Over 40 years in the making: the two new subspecies of Rock-wallabies
Although commonly seen by tourists around Alice Springs, the Rock-wallabies of Central Australia have lacked an appropriate scientific name … until now.
The Black-footed Rock-wallaby, Petrogale lateralis, is the most widespread and sporadically distributed rock-wallaby species in Australia. Considerable morphological and genetic differences within this species have long been known, with three named subspecies and two unnamed forms recognised. After 40 years of research, we are now able to formally name the central Australian and West Kimberley populations of P. lateralis as new subspecies.
The warru or Central Australian rock-wallaby Petrogale lateralis centralis has been newly recognized as a morphologically and genetically distinct subspecies.
Image: Mark Eldridge© Australian Museum
With at least 17 species, rock-wallabies are one of the most evolutionarily successful groups of mammals in Australia. Their relatively recent and rapid diversification within Australia, associated with variable amounts of morphological change, has presented scientists with many challenges in trying to identify the different species and understand their evolutionary history and inter-relationships. After more than 40 years of research, considerable progress has been made in understanding rock-wallaby taxonomy, with five new species/subspecies described and other species divided up or combined.
But some challenges still remain: the presence of considerable variation within the Black-footed Rock-wallaby being one of them. With a patchy distribution that stretches from temperate southern Western Australia (WA) and South Australia (SA), through the arid central Australian deserts, north west to the edge of the monsoon tropics in the Kimberley, it is unsurprising that the Black-footed Rock-wallaby shows considerable regional variation. In the 1970s, the pioneering work of Professor Geoff Sharman and his colleagues from Macquarie University identified five regionally distinct chromosome races within the Black-footed Rock-wallaby across its range. Historically, this pattern of variation was summarised taxonomically in three described subspecies and two undescribed forms. Subsequently, morphological and genetic studies over the past four decades have demonstrated that these five subspecies/races are closely related but distinguishable. They also appear able to interbreed and freely exchange genes, indicating they are members of a single variable biological species.
Dr Mark Eldridge studying specimens in the mammal collection, Australian Museum Research Institute. Scientists study specimens in museums such as these to help identify new species and subspecies.
Image: Stuart Humphreys© Australian Museum
Ironically, the widespread but unnamed arid-adapted population from the ranges of central Australia, known locally as Warru, is genetically the most distinct and is estimated to have diverged from the other populations over 1 million years ago. Similarly, the population with the most distinctive external morphology is the pale and yellowish unnamed population confined to a small area of the West Kimberley, where it is known locally as Wiliji. Since both of these unique populations are distinct forms of the Black-footed Rock-wallaby, and in order to achieve greater taxonomic consistency and stability, we have formally named them as new subspecies of Petrogale lateralis.
Both these newly named subspecies (Petrogale lateralis centralis and Petrogale lateralis kimberleyensis) are threatened and have declined through parts of their range with some local populations becoming extinct. It is hoped that our improved understanding of the diversity within Black-footed Rock-wallabies will aid their conservation and management.
Dr Mark Eldridge, Principal Research Scientist, Australian Museum Research Institute.
Dr Sally Potter, Research Associate, Australian Museum Research Institute; Postdoctoral Fellow, Australian National University.
More information:
Eldridge, M.D.B. and Potter, S. 2020. Taxonomy of rock-wallabies, Petrogale (Marsupialia: Macropodidae). V. A description of two new subspecies of the black-footed rock-wallaby (Petrogale lateralis). Australian Journal of Zoology https://doi.org/10.1071/ZO19063
Potter, S., Cooper, S. J. B., Metcalfe, C. J., Taggart, D. A., and Eldridge, M. D. B. (2012). Phylogenetic relationships within Petrogale (Marsupialia: Macropodidae) and their biogeographic history within Australia. Molecular Phylogenetics and Evolution 62, 640–652. https://doi.org/10.1016/j.ympev.2011.11.005
