Genomic Study of Australian Rock-Wallabies Reveals Complex Evolutionary History Through Museum Specimens

A scientific study has utilized DNA from historical and modern museum specimens to clarify the evolutionary relationships among four rock-wallaby species in northwestern Australia. Researchers from Macquarie University and the Australian Museum Research Institute, including Dr. Sally Potter and Dr. Mark Eldridge, analyzed genomic data to uncover historic gene flow between species despite significant differences in size, ecology, and chromosome numbers. The investigation focused on the brachyotis group of rock-wallabies, which includes the Monjon (Petrogale burbidgei), Nabarlek (Petrogale concinna), western short-eared rock-wallaby (Petrogale brachyotis), and Wilkins' rock-wallaby (Petrogale wilkinsi). These species inhabit the Kimberley and Top End regions of Australia's Monsoonal Tropics. Previous genetic studies using mitochondrial DNA had produced confusing patterns, suggesting populations of the same species were not closely related. The new research employed advanced genomic technologies to examine nearly a thousand genes from the nuclear genome, comparing them with mitochondrial DNA patterns. Analysis revealed that nuclear DNA resolved expected relationships based on morphology and chromosome numbers, while mitochondrial DNA showed different, more complex patterns. Unexpectedly, evidence indicated historic gene flow between species of varying sizes and ecologies, with mitochondrial DNA transferring between species populations. This discordance highlights that species boundaries are more permeable than previously thought and cautions against relying solely on mitochondrial DNA for species identification. The study underscores the fluid and complex nature of species boundaries, with genetic mixing occurring more frequently across space and time.