Lost Worlds
There are a few places left where time seems to stand still. Where survivors of a distant Ice Age, huddle together in secret hanging valleys and atop high ridges, isolating themselves from the rest of the world. In these places, live rare and endangered species, that have long ago died out elsewhere, surviving in these isolated places.
Land Islands
Some of these areas have seen the encroachment of civilisation – agriculture, infrastructure and residential development. These places have become islands of biodiversity, isolated from other populations as a result of habitat loss, and the drying out of the continent since the Ice Age, and the loss of disperser species. These islands provide a refuge for these species that are sensitive to environmental conditions, providing a perfect environment where they can thrive.
Expedition to the Secret Black Plum Forest
On Friday 13th December 2024, members of the Black Plum Project, had the privilege to be invited onto private land at Mt Elliott, and to enter the Black Plum Forest, a rare dry vine rainforest, where Planchonella eerwah lives. This is a stronghold of the species, having survived the ravages of time and civilisation.
Cassowary Connection
In this forest, with Mt Elliott looming in the background, we witnessed all stages of the life cycle of this endangered tree from mature fruiting individuals towering out over the forest canopy, to fruit littered at the base of trees, seeds, seedlings and saplings of different heights and ages.
An interesting observation regarding fruit shape was that the more elongated form was prevalent, with few apple shaped forms.
Elliott Bowerman, environmental officer at Sunshine Regional Council, has hypothesised that the more elongated fruit form is better for modern avian fauna dispersal and will be selected for over the larger fruit. Larger fruit may indicate a now extinct large faunal disperser, and that trees no longer are selecting larger rounded fruit forms.
Others have also surmised that possibly a cassowary species that has since gone extinct could have dispersed these large fruits. With the cassowary species extinction, the large fruit were no longer dispersed over long distances, and hence the retraction of the species.
Human Connection
Throughout the forest floor, at the base of many of the trees were observed half eaten fruit. Some animals that are known to feed on the fruit include insects, birds, foxes, bats and feral pigs. Because of the significant size of the fruit, Martin Bennett, an environmental officer from Lockyer Valley, believes that they may hold the key to the dispersal of the fruit, and take over the ecological niche left by the extinct cassowary species. Future studies of examining the stomach contents of feral pigs may assist with this theory.
Indigenous peoples may have also in the past helped with the dispersal of the seed. Martin Bennett recalls what he heard from the late Botanist, Lloyd Bird:
“Lloyd Bird said he was told that the Yuggera/Ugarapul used to carry the fruits in string bags and probably either threw the seeds away on their travels, or more likely in my opinion planting them, as many are along creeks, or moist scrub soils in the area.”
The Black Plum Project aims to bring together knowledge and information through many sources, from scientific research, ground surveys, botanical records, and stories passed on. Martin added:
Great people like the late Lloyd Bird passed on so many stories from their own experience and people way older than him, so he was speaking to people that were in the know in the late 1800s. Yuggera/Yugarapul would have left Booroong’pah (Mount Flinders) and taking plums to eat on their way home, they would have camped at creek where there was water, and planted or thrown the seeds away there, hence why so many are growing on the waterways near there.
Finding Answers
Future molecular testing of individual trees throughout the species range may help in finding answers to the mysteries that this species presents. Each population has over time become isolated from each other, and by delving into the species genetic makeup, we may discover if the isolated populations have evolved to be genetically different. We may also find if some populations show signs of inbreeding, and how we can best help the species.
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