Fungal ecology

Introduction

Fungi show a wide range of behaviours and interactions. There are numerous interactions, both between different species of fungi and also between fungi and other organisms. Over time there may be a change in the species present in any area. Certain species are quick colonizers of disturbed areas – but are then replaced by others. Some species develop rapidly, reproduce quickly and then die whereas others are longer lived. Then there are those which are found in limited habitats whereas others can turn up almost anywhere.

Given the scope of the subject, there will necessarily be a very limited coverage in this section. There will be specific references for many of the topics. You can also find some general references, which provide good starting points for further study, by clicking on this button.

Eucalypts are one of the dominant plant genera in Australia and are found throughout the country. An overview of fungi associated with eucalypts is given in the reference in this button.

A note about microfungi

The introduction to this website explained the difference between macrofungi and microfungi. The macrofungi are those that produce the easily visible fruiting bodies such as mushrooms, puffballs, polypores and so on - while the microfungi are the moulds, plant rusts, smuts, mildews and so on.

This website is devoted to the macrofungi, with the microfungi getting only an occasional mention. That’s not because there are few microfungi. In fact there are far more microfungi than macrofungi. It’s also not because the microfungi are unimportant. On the contrary, they are exceedingly important from both ecological and economic points of view.

Virtually all the examples given in this ecology section are macrofungal. However, for almost any example of macrofungal behaviour, lifestyle and interactions you could find microfungal examples of the same behaviour, lifestyle and interactions.

The restriction to macrofungi is simply because those are the fungi dealt with at the Australian National Botanic Gardens. While this restriction excludes the bulk of the fungal world, the macrofungi are still a very varied group and give a tremendous scope for study.

Finally, the macro and micro fungi do interact - as shown by the accompanying photo of a mouldy mushroom in the genus Cortinarius !

The three fungal lifestyles

While there is no single fungal lifestyle, one thing common to all fungi is that (unlike the green plants, for example) they do not make their own food. Fungi get their nutrients from existing organic matter and there are many sources of organic matter in the world - leaf litter, dung, soil, animals, dead wood and living plants - to name just a few. Fungi use them all.

A fungus that feeds on dead organic matter is a saprotroph. Fungi that get their nutrients from living organisms do so in a variety of ways but can be put into two broad categories. Where there is no benefit to the other organism, the fungus in question is a parasite. If there is some benefit to both the fungus and the other organism, the fungi are mutualistic. Note that in mutualistic associations, the benefits need not be equally shared. You will often see the word symbiotic used to describe associations between different organisms and that word literally means "living together". It’s a general term covering all types of associations, with no implication about the nature of the association. Hence, parasitic and mutualistic are two examples of symbiotic associations.

Agaricus is a common genus of saprotrophic fungi. The ordinary Field Mushrooms belong to this genus and you will often see various Agaricus species growing in gardens, parks and paddocks. In such situations the mycelium is feeding on dead organic matter in the ground. Commercially, Agaricus is grown on composted plant material. Other commonly seen examples of saprotrophs found on the ground are the Shaggy Inkcap (Coprinus comatus ) and Marasmius oreades (which often forms fairy rings in lawns).

Cyttaria gunnii fruiting boody growing from gall.

Some parasites have very specific host requirements, whereas others may parasitize a variety of species or genera - and not all parasites kill their hosts. For example, Cyttaria gunnii is found in Australia and New Zealand and grows on live Nothofagus trees. In fact, all species of the genus Cyttaria grow only on Nothofagus, a plant genus found in Chile and parts of Australasia. Though Cyttaria grows on live trees, the trees are not killed. The fungi may cause galls in the trees, as shown in this photo of Cyttaria gunnii fruiting bodies growing from a large, fungally-induced gall on a Nothofagus tree in New Zealand. Another example is Cyttaria nigra from New Zealand.

The three terms saprotroph, parasite and mutualistic are very useful descriptive terms, but a fungus doesn’t necessarily stay put in one pigeonhole. For example, some fungi are always saprotrophic, some are always parasitic and some are always mutualistic - but there are also those which, depending on circumstances, may change behaviour.

Remember that wherever there’s organic matter, there’s almost certainly some fungus that will exploit it. Some years ago there was a display of sub-antarctic plants in the visitor information centre of the Australian National Botanic Gardens in Canberra. The plants were held in a refrigerated cabinet but the cabinet leaked water onto the carpet (which was lying over a concrete floor) and created suitable conditions for a species of Peziza to grow there. Peziza is an ascomycete genus and produces fruiting bodies that are generally cup-like or disk-like, though at times distorted in form. These photos show a close-up view of the fruiting bodies as well as a drawn-back view showing the leaking corner of the cabinet.

Mycorrhizas - associations between fungi and plants

An important type of mutualistic relationship is the mycorrhizal association between fungi and plants. The word mycorrhiza is derived from the Classical Greek words for 'mushroom' and 'root'. In a mycorrhizal association the fungal hyphae of an underground mycelium are in contact with plant roots, but without the fungus parasitizing the plant. In fact the association is commonly (but by no means always) mutually beneficial. Through photosynthesis a chlorophyll-containing plant makes simple carbohydrates (using carbon dioxide, water and sunlight). About 90% of plant species form mycorrhizas and in many of these associations between 10% and 30% of the food produced by the plant moves through to the fungi. The associated fungal mycelia are adept at extracting minerals, especially nitrogen and phosphorus from the soil and these pass through to the plants. Mycorrhizal fungi can also protect plants against pathogenic fungi and micro-organisms. All in all, mycorrhizal fungi are very important for plant health.

You will find mycorrhizal associations from well-watered forests to the arid areas. The eucalypts, almost synonymous with Australia, are mycorrhizal, as are other genera in the same family (the Myrtaceae) - for example, Kunzea, Leptospermum and Melaleuca. Outside the Myrtaceae the genera Acacia, Casuarina and Nothofagus are further examples of common mycorrhizal genera. So, whenever you’re looking at a gum tree, a tea-tree, a she-oak or a wattle - think about the fungal partners in the soil. Many of the imported garden trees in Australia are also mycorrhizal, for example beeches, oaks, firs and pines.

This has barely skimmed the surface and you can find out more in the MYCORRHIZAS SECTION.

Fungal ecology

Introduction

A note about microfungi

The three fungal lifestyles

Mycorrhizas - associations between fungi and plants

LINKS TO 6 OTHER SECTIONS