Patterns and Drivers of Subterranean Biodiversity Hotspots across the Globe

Hotspots of cave biodiversity were mapped globally on the basis of recently published species lists of cave-limited invertebrates and vertebrates. Lists of sites with 20 aquatic or 20 terrestrial cave-limited taxa were mapped on a global scale, with special reference to Pleistocene glaciation, and present-day ecoregions. Twelve sites had 20 or more aquatic species; 17 had 20 or more terrestrial species. Only three sites from the Dinaric Karst had both 20 aquatic and 20 terrestrial species. Aquatic sites were either chemolithoautotrophic or along a ridge at about 45 (Europe) and at about 35 degrees north (in the United States). The terrestrial sites were chemolithoautotrophic or along the ridge but were also found in moist forests in tropics and subtropics. We describe emerging patterns of biodiversity hotspots and discuss the drivers of these patterns, including historical climate change, cave systems density, and resource availability, and highlight conservation challenges associated with protecting these unique ecosystems.