Map Lichen

Rhizocarpon spp.

Map lichen are broadly distributed worldwide and can be found almost anywhere with cold exposed rock surfaces. They come in a variety of colours. In the case of the classic Rhizocarpon geographicum, each individual lichen consists of a green thallus surrounded by a thin black line of rhizomes. A group of them together is irresistibly reminiscent of a map, particularly when they live together with other Rhizocarpon species (as in the right-hand photo above).

Map lichen are famously long-lived, and have been used to date historical and even geological specimens. They have also been deliberately exposed to the cold of space, which did not seem to cause them any distress.

For a definitive descriptive list of Australian Rhizocarpon species, see this article by Patrick M. McCarthy and John A. Elix in the magazine Telopea.