Lichens are symbiotic organisms consisting of a fungus and a partner capable of photosynthesis either either a green alga or cyanobacterium. The body of most lichens is different from those of its partners growing separately. The fungus surrounds the algal cells, often enclosing them within complex fungal tissues unique to lichen associations. In many species the fungus even penetrates the algal cell wall. The lichen association is a close symbiosis and extends the ecological range of both partners. However, is not always obligatory for their growth and reproduction in natural environments. Especially the algae can live independently.
Lichens are commonly used to monitor ecosystem health and the impact of atmospheric pollution. In addition, some lichens are potentially valuable sources of pharmaceutical products, including antibiotics, and antioxidants. Despite their occurrence in all terrestrial ecosystems and their overall ecological importance, lichens are commonly overlooked. Furthermore, robust species delimitation and accurate identification remains challenging. There are more than 18, 000 currently accepted species of lichen-forming fungi and an estimated diversity of more than 28, 000 species. On the other hand the number of photosynthetic partners is very low (usually only two genera).
A new study now presents reference sequences using the fungal ITS marker as a DNA Barcode for identifying species within a species complex (Rhizoplaca melanophthalma). Overall, the study demonstrates the potential for accurately identifying lichen species by using DNA Barcoding to identify the lichen-forming fungi. The researchers also formally describe five new species within the group they studied.
As molecular sequence data become more readily available, they will allow us to better understand the diversity of lichenized fungi. Their use in identifying species will become increasingly important and routinely applied. Other disciplines such as ecology, conservation and physiology will benefit from a more objectively based species circumscription, enabling us to interpret distribution and ecological patterns better and more accurately monitor environmental disturbance and climate change.