Regional species richness in an obligate subterranean dwelling fauna – epikarst copepods

Aim  The diversity of the obligate cave-dwelling fauna has proved difficult to measure because of the highly localized distributions of most species. We investigated: (1) the local and regional diversity patterns of a major component of the obligate cave-dwelling fauna living in the epikarst zone, the karst layer closest to the surface; (2) variations in local and regional patterns of species richness; and (3) sampling sufficiency at multiple scales.
Location  Caves in the Dinaric Mountains of Slovenia.
Methods  We sampled continuously the abundance of 37 species of copepods dislodged from the epikarst from 35 ceiling drips in six caves for a period of one year. Copepods were collected in a specially designed net that allowed continuous collection.
Results  Based on species accumulation curves and Chao estimates of total diversity, we determined that 3–4 months of continuous sampling were sufficient to find 90% of the species in a drip, that five drips were sufficient to find 90% of the species in a cave, and that five caves were sufficient to find 90% of the species in a region.
Main conclusions  The epikarst copepod fauna is a significant part of the aquatic cave fauna, contributing about 20% at the regional level. Because of the scale of variation, much of which occurs within a cave, and because of the availability of continuous sampling devices, the epikarst component of subterranean diversity seems to be more thoroughly and accurately measured than do other components.