Forgetful rats and ancient fruits

On the left, fruits of Eidothea from 15-20 million years ago. On the right, fruits of the same genus from just over ten years ago.

Have a look at the ABC Science page and read all about our Rainforest Seed Project (led by Dr Kim Hamilton) and our conservation genetics research on rainforest plants (led by Dr Maurizio Rossetto). See Rainforest Fruit Power and skim down to the second half of the story. Better still, read the whole story but make sure you keep reading to the end!

You'll learn, for example, how 'the critically endangered Nightcap Oak (Eidothea hardeniana)...depends on the forgetfulness of native bush rats'.

The Nightcap Oak is a bit of favourite of mine. It's the poor-[Public Relations]-man's Wollemi Pine, and I was working at the Royal Botanic Gardens in Melbourne when the genus Eidothea itself was first described by Dr Andrew Douglas and colleagues.

Eidothea was named in 1995. At the time it was thought to include only one species, Eidothea zoexylocarya, which grows on Mt Bartle Frere, near Cairns in North Queensland. Eidothea is in the plant family Proteaceae, along with more familiar and often spectacular members such as the waratahs, grevilleas, banksias, macadamias and proteas.

It had/has a fascinating fruit, a bit like a Macadamia on the outside but inside reminiscent of a walnut in cross-section. What is really interesting is that a similar fruit is illustrated in a book published in 1860. In this case, the fruit was a 15-20 million year-old fossil found in the Victorian goldfields by the State Government Botanist of the day, Baron Ferdinand von Mueller.

The fruits were so unlike those of other Proteaceae that Mueller misidentified the fossils as belonging to something in the olive family. It was not until the fossils were matched with fruits from living Eidothea trees that their true identity was revealed. A bit like the Wollemi Pine story!

That Eidothea has been found at localities as far apart as Cairns, Lismore and Ballarat, also underlines the fact that Australia’s rainforests are tiny remnants of ancient rainforests that covered vast areas of Australia until only a few million years ago. This makes them a particularly precious part of our natural heritage.

And there's more... The story of how the rare species from the Nightcap Range was discovered is equally amazing. The prickly juvenile leaves of the Nightcap species were first found in the 1950s and sent to the Queensland Herbarium in Brisbane, where they were incorrectly identified as belonging to the Corynocarpaceae, a plant family only distantly related to the Proteaceae.

Over forty years later, Robert Kooyman, then a forest ecologist with State Forests of New South Wales, also noticed the unusual juvenile leaves sprouting from the base of a large tree trunk but found them impossible to identify. After leaving State Forests, he was contracted by the National Parks and Wildlife Service to conduct surveys of rare or threatened plant species in Nightcap National Park, bringing him back to his mystery trees.

The next time he encountered one, he noticed a patch of exposed dead wood on the trunk, which revealed the distinctive wood grain of the Proteaceae. Kooyman collected foliage, wood and rat-gnawed fruits and sent them to the Botanic Gardens Trust in Sydney for identification. Our scientist Dr Peter Weston, who specialises in the classification of the Proteaceae, was then able to confirm that the new species is an Eidothea.

There are about 100 adult plants of the Nightcap Oak in its natural habitat, which makes it about as rare as the Wollemi Pine. But if you want to find about the forgetful bushrats, see Rainforest Fruit Power ...