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, andMother Lode – are described and compared. The number of aquatic(stygobitic) species ranged from zero (Black Hills) to 82 (Appalachians), andthe number of terrestrial (troglobitic) species ranged from zero (Florida LimeSinks) to 256 (Interior Low Plateau). Even at the level of genus, overlapbetween regions is low. Several predictor variables (karst area, number ofcaves, number of long caves, number of deep caves, distance from the Pleistoceneice margin, distance from the late Cretaceous Sea, and vegetation type – asurrogate 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 significantpredictor. The absence of a karst area effect suggested that the degree of karstdevelopment is better described by the number of caves rather than area ofkarst. There was no evidence that distance to Pleistocene glacial boundaries wasimportant, 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 speciesrichness. Analysis was complicated by correlations among predictor variables