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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Apr 29

Symbiotic Relations

Posted on April 29, 2016 at 7:36 AM by Ann Vallee

by Charlene Burgi

A friend recently recounted all the various peonies found in the garden of her childhood. Peonies were her mother's favorite flowers, she noted. But though the flowers were beautiful, they attracted ants. As a result of this ant invasion, she opted not to introduce these gorgeous flowers into her own garden. Her comment prompted me to learn the reasons for the ant attack, since peonies are central to the design of my garden and are planted throughout.

Peony flower bud
Peony flower bud
My research found ants are attracted to the peony's large, bulbous buds. I also came across the wives' tale that peony buds won't open without ants swarming over the flower head. I had to laugh at the lack of science, as the disclaimer noted some buds might open even without the presence of ants. All of this raised the question of the function of the ants in relation to the flower.

I did learn there is a very good reason for the ant population's attraction. Peony flower buds produce a sweet nectar in glands located along the outside of the undeveloped buds. This attractant seems like it would be of no benefit and only a bother to the flowers—and most assuredly to the gardener wishing to display these cut beauties in the house! However, the army of ants seem to ward off any other pests that could do more damage to the flowers. 

By definition of a symbiotic relation, the peony is not dependent on the ant for survival (though possibly it benefits from these bodyguards—and we certainly benefit through our enjoyment of a floral bouquet untouched by harmful insects!) The ant is partaking of the commensalism type of relationship—one organism benefiting from the other without causing clear harm or benefit. This is classified as a one-way symbiotic affair.

There are many other types of symbiotic relations that occur in the garden where both organisms benefit. One type is called a mutualistic relationship. For example, the bee pollinating our garden is helping herself to the makings of honey found in the flowers. As she buzzes around dusting the plants with pollen, she meets the plant's need for fertilization. The bee is fed and the plant reproduces.

Parasitism is another type of symbiotic relationship found throughout our gardens. Consider the aphids and scales sucking the life from our plants. These are one-way relationships that benefit the predator but cause the harm or demise of the plant.

Lastly, ectosymbiosis and endosymbiosis sound like destructive terms, which is true. However, these relationships sometimes can be beneficial for our gardens. For example, ectosymboisis is one species living on the surface of another. The parasitic wasp is a great example of a positive effect, as it lays its eggs on caterpillars. The larvae from the wasps feed off of the caterpillars and destroy these predators attempting to devour our plants. Endosymbiosis, on the other hand, is one species living inside another. If you ever witnessed borers eating the cambium layer of your tree, you have witnessed endosymbiosis. In due time you may also witness the demise of your tree, as the parasitic species eats away the very mechanism for the tree to take up nutrients.

Symbiotic relationships. They are all around us. Some are beneficial and help keep our gardens healthy and thriving, other types are harmless, while still others just make you want to go in and take a shower!

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