Distribution and evolution of Florida's troglobitic crayfishes

Abstract

The current knowledge of Florida's troglobitic crayfish fauna is discussed, interpretations of distributional and ecological patterns are reviewed, and an explanation of their evolutionary history is attempted. These crayfishes are restricted to certain geological formations that have light to nonexistent elastic overburdens. Areas with moderate to heavy accumulations over the carbonate rocks lack these crustaceans. The Crystal River Formation, a group of highly soluble Eocene Iimestones, is the most important geological element influencing the distribution of most Florida cave-dwelling crayfishes. Members of the Procambarus lucifugus complex (with the possible exception of an undescribed species from Lake County), Procambarus pallidus, Troglocambarus maclanei, and Cambarus cryptodytes, are apparently confined to this formation. The remaining species are confined to other limestones (Procambarus acherontis and Procambarus species from Lake County in the Hawthorne Formation, Procambarus milleri in the Miami Oolite, Procambarus horsti and Procambarus orcinus in the St. Marks Formation). Field observations suggest that available sources of food energy dictate which species groups inhabit particular cave systems. Species complexes that are most restricted to environments which provide large accumulations of organic detritus become ecologically and geographically isolated from other populations and exhibit increased speciation. For example, members of the Procambarus lucifugus complex seem to have demanding energy budgets and occur only in localized karst areas exhibiting mature features and high energy input. Dependency on constant energy supplies provided by large sinkhole entrances and/or bat roosts probably limits their dispersal ability. In contrast, members of the Procambarus pallidus complex inhabit systems with limited energy inputs, such as springs and sinkholes with small openings. Troglocambarus maclanei occurs syntopically with members of the Procambarus lucifugus and Procambarus pallidus complexes and may be capable of interstital movements from one cave to another. This may help to explain its extensive distribution.