Subterranean Biodiversity Patterns from Global to Regional Scales

In the last two decades, there has been a substantial progress in the availability of records for several subterranean taxa, as well as in mapping and statistical modeling of biodiversity patterns. Currently, there is still a large bias toward analyses of aquatic compared to terrestrial subterranean taxa. We provide the first global map of species richness for groundwater crustaceans, indicating that tropics are not hotspots of species richness. Detailed analyses of subterranean biodiversity patterns in Europe show that species richness peaks in regions of mid-latitude, where the beneficial effects of a high productive energy and high habitat heterogeneity have not been counteracted by cold or arid historical events. The range size of European groundwater crustacean species increases northward, a pattern which is best explained by long-term climatic changes. Subterranean species have narrow distribution ranges, which results in a high spatial turnover in species composition across regions and a disproportionally high contribution of regional diversity to total species richness. Within regions, biodiversity patterns are diverse, and their explanations vary across regions, but hotspots contribute only a small proportion of the regional species pool. Molecular approaches to biodiversity studies offer promising research avenues for further documenting and understanding subterranean biodiversity patterns