports we find L. pakeka and L, hamiltoni to be monophyletic. The am ount of variation evident between these present species (<1% for Cyt b) is comparable to that seen between populations of L. archeyi. Based on these d ata, classification of L. pakeka and L. hamiltoni as separate species appea rs to be unwarranted, but they may be sufficiently distinct to warrant clas sification as evolutionarily significant units.