The homeless earless dragon?
Posted 9th December 2016
The grassland earless dragon (Tympanocyrptis pinguicolla) is a small and feisty lizard. If only it was more like its ‘dragon’ namesake perhaps the battle to preserve habitat would be successful. As it stands, the earless dragon has suffered a large decline in population size and range due to development of its grassland habitat. Once found in large numbers across the landscape, this reptile is currently restricted to just three small areas. Scientists at the IAE are studying their genetics to provide evidence that will help in the conservation effort of the species. We talk to Dr Anna MacDonald about their work.
Previous studies show the populations in Canberra and the Monaro region have diverged genetically. What did your study find?
We used a different type of genetic marker known as “microsatellites” to characterise the genetic profiles of a couple of hundred dragons. Like the previous study, we found a clear genetic distinction between animals from Canberra and animals from the Monaro region, but in addition we identified genetic differences between animals from the north and south of Canberra, where lizard populations are separated by the Molonglo River. So, overall we have identified three distinct genetic clusters of earless dragons.
Is it important to consider them as separate species for conservation efforts?
It is definitely important to consider the conservation needs of each genetic unit. However, whether we should now think of them as one, two or three different species is a much more difficult question. To formally describe each cluster as a separate species would require a lot more evidence than we have at the moment, and we may go through a lengthy process to collect evidence only to find that species boundaries remain uncertain. In the meantime, the dragons may have edged a little closer to extinction. Fortunately the Environment Protection and Biodiversity Conservation Act allows for a biological entity, such as a sub-species or a putative new species, to be classed as a “species” for conservation purposes. This is important as animals from different genetic lineages may have developed slightly different adaptations to their local environments. If we were to manage all of the grassland earless dragons as one entity we might lose this evolutionary potential.
Captive breeding is a valuable tool for wildlife conservation, and the University of Canberra has set up a captive breeding colony for the grassland earless dragon. We need to balance the risks of breeding animals from different genetic units (and potentially different species) with the risks of inbreeding in very small populations (where introducing new genetic material could be a good thing). Fortunately, we now have a better understanding of genetic diversity within the remaining grassland earless dragon populations, which will help us to manage the captive breeding colony.
What is the current population status of the earless dragon?
Both Canberra populations are seriously affected by habitat fragmentation. They live in areas with high densities of roads, buildings, and even near the airport. University of Canberra researchers recorded dramatic population collapses at some Canberra sites during the millennium drought, and we have concerns that some populations are now too fragmented to allow the animals to disperse naturally between sites. It isn’t easy for a little grassland lizard to cross a big road or to find its way through a suburb. This not only puts isolated populations at risk of inbreeding, but also affects the ability of the species to recolonise if an area is affected by an extreme event, such as fire or flood.
Are you optimistic for the survival of the earless dragon?
I am cautiously optimistic. I say cautiously because the future of the earless dragon is reliant on our ability to preserve suitable habitat. This is particularly relevant in Canberra’s north and in the Monaro region, where very little of their known habitat is protected by reserves or parks. If we can maintain enough habitat and connectivity between populations to protect the dragon against future challenges, such as droughts and climate change, then yes. But we shouldn’t be complacent.
Photo credit: Anna MacDonald