Yellow Rhizocarpon sp. lichens, growing on bare rock, Snowdonia National Park, Wales, UK.
Lichen Rhizocarpon species of the R. geographicum group, a species complex with several taxa which often require microscopic characters for exact identification. Light loving species from acidic rocks – many of them are pioneers which colonize rocks rather quickly but once established they can stay for very long periods – up to hundreds of years and they are used in the so-called lichenometry for dating of glacial moraines or monuments (based on “calibrated” thalli eg. from nearby graveyards with dated tombstone the average annual growth rate is calculated and using this data the age of the moraine, monument or whatever is the object of interest is estimated.). There are more than 1700 species of lichen in Britain. Approximately 18000 species of lichen have been described and identified worldwide. The algal partners in lichens can be found living on their own in nature, as free-living species in their own right. The fungal partners in British lichens are recognizable Ascomycetes or Basidiomycetes. However, they have come to need the right kind of algal partner in order to survive. Unlike other fungi or indeed their algal partner, they cannot survive on their own. Of the more than 1500 genera of algae worldwide, relatively few make suitable lichen partners. In Britain, only three genera, Trebouxia, Trentepohlia and Nostoc are common fungal partners. Interestingly, the same alga can combine with different fungi to produce entirely different lichens. The same fungus can also form different lichens depending on the type of alga which it associates with. Most lichens contain only one kind of alga, but some may contain two. Identifying the type of alga in a lichen may be difficult, as they frequently look different to the free-living forms. The fungal partner forms the main body of the lichen, with the algal cells either scattered among the fungal hyphae, or arranged in a layer just below the upper surface of the lichen.
Size: 4534px × 2480px
Photo credit: © Scenics & Science / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ascomycetes, bare, basidiomycetes, growing, indicators, lichens, national, park, pollution, rhizocarpon, rock, snowdonia, sp., trebouxia, trentepohlia, uk., wales, yellow
