Biotic Interactions – The Essence of Nature Conservation
16 April 2025
There was a good turnout for this year’s Serventy Memorial Lecture (SML), including many non-members. Don Poynton began by talking about the WA Naturalists’ Club, its origins in 1924 with the Serventy family, our branches, our major projects and our publications, and reminding us of all the events the Club put on last year for our Centenary (see website summary posted Jan 2025). He also outlined the role of the Serventy Memorial Lecture (SML) in raising money to help tertiary students in the field of Natural History, and that so far, 80 students have benefited.
Don then handed over to Terry Houston, who introduced our speaker, Byron Lamont AM, Distinguished Professor Emeritus in Plant Ecology at Curtin University. Terry said he had enjoyed working with Byron for many years and that he was a good collaborator. Byron’s expertise is in the ecology of the flora of the South West Botanical Province of Australia, and he earned his PhD researching the proteoid roots of Hakeas and his DSc on the general ecology of the family Proteaceae. His publications include over 250 journal papers, two books and 150 review articles.
Byron began by explaining the different types of biotic interactions between species. Competition is one. Symbiosis is another, and ranges from mutualism, in which both species benefit from the relationship to parasitism, in which one member is harmed and the other benefits. Lichens are a prime example of mutualism, in which a fungus provides the substrate for an alga, holds water and produces antibiotics via yeasts, while the alga provides sugars to the fungus.
Byron then presented several examples of interactions between species in the South West. One of these is self-crypsis in Hakea trifurcata. Carnaby’s Black Cockatoo feeds on the high-protein Hakea seeds. But the Hakea has evolved a trick to protect its valuable seeds. In the mature plant, some of its leaves (typically narrow for drought tolerance) are broad and resemble the fruits. Byron has shown with Philip Groom that this confuses the cockatoos, which eventually give up looking for fruits.
Hakeas and honeyeaters have evolved together, with the birds pollinating the bright flowers while feeding on the nectar. But hakeas have to protect their flowers from being eaten by cockatoos. So, they surround their flower heads with spiny leaves and have cyanide in the flowers, which are often coloured red as a warning sign. Also, the thick, woody fruits of Hakeas deter cockatoos from eating the seeds while also protecting the seeds from fire.
The fungus Drechmeria drops its spores into leaf litter. The Ghost Moth caterpillar ingests the spores, which germinate into hyphae that cause the caterpillar to turn vertically and then die. Then, the fungal fruiting body grows from its head and completes its life cycle. The fungus depends entirely on the caterpillar. In the Himalayas, a caterpillar fungus is in danger of extinction because people harvest the mummified bodies to sell for its supposed medical benefits.
Another type of interaction is orchid mimicry. The orchid Diuris magnifica resembles the pea Daviesia divaricata in color, shape and flowering time but provides no nectar for pollinators. Native bees, familiar with the pea, go to the orchid in search of nectar, carry off the pollinarium and usually pollinate another Diuris magnifica without getting a reward. However, the introduced honeybee doesn’t return to the orchids and so fails to pollinate them.
The Underground Orchid Rhizanthella depends on a mycorrhizal fungus, which obtains inorganic nitrogen from the soil and carbohydrates from a Melaleuca and passes them on to the orchid. So, the orchid is entirely dependent on the fungus and the Melaleuca.
Woylies often shelter under the Heartleaf Poison Gastrolobium bilobum, burying its seeds with their digging. But they also dig for the fruiting bodies of underground fungi (native truffles) and spread the spores in their faeces. These fungi are mycorrhizal, so they help enormously with the growth of peas and other plants. So, the loss of the Woylie would be detrimental to the overall functioning of the ecosystem.
The Albany Pitcher Plant produces sugary nectar around the rim of its pitcher, in which nematodes live, along with bacteria that produce chitinase that dissolves the exoskeleton of hapless insects. A wingless fly, Badisis, whose larvae also live in this “soup”, resembles the Stick Nest Ant and may serve to lure these ants to the deadly brew.
At Mt Lesueur, Banksia tricuspis is host to the Banksia Moth that lays its eggs in the flower heads and destroys them. But Carnaby’s Black Cockatoo detects the larvae in the flowers and eats them. Although the cockatoos destroy an additional 8% of the flowers, the 74% possessing moth larvae are reached by the cockatoos. So, the loss of the cockatoo would likely result in the eventual extinction of the Banksia, which is also a source of food for the Honey Possum.
The adult foliage of the Woolly Bush Adenanthos cygnorum produces extrafloral nectaries (EFNs). There is a moth that lays its eggs on the nectaries, hatching into destructive larvae. But a parasitoid wasp detects the larvae and deposits eggs on the pupae. Also, ants attracted to the EFNs deter destructive insects, such as Snout Beetles. This is biological control. The seeds, held in a cup of leaves, are taken by ants into their nests, protected from ground-dwelling seed-eaters, where they may germinate. So, the wasps and the ants enhance the survival of the Woolly Bush.
These examples that Byron presented to us illustrate how all species are intimately related to others. This is the essence of conservation. The loss of even one species will have a ripple effect throughout the ecosystem. Exotic species disrupt interactions between species, and land-clearing decimates populations. Byron said that although scientific research is generally growing rapidly, unfortunately, field studies and documentation of new species are declining.
Mike Gregson