Bulletin

Issue: March 2005

Research in Action

Genetic time machine helps plan forests of the future

Success often comes from 90 per cent perspiration and 10 per cent inspiration.

La Trobe University geneticists are using a genetic ‘time machine’ – which takes them back millions of years – to help them make recommendations for the future health of our forests.
Their ‘time machine’ enables them to pinpoint Noah’s Ark-type refuges where tiny forest creatures have taken refuge and safeguarded their unique DNA structures during successive ice ages.

They have located a number of these refuges high in the Great Dividing Range in the Tallaganda State Forest and National Park about 80 km south east of Canberra.

The same refuges have been used during all the ice ages that have occurred at 100,000 year intervals over about the past two million years. The log-dwelling invertebrates dubbed ‘giant’ Collembola move away from the refuges when the ice ages end – but retreat back to them when the next one approaches and causes downhill contraction of the forests on which the animals depend.

Their presence today is vital, owing to their role in the ecological community that keeps forests healthy by breaking down forest floor litter and rotting logs, thereby enriching the soil. Should their special refuge habitats be destroyed by logging or other means, their role in maintaining future forest health and biodiversity will disappear. La Trobe PhD student,
Mr Ryan Garrick, is making a significant contribution to this overall study by researching the phylogeography, the relationship between gene relationships and geography, of giant Collembola.

A paper on his work appeared in the November 2004 edition of the science journal, Molecular Ecology.

The 6 mm-long log-dwelling six-legged invertebrates are called giant Collembola to distinguish them from the common microscopic Collembola which exist in countless millions in leaf litter and soil.

Like their tiny but abundant cousins, commonly known as springtails, giant Collembola are primitive insects. Unlike their relatives, giant Collembola are little-known, are specially adapted to living in rotting logs, and have no ‘spring’. They play an important role in the ‘saproxylic’ – decomposing wood – habitat. Primarily they eat slime moulds and small fungi which invade rotting logs.

Delineation of the glacial refuges became possible only with the recent application of genetic ‘time machine’ techniques by which the geneticists examine evolutionary relationships among different mitochondrial DNA sequences from Collembola found in different parts of the 100 kilometre long forest.

Mr Garrick located the refuges that comprise deep gullies and creeks high in the mountains likely to have retained some forest coverage during succeeding ice ages.

He found that each Collembolon living inside a particular refuge contained similar DNA, but there were strong genetic differences among Collembola collected in adjoining refuges, some of which are less than 15 kilometres apart. Such large genetic differences occurring over very small spatial scales have seldom been reported, but may well be a common phenomenon for log-dwelling invertebrates.

‘It remains to be confirmed, but at the moment we think that some of these different Collembola do not interbreed when they venture from the refuges at the end of each ice age,’ Mr Garrick said.

‘The technology enables us to detect major changes, for example, what major splits occurred in animals that lived in different parts of the forest,’ he said.

Apart from publication in Molecular Ecology, Mr Garrick has received additional recognition for his work.

He won the La Trobe University David Myers PhD Scholarship and in 2003 was awarded a two-year research grant by the ANZ Trustees, Holsworth Wildlife Research Fund. He was also sponsored to attend the International Congress of Genetics (Genetics Society of Australia) and 34th Australian Entomological Society/ 6th Invertebrate Biodiversity & Conservation Conference (Department of the Environment and Heritage).

His PhD supervisor, La Trobe senior lecturer in Genetics, Dr Paul Sunnucks, said Mr Garrick’s research was making a significant contribution towards the future management of the State Forest and National Park area.

‘Some parts of the State Forest have been logged over the past century, are being logged and can potentially be logged in future. Some areas must be protected – such as those refuges where biodiversity is generated and maintained,’ Dr Sunnucks said.

‘Ryan’s work will allow prioritisation and thus protection of evolutionarily important parts of the forest. This will achieve the maintenance not only of the pattern of biodiversity, but also the fundamental processes generating it.’