Silvertop Study Reveals Healthy Genetics

Article excerpt

For scientists studying population genetics, challenges lie not only in the laboratory, where they tangle with DNA, but also in the field, where the task of gathering genetic resources can be equally demanding.

Innovative techniques are often needed to collect DNA from native mammals. Northern hairy-nosed wombats in Queensland's Epping Forest National Park -- which hate to be trapped -- are cleverly monitored by collecting hairs on sticky tapes laid across burrow entrances. Enough genetic information is contained in the hair follicles to enable their individual identification.

Despite their relative immobility, members of the Plant Kingdom can also play hard to get. Just ask Dr Jeff Glaubitz, a molecular geneticist from British Columbia who is working at Canberra with Dr Gavin Moran at CSIRO Forestry and Forest Products. Glaubitz leads a project assessing whether forestry practices such as clear-felling are narrowing the genetic base of native tree species.

The three-year study is taking place near Orbost in eastern Victoria, where the Victorian Department of Natural Resources and Environment is assessing a range of forest management options in its Silvicultural Systems Project. It is part-funded by the Forest and Wood Products Research and Development Corporation.

So far the study has focussed on silvertop ash (Eucalyptus sieberi), the most important harvested species in low-elevation forests of East Gippsland. The silvertop ash differs from the trees Glaubitz is accustomed to. At home in British Columbia, his research centred on western red cedar (Thuja plicata). Although these trees soar to great heights (55 m), there are usually leafy branches not too distant from ground level.

When Glaubitz saw the forests of East Gippsland, he realised the need for a different sampling strategy. The branches of the silvertop ash, which grows as tall as 47 metres, begin way up in the crown, 20-30 m above ground.

How was he to gather leaf specimens from such a height? They couldn't be taken from the forest floor, because their tree of origin wouldn't be able to be determined.

Glaubitz could have adopted the technique of Dr Bernie Hyland, a legendary authority on tropical rainforest trees from CSIRO Plant Industry. Hyland never traipses Australia's northern jungles without a hard hat, a shanghai (slingshot) and a brush hook (long machete).

His method of procuring rare specimens of fruit and blossoms from high up in the canopy is to use his trusty slingshot to catapult a lead sinker and fishing line across a desirable branch, followed by some rope. Often two people are needed to haul down the `captured' limb.

Instead, Glaubitz chose a method favoured by seed collectors from the Australian Tree Seed Centre: shooting them down with a rifle. Assisted by the crack skills of John Owen, Glaubitz was able to gather and catalogue samples from 225 trees in only one week (see More techies' tales)

But the fun wasn't over yet. The next step for Glaubitz was to sample 600 saplings in areas of dense, forest regeneration (minus a machete). The task took three weeks, working from dawn until dusk. `For me this was the hardest work of all,' Glaubitz says. `It's a jungle out there. The site was logged in 1989-90 and the understorey was often incredibly thick. We had to use a compass to mark out the sampling grids.'

After a series of exhausting trips south, Glaubitz had amassed enough material to knuckle down to the next set of challenges: this time in the laboratory. …