Investigating the cause of the disjunct distribution of Amietophrynus pantherinus, the Endangered South African western leopard toad

More amphibians are threatened through loss of habitat than any other single factor. Conservation measures to restore habitat are dependent on historical data indicating the original extent of a species. When historical data is absent, disjunct distributions create a special problem for conservationists who need to determine whether they have an anthropogenic cause. The Endangered western leopard toad (Amietophrynus pantherinus) has a disjunct distribution in the south-western tip of South Africa. We use mitochondrial sequences from 153 individuals to show that the disjunct distribution is unlikely to have an anthropogenic origin. Two distinct populations are separated by 100 km, with highest probability for the most recent common ancestor arising some 5 Kya. The causes of this disjunct distribution appear to be too recent to be attributable to changes in sea level; instead we suggest that there was a range retraction associated with a distinct drying period in the area during the Holocene, possibly indicating that this species will be susceptible to future climate change. Further, we find that the eastern population is less genetically diverse and appears to be undergoing a serious reduction in range, despite its occurrence in the least urbanized habitat. Conservation measures suggested include surveys for breeding sites in the eastern population, custodian agreements for existing breeding sites and foraging areas and the need for a Biodiversity Management Plan to be drawn up and implemented.