Hygrocybe is a genus within the Hygrophoraceae. Members of the genus are found around the world, though basidiomes are collected most commonly in warm temperate to humid climates. The fungi form brightly coloured, small to medium sized basidiomes commonly in autumn. Of the few fungi that have been examined, the mode of feeding appears to be saprotrophic, with a degree of specificity for particular substrates. Some members of the genus form ectomycorrhizas, with a high degree of specificity for host tree. LINK Many species are known to be highly sensitive to pollutants such as nutrient enriched water, organic materials and heavy metals. The fungi appear to have highly specific requirements for growth and survival, and thus might be susceptible to changes in the environment.
Basidiomes of several rare species of Hygrocybe have been found in Lane Cove Bushland Park (Sydney, Australia). Lane Cove is an area of high-density housing located close to the CBD of Sydney. Local residents were concerned that encroaching urbanisation of the bushland and associated increase in pollution might cause the extinction of some of these fungi. Lane Cove, like much of Sydney, has an increasing density of housing, and all areas of bushland are viewed as potential sites for either light industrial or urban development. In Lane Cove, the increase in runoff, especially if polluted, might degrade the habitat to the point where the fungi would become extinct. Thus there might be a case to conserve these fungi in their native habitat by protecting the habitat from incursions.
Preservation of habitats is one way in which rare species might be conserved. Most fungi can be cultured, though some with great difficulty. Thus alternative approaches include transfer of the fungi to similar habitats, and conservation in vitro. Great care must be taken when determining whether to and what is the best way to conserve fungi. If habitat preservation is considered, what steps are necessary to determine whether the site should be preserved?
In Australia, fungi have never been the basis of a protection order of any magnitude. Many animals and plants are protected to varying degrees, usually on the basis that the species can become extinct if not protected. However, many fungi can be cultured in artificial conditions and their genetic material stored. The function of most species of fungi is not clearly understood so the reasons for alternative approaches to conservation are unclear. Also, we are aware of a number of saprotrophic and ectomycorrhizal fungi that have the potential to fill the role of Hygrocybe. Thus the first step might be to determine if the fungi are truly rare.
Collections from across Lane Cove Bushland Park were sorted and passed to a mycologist who, fortunately, was examining Hygrocybe of the east coast of Australia. The collections were meticulously catalogued. Information on time and location of collection recorded. The vegetation of the park was also classified to provide a basis for determining the conditions necessary for survival of the fungi.
Over the period 1996 to 2000, hundreds of basidiomes were collected and examined. The fungi were classified into more than 20 species of Hygrocybe, and one species of the closely related Camarophyllopsis. Of those collected, 10 were undescribed. However, as happens when any genus is subject to very close scrutiny, gradations of form between species were found. These fungi were subjected to a more detailed examination, and it became clear that traditional techniques of classification using morphological, especially microscopic, detail were inadequate. Molecular techniques were used, and at the time of writing, had not clearly resolved the appropriate group to place many of the collections.
The first goal was to determine whether the fungi were rare. Of the more than 23 species of Hygrocybe at the site, five are believed to be unique to the site. A further species of Camarophyllopsis is also unique to the park. Several variants of two further species, H. anomala and H. austropratensis were found and these appear to be genetically distinct from members of the species found elsewhere. Support for rarity is based on two arguments: that the fungi have not been discovered elsewhere, and that the site appears to support the various conditions necessary for survival of many members of the genus.
The distribution of the fungi throughout the Park is based on appearance of basidiomes. The fruiting bodies appear after environmental conditions trigger movement of stored organic carbon in to specific parts of the thallus. LINK Basidiomes only appear when conditions are suitable for fruiting. The fungus could exist elsewhere without fruiting, and fruiting need not indicate the extent of the mycelium. Molecular techniques may indicate the extent of the fungi once appropriate markers for each taxa become available.
