ABSTRACT
Subterranean ecosystems pose special problems for conservation due to their intrinsic fragility and the distinctive features of subterranean communities, including a high degree of endemism and morphological, ecological and behavioral specialization. Such fragility is a consequence of the relatively low biological diversity of subterranean ecosystems and their general dependence on nutrients imported from the surface, making them strongly infl uenced by disturbances in epigean habitats. Furthermore, many troglobites have small geographic ranges and low population densities, resulting in small population sizes, K-selected life histories, thus population turnover is slow and their ability to recover from population losses is decreased compared to epigean related taxa, and they may be highly susceptible to environmental fl uctuations (Trajano 2000). Around 98% of unfrozen freshwater in the world is subterranean and Juberthie (2004) claims at least 50% is inhabited by troglobitic and troglophilic species. These aquatic habitats include karst aquifers (including the epikarst zone), phreatic aquifers in valleys in many kinds of sediments and rocks, interstitial and hyporheic habitats, and base-level streams. Troglobitic fi shes have been found in all these kinds of habitats (see, for instance, Trajano and Bichuette, this volume).
