Competition and Interactions Between Organisms - Ecological world

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Tuesday, 17 January 2017

Competition and Interactions Between Organisms



             Except for axenic laboratory cultures, there are only a few cases in which a natural substrate remains occupied by only one species. A known case is Oudemansiella mucida in standing, but dead trunks of Fagus sylvatica due to the production of the antifungal compound, mucidin. Instead, nearly every substrate accessible to fungi can support more than one species (Rayner and Boddy 1988), that is, various fungi and bacteria compete for space, nutrients, water, and air. 




Each fungus has its own strategy to withstand competition. Competition may occur between species and between mycelia of the same species. As a result of the latter, wood colonized by Trametes versicolor shows that the individual colonies form black barrier (demarcation) lines, where the different mycelia have interacted with each other to inhibit further movement of each mycelium in the region of contact. Different parts of the same mycelium and even adjacent hyphae may compete. 

For example, reproducing hyphae might consume more nutrients and thereby affect the vegetatively growing hyphae. There are three main categories of the strategies or adaptations to ecological niches (Jennings and Lysek 1999). Through combative strategy, the fungus defends the substrate that has already been captured or attacks competitors occupying a substrate that is capable of capture (e.g., 0. mucida). Through ruderal strategy, a substrate as yet unoccupied or only partly colonized is exploited. Those fungi do not attack potentially resistant substrates but degrade readily consumable or unusual compounds, like Pholiota carbonica (Europe, North America, Asia, North Africa) and P. highlandens-is (USA), which both grow on former fire sites (Breitenbach and Kranzlin 1995). 

So these fungi occupy a substrate faster than possible competitors. Fungi concerned in the stress-tolerant strategy are adapted to environments that are too harsh for possible competitors. Examples for the latter are the soft-rot fungi growing in very wet timber of low air content. 
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