Cladia retipora can grow like snow drifts, explaining its common name of Snow Lichen, while viewed close up, delicate and lacy, Coral Lichen is a fitting name.
This lichen species may be widespread in its native Australasia, but it varies in its growth form, often looking like snow drifts, pillows or flocks of sheep in New Zealand. In Australia, this highly clumped form is rare, and the lichen is more commonly thinly dispersed through heathy vegetation.
Lichens
Lichens are symbiotic associations of a fungus, providing the structure to the body of the organism, with a green or blue-green alga that undertakes photosynthesis. The fungal component anchors the lichen to its substrate, which may be rock, soil or wood or possibly surfaces of buildings or other artificial structures. Minerals and water from the substrate and the atmosphere are taken up and used by both the fungus and the alga, while the latter captures the sun’s energy for use by both partners. The alga benefits from the fungal tissue’s protection from dessication. Neither can grow and reproduce without the other, at least in the wild. Separate components can be cultured separately in the laboratory.
Snow Lichen Taxonomy
Lichens often look like plants, and are classified by some authorities in the Plant Kingdom. It is more usual for fungi to be placed in a separate kingdom, and as lichen taxonomy conventionally follows the classification of the fungal component, Cladia retipora is usually placed in the Kingdom Fungi, Class Ascomycota and Family Cladiaceae.
Distribution
According to the Global Biodiversity Information Facility, the Snow Lichen is found in eastern Australia, including Tasmania and tropical Queensland, with an isolated occurrence in south-western Western Australia. In New Zealand, the lichen is found in both the North and South Islands.
Habitat and Ecology
Lichens are slow-growing, but with the capacity to colonise newly bared surfaces. The ability of the fungal tissue to shrink and curl to conserve water assists the lichen’s survival in harsh conditions, though its reliance on sunlight for photosynthesis means that heavy shade is not suitable habitat. The Snow Lichen shrinks and becomes hard and brittle in dry conditions, but is soft and spongy when water is available.
In New Zealand, tussock grassland and a number of swamp and wetland communities provide habitat for the Snow Lichen (e.g. Mark et al., 1979. New Zealand Journal of Ecology, 2:1-10.) In Australia, exposed rock outcrops with high altitude heath and shrubland are habitat for an unusual pillow form of the lichen in a New South Wales National Park.
Secondary Metabolites
An extraordinary diversity of secondary metabolites have been found in lichens, mostly with function unknown but opening the possibility of present and future medicinal and industrial uses for humans. Theoretically of interest, chemicals can also be used as a taxonomic aid. In 1999, Perry et al. (The Lichenologist, 31:627-636) found that usnic acid was the main antimicrobial, cytotoxic and antiviral component in Snow Lichen.
