Synopsis: Comparative Biogeography of Soil-Crust Biota

Abstract

Biological soil crusts most often occur under harsh conditions that include extremes in temperature and light and at least periodic lack of water. They occur in almost all arid and semiarid ecoregions worldwide, and in local arid micro environments in other climates (e.g., temperate regions). Despite their widespread occurrence, comparing the biogeography and ecology of soil- crust biota and communities on a global basis is almost impossible. This is because most of the data were collected (1) using different methodologies, (2) using different taxonomic systems [e.g., using Drouet’s (1956) keys, where he combined genera], and/or (3) were focused on a single group of organisms (i.e., lichens, algae, cyanobacteria, or mosses) to the exclusion of other groups.