The North American obligate cave fauna: Regional patterns

The obligate cave faunas of nine regions of the United States - Florida Lime Sinks, Appalachians, Interior Low Plateaus, Ozarks, Driftless Area, Edwards Aquifer/Balcones Escarpment, Guadalupe Mountains, Black Hills, and Mother Lode - are described and compared. The number of aquatic (stygobitic) species ranged from zero (Black Hills) to 82 (Appalachians), and the number of terrestrial (troglobitic) species ranged from zero (Florida Lime Sinks) to 256 (Interior Low Plateau). Even at the level of genus, overlap between regions is low. Several predictor variables (karst area, number of caves, number of long caves, number of deep caves, distance from the Pleistocene ice margin, distance from the late Cretaceous Sea, and vegetation type - a surrogate for productivity) were assessed using rank order statistics, especially rank order multiple regression with a backward elimination procedure. For both stygobites and troglobites, only number of caves was a significant predictor. The absence of a karst area effect suggested that the degree of karst development is better described by the number of caves rather than area of karst. There was no evidence that distance to Pleistocene glacial boundaries was important, but there was some support for the importance of distance from late Cretaceous sea margins, a potential source of aquatic subterranean colonists. Finally, there was no indication that surface productivity had an effect on species richness. Analysis was complicated by correlations among predictor variables.