Basidiomes are brightly coloured, and therefore apparently obvious. However, they appear for only a short period of time before collapsing. Thus, basidiomes will be found by a collector interested in that group of fungi only if the collector comes upon them at the time of fruiting. Systematic searches for fruiting bodies by collectors are often limited, due to the few collectors being able to identify or interested in each group of fungi, and because of the huge areas available for collecting. Mycological taxonomy is a small field of research in Australia, and a huge number of fungi remain to be classified. Therefore, any suggestion that a species is rare needs to be tempered with the understanding that our knowledge of their distribution is severely limited.
The Lane Cove Bushland Park is a small, highly diverse habitat. The vegetation ranges from depauporate rainforest to dry sclerophyll woodland. The topography is undulating, with streams dissecting ridges running north/south. Thus hill tops will receive intense irradiation during summer, and the valleys will be largely protected under dense vegetation. Further, the streams will humidify the air, making conditions suitable for fruiting for longer periods in the valleys than on the ridges. The Park contains the conditions to support a variety of fungi with different growth requirements.
Finally, the conservation of fungi is commonly supported by arguments that fungi produce a range of secondary metabolites with potentially unique and economically valuable attributes. LINK These attributes have been tested in the case of only a few fungi. In the case of Penicillin and Trichoderma, a huge diversity of potentially valuable metabolites has been discovered. Use of sophisticated analyses has resulted in the discovery of quite unusual molecules. Few of these molecules have been developed successfully to the stage of a commercial product. LINK Testing requires the capacity to culture the fungi, as well as test for attributes of unknown potential. This appears simple from the surface, but testing requires the development of a simple assay, usually bioassay, with a clear target. Thus while it is easy to hypothesise potential attributes, the determination of activity even against specific targets is difficult and expensive. Commercialisation is suggested to cost around 1000 times the cost of finding the active ingredient. Searching for novel metabolites is probably an argument that should be used with extreme care.
In the case of Hygrocybe, the use of the argument is supported by field observations. Some basidiomes appear able to deter pests. In the field, basidiomes commonly deteriorate rapidly due to feeding by mites, insects and slugs. Absence of feeding indicates the presence of a mechanism with broad application. Fungi, however, also contain some extremely toxic compounds, and the activity against arthropods may in addition affect mammals and even plants. LINK
Finally, the fungi have not yet been cultured so determination of industrial potential and conservation via in vitro storage remain untested. Basidiospores have been plated out on media. However, no spores have germinated. This is not surprising as many fungi have dormant spores. LINK It may be possible to take hyphae from young basidiomes and culture the hyphae on media. This process has been used to grow ectomycorrhizal basidiomycetes and many wood rotting fungi. It may succeed with Hygrocybe.
Both state and commonwealth legislation has been enacted to prevent destruction of important biological resources. In NSW, the main act is the Threatened Species Conservation act. Under this legislation the site was registered as being threatened on the basis that:
Determination that a site is threatened is only one approach for conservation of fungi. The site was also placed on the Register of the National Estate. Registered sites are places that have special value for present and future generations. Sites may then be eligible for support from commonwealth sources to ensure they are protected. Successful listing on the National Estate is particularly important. This is the first occasion that fungi have been registered as being worth preservation. Fungi are seen as being part of the biological component of our cultural and aesthetic heritage. The precedent has been set.
The process is also important for it illustrates the very important role played by amateur enthusiasts, their scientific collaborators, and the political and legislative structures established for just this purpose. Enthusiasts often have highly detailed understanding of the local conditions and processes. Scientific support is needed to place the information in a larger context, and the political structures legitimate the endpoint: conservation. The conservation of the site on the basis of the fungi present at the site, vindicates the enormous effort of locals and the scientists who assisted them. Further studies may now proceed knowing fungi are accepted as an important component of our biological heritage.
Kearney R & Kearney E. (2000) Significance of the Hygrocybeae community of Lane Cove Bushland Park in listings under the NSW Threatened Species Act 1995 and under the Australian Heritage Commission Act 1975. Australasian Mycologist 19, 64 - 70.
Young AM, Kearney R & Kearney E. (2001) Additions to the Hygrophoraceae of Lane Cove Bushland Park. Australasian Mycologist 20: 79 - 86. Copyright University of Sydney.
FungiBank - information about Australia’s rich resource bank of native fungi: http://www.fungibank.csiro.au