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Queenscliffe Herald Article - April 2007

Symbiosis

By Jill Warneke
Swan Bay Environment Association

At the Community Indigenous Plant Nursery recently we noticed dozens of small iridescent beetles crawling over the bidgee-widgee plants. Closer examination revealed they were eating, or rather sucking, the leaves of the bidgee-widgee. Beautiful though the beetles were we did not want them infesting other species of plants in the Nursery. Luckily the beetles seem only to like the bidgee-widgee, but it set me thinking about symbiosis in nature and the myriad symbiotic relationships existing in the natural world.

A definition of symbiosis is a close relationship between organisms that affects both members, usually to their mutual benefit. A well known example, often shown on nature shows such as David Attenborough, is small fish (e.g. the wrasse) constantly swimming with a larger species. The small fish eat any annoying organisms on the larger fish and are thus kept supplied with a convenient food source while the larger fish are kept clean of lice and other pests.

Coast Beard Heath grows widely throughout the Borough. Its small seed berries, when white and ripe, are eaten by birds, particularly wattle birds. The seed will only re-generate after passing through the gut of a bird, so while the birds get a delicious feast when the seeds are ready the trees get to spread themselves further. At the Nursery we have tried soaking the seed in acid to replicate the birds’ juices with some success. But the natural symbiosis occurring between the birds and the tree is a far more successful method than any we humans can come up with.

Another local example of a symbiotic relationship is the mistletoe bird and the mistletoe plant. The birds eat the mistletoe seeds which are passed through the bird and dropped onto a branch or leaf within 15 mins. The parasitic mistletoe probes its tendrils into the tissue of the tree to use as its source of nourishment. Too heavy an infestation of mistletoe may kill the host tree, but usually healthy trees can support a certain number of mistletoe plants thus providing the birds with a ready supply of its most favoured food.

So the beetle at the Nursery does not appear to be in a symbiotic relationship with the bidgee-widgee as the only benefit seems to be for the beetle. Bidgee-widgee’s relationship with socks and shoe-laces to which the seeds attach themselves ferociously seems more “symbiotic” than with any beetle!  Anyone who has tried pulling them out of their clothing will agree. However bidgee-widgee is a useful re-vegetation plant as it covers and binds the soil and thus helps prevent erosion, so we continue to grow it at the Nursery and release it so it can continue its relationship with sock and laces!

There are many examples of symbiosis in nature and learning about them increases our appreciation of the amazing adaptations plants and animals have made in their evolution.


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