Lichens are found in terrestrial biomes worldwide.They are dual organisms composed ofa fungal and a photosynthetic partner.Lichens characteristically grow in low nutrient environments such as on rocks or tree bark,or on poorly developed soils,which may be subject to extreme temperatures and prone to desiccation.Such habitats are particularly abundant in the Subarctic,Arctic and Antarctic where lichens are of great ecological importance and where global warming and climate change pose an especial threat.Despite their prevalence,many aspects of the biology of lichens remain unknown.This is in part due to their slow growth rates and the difficulty of in vitro culture.However,the advent of molecular techniques has allowed novel investigations.