2010 ZAA (ARAZPA) Research Award

Conservation Ark has recently won another award for research into wildlife and conservation.

Research carried out by Conservation Ark and their partners on Short-eared rock-wallabies in the Kimberley region of WA, has won the 2010 Zoo Aquarium Association Research Award.

Conservation Ark staff have been working in the Kimberleys since 2006. In 2007, Sally Potter started her PhD, supervised by David Taggart, to look at the genetics of the rock-wallabies in this area (for more information about this project click here). This project has uncovered interesting information that will have important implications for the conservation management of rock-wallabies.

Northern Australia faces numerous environmental pressures including changes in fire regimes, mining and climate change. The magnitude of these impacts is already evident with many species being restricted in range and requiring revisions of their conservation status.

This project looked into the population dynamics of the short-eared rock-wallaby, to provide a framework for understanding the ecology of the monsoon tropics in a restricted dispersal species. This study helps work out the evolution of biogeographical processes in this region and provides valuable information on speciation and evolutionary significant units within these species. This information is necessary in order to optimize future management and conservation initiatives.

The brachyotis group of rock-wallabies contains the monjon, the nabarlek and the short-eared rock wallaby. These are the least understood of the 16 rock-wallaby species in Australia, in terms of their ecology and population biology.

A recent study looked at the relatedness of short-eared rock-wallaby colonies in the Northern Territory and discovered exceptionally high levels of sequence divergence in mitochondrial DNA (mtDNA) within populations. These findings question both taxonomic classifications and the causes for such diversification within the species. Further sampling from across their range was designed to help clarify current taxonomic classifications, determine the presence of evolutionary significant management units across their distribution, and provide evidence of their evolutionary history. 

Given the lack of knowledge on the Kimberley Short-eared rock-wallaby, this part of the project aimed to:

• Investigate the phylogeography and population genetics of the short-eared rock-wallaby
  • To determine the level of genetic diversity and establish a relationship between spatial patterns and genetic variation across the landscape;
  • To investigate whether the widespread and morphologically variable short-eared rock-wallaby is a single species or actually comprises multiple species/sub-species;
  • To determine gene flow and dispersal patterns amongst populations throughout their range and in particular the Kimberley; 
• To determine the conservation management priorities for the short-eared rock-wallaby across its range

Mitochondrial DNA analysis indicates that the short-eared rock-wallaby is probably more than one species, with multiple geographical barriers appearing across the landscape. Significant variation in mtDNA between populations from the Northern Territory compared to the Kimberley and further subdivision within the Kimberley have been identified. These results need to be confirmed with comparable nuclear DNA analysis and standard morphological assessment. A strong isolation by distance relationship has been observed for mtDNA, which indicates that females within this species are highly philopatric, resulting in restricted gene flow amongst populations, especially at greater distances. 

The variation in mtDNA between the short-eared rock-wallaby populations from the NT and the Kimberley is greater than that found between short-eared rock wallaby populations from the Kimberley and the monjon, a completely different species. This indicates long term isolation between the NT and WA populations of short-eared rock wallabies. The biogeographic patterns emerging within the short-eared rock-wallaby appear to be associated with major breaks in the sandstone structures across their range. A physical barrier located along the Daly River, referred to as the Victoria River Drainage barrier, has been identified previously for bird species (Ford 1978).  Similar patterns are also emerging from studies of rodent records.

The results suggest that a revision to the short-eared rock-wallaby taxonomic classification is necessary, with a detailed morphological assessment. These results indicate at least two species (NT & WA) currently referred to as ‘the short-eared rock wallaby’, with nuclear sequence data supporting the split between populations in NT and WA. Further analysis is required to determine what patterns will emerge within the Kimberley and Victoria River (NT) regions.

Microsatellite markers have also been used in this study to assess the dispersal patterns of the short-eared rock-wallaby at a finer scale, but further analysis of the genotypes of these loci is required. Extraction of DNA from scat samples together with genomic DNA was utilised to assess the fine scale population structure.

The findings highlight that any future conservation plans must, at a minimum, recognise the diversity between populations in the NT and WA. This would mean that management implications would need to focus within these two regions separately. The significance of these biogeographical barriers is emerging in other species as well, and further comparative studies will highlight evolutionary historical events that may have lead to the diversification of the organisms in this region. This study also highlights the importance of focusing on specific bioregions within northern Australia. Climatic and geological events have resulted in the formation of barriers within and between these organisms and have shaped their current distributions and diversity. A lot can be learnt from understanding these biogeographic patterns and utilising the information in future efforts to conserve these and other species.