Conservation genetics molecular detectives at work
This topic is sponsored by the CRC for the Conservation and Management of Marsupials.
The new science of conservation genetics is providing important clues in the fight against the extinction of species.
|You will get more from this topic if you have mastered the basics of DNA and genes these links will take you to an annotated list of sites with helpful background information.|
Conservation geneticists take an understanding of genetics and evolution and apply it to conservation problems (Box 1: What is genetics?). They do so in two distinct ways. The first is largely concerned with genetic problems that may arise in small populations (Box 2: The problem of small populations). The second, which is the focus of this topic, uses genetic techniques to learn more about the history, biology and ecology of threatened species.
One of the principles of genetics is that the similarity between the DNA the basic genetic material of two individuals will depend on how closely related they are. The DNA of two baboons, for example, will be more similar than the DNA of a baboon and a chimpanzee. Conservation geneticists put this principle into practice in much of their work.
Conservation geneticists can be thought of as molecular detectives. They use tiny scraps of evidence to piece together events of the past. Recently, they employed their innovative techniques to solve the strange case of the missing tammar wallabies.
The intriguing case of the tammar wallaby
When colonial administrator Sir George Grey released a handful of tammar wallabies onto New Zealand’s Kawau Island in 1870, he may have inadvertently performed a great service for conservation. The species was once widespread in South Australia, but in the late 1800s the population on mainland Australia was in decline, a victim of habitat destruction, fox predation and shooting. By the early 1900s, it was extinct on the mainland.
Fortunately, the species itself wasn’t extinct. It still persisted on some islands, including Kangaroo Island. But these populations had been separated from the mainland population for around 10,000 years and were therefore likely to be quite different genetically. When the mainland population became extinct, the species lost a significant part of its genetic diversity.
Sir George didn’t record where he obtained his animals, but it was an important question. If they were from the Australian mainland, then their descendants were the last survivors of an otherwise extinct population, and were likely to be of considerable value for biodiversity conservation.
The only way to determine their origin was to compare their genetic make-up with that of the Kangaroo Island population, so this was what conservation biologists at the Cooperative Research Centre for Marsupial Conservation and Management did (Box 3: Molecular detectives at work). The evidence they uncovered was quite conclusive and great news for conservation. It showed that the Kawau Island colony had been established with animals from the mainland population. Land managers in South Australia are now considering plans to re-introduce the animals to their original range.
The many uses of conservation genetics
Genetic studies of plants and animals have several advantages. It often isn’t necessary to kill or even capture an organism to study it, since only small amounts of genetic material are needed. In studying the highly endangered northern hairy-nosed wombat, for example, researchers use samples of hair obtained from hair-traps located at the mouths of burrows. Genetic studies can also be carried out on tissue taken from dead organisms this has proved useful, for example, in identifying illegally harvested whale meat.
Conservation geneticists can also use genetic techniques to determine the amount of inter-breeding between different populations of the same species do populations intermingle, or are they cut off from each other by some kind of barrier? This is often of critical importance to conservation efforts. On the one hand, small, isolated populations with no ‘top-ups’ from other populations of the same species are more likely to become extinct; on the other hand, it may be desirable to keep certain populations separate to minimise genetic mixing and thereby maintain maximum diversity.
The potential of genetics as an aid to conservation is enormous and is only just starting to be realised. Yet, as conservation geneticists themselves point out, it cannot answer all the critical questions about species. Like any detective work, good ecological investigation requires information from a wide range of sources.
Related Nova topic
Australia's threatened species
Posted August 1999.