The mid‐latitude biodiversity ridge in terrestrial cave fauna

Abstract

The world's obligate cave‐dwelling fauna holds considerable promise for biogeographic analysis because it represents a large number of independent evolutionary experiments in isolation in caves and adaptation to subterranean life. We focus on seven north temperate regions of at least 2000 km2, utilizing more than 4300 records of obligate cave‐dwelling terrestrial invertebrates. In North America, highest diversity was found in northeast Alabama while in Europe highest diversity was found in Ariège, France, and in southeast Slovenia. Based on these regions as well as more qualitative data from 16 other regions, we hypothesize that a ridge (ca 42°–46° in Europe and 34° in North America) of high biodiversity occurs in temperate areas of high productivity and cave density. This may reflect a strong dependence of cave communities on long term surface productivity (as reflected in actual evapotranspiration), because the subterranean fauna relies almost entirely on resources produced outside caves. This dependence may explain the unique biodiversity pattern of terrestrial cave invertebrates.

VIEWPOINT. Is the Australian subterranean fauna uniquely diverse?

“…Slovenia, a key cave region in Europe, has 114 known stygobitic species (Culver and White 2004), while six other European countries (Belgium, France, Italy, Portugal, Slovenia, Spain Michel et al 2009)) have recorded 1059 stygobitic taxa with no more than 80 species from any one karst region. Most of these taxa are considered remnants of the Pleistocene, during which time cave populations were colonised during interglacial cycles, and isolated during glacial periods (Peck 1984;Peck and Christiansen 1990;Culver et al 2006). However, this is likely not the sole source of species origins with pre-Pleistocene processes being well recognised (Hedin 1997;Buhay and Crandall 2005;Buhay et al 2007).…”

“…However, this is likely not the sole source of species origins with pre-Pleistocene processes being well recognised (Hedin 1997;Buhay and Crandall 2005;Buhay et al 2007). Culver et al (2006) predicted that other regions of interest for cave fauna in the northern hemisphere are likely to include the Eurasian continent including Georgia and Kyrgyzstan. Alternatively, the southern hemisphere subterranean fauna are well documented for New Zealand, where 102 described species are known from groundwater habitats, particular Hydracarina (70 species) and crustacean groups such as Amphipoda (four species), Isopoda (four species), and Syncarida (seven species) (Scarsbrook et al 2003).…”

“…Globally, the northern hemisphere dominates as a region of subterranean biodiversity hotspots, in particular temperate midlatitude locations (Culver et al 2006;Stoch and Galassi 2010) such as the Balkan Peninsula, the USA (Culver and Sket 2000), Mexico (Reddell 1981) and, most recently, caves of south-east Asia (Deharveng 2005). Subterranean faunal diversity is generally concentrated in karst and pseudokarst areas (Juberthie and Decu 1994;Culver et al 2001;Christman et al 2005;Deharveng 2005).…”

A new Eukoenenia species from the Caucasus bridges a gap in the known distribution of palpigrades (Arachnida: Palpigradi)

“…The subterranean fauna is probably likewise rich, especially in the karstic massifs of the Western Caucasus (Sendra & Reboleira 2012), as indicated by the current increase in the number of cave-dwelling species in certain arthropod groups such as arrhopalitid collembolans (Vargovitsh 2012(Vargovitsh , 2013. According to Culver et al (2006), habitat availability (inferred from the density of caves) and long-term productivity (measured by temperature and rainfall) best predict density of troglobiont species at a landscape scale. Hence great subterranean biodiversity may be expected in those ranges of the Western Caucasus where high cave density is combined with a warm-humid climate.…”

Escherichia coli, other Coliform, and Environmental Chemoheterotrophic Bacteria in Isolated Water Pools from Six Caves in Northern Alabama and Northwestern Georgia

“…Many bacteria in caves are considered non-native species that have been transported into a cave via water, air, or animals (Northup and Lavoie, 2001), and how these bacteria interact and compete with endemic microflora is unknown. Alabama and Georgia are caverich states (Culver et al, 2006) that offer opportunities for microbial studies. Most caves in these two states are found in the Appalachian Plateaus and Interior Low Plateaus physiographic provinces and are formed in fossiliferous Paleozoic limestone.…”