Yellow Navel

This little mushroom is the yellow navel fungus or the Lichenomphalia chromacea (it used to be called the Omphalina chromacea).  It is a member of the fungi group Basidiolichens, which rely on symbiotic associations with algae.  You can’t always see the algae as it is often in damp areas and surrounded by moss, like these ones.  The Lichenomphalia is the fungal component of a lichen (a symbiosis between an alga and a fungus). The fungus produces spores, whilst the algae Coccomyxa, produces photosynthetic products.

The Yellow Navel caps start out convex with a scalloped margin and a central depression.  As the fungus matures, the cap flattens and then becomes funnel-shaped, which is when it looks like a navel or belly-button which gives it its name.  These were less than 10mm across, but the species can grow up to 25mm across.  It is native to Australia and found in native forests in the south-east and south-west.

If you want to read more, there is a scientific paper about these symbiotic associations and the concentration of mutualistic species in specific taxonomic groups that suggest that mutualism is an important evolutionary mechanism in the evolution of fungi, cyanobacteria, algae and land plants.  ….Such a group of fungi, the genus Omphalina, was recently proposed as a model system for study of evolutionary mechanisms associated with lichenization……