2.1 Black fungi inhabiting rock surfaces

Fungi represent one of the most diverse and ancient branches of the tree of life and have a worldwide distribution. They successfully colonize every biome, including extreme environments such as polar and desert regions, playing a pivotal role in global biogeochemical processes. In the fungal kingdom, “black fungi” (or microco-lonial fungi or meristematic fungi) are a slow-growing group that reproduces mostly asexually; it includes ascomycetous taxa that are phylogenetically quite heterogene-ous in the classes Dothideomycetes, Eurotiomycetes, and Arthoniomycetes. In contrast to the majority of fungi, which live more or less comfortably inside their hosts or substrates, few black fungal lineages have evolved and adapted to thrive on bare naked rock surfaces (e.g., in the Mediterranean basin or in hot and cold dry deserts) and are therefore referred to rock-inhabiting fungi (RIF). For their ability to thrive in harshest conditions such as drought, temperature and pH extremes, exces-sive radiation, and oligotrophy, RIF are accounted as the most resistant eukaryotic organisms known to date. In this chapter, we will provide an overview of the diversity, taxonomy, occurrence, and ecology of RIF colonizing both worldwide natural rocks and stone monuments, also exploring the future perspectives, including their bio-technological, bioremediation, and radioprotection potentialn