An overview of the cave and interstitial biota of Croatia

The karst areas in Croatia, part of the Dinarides, have been defined biospeleologically as an -ea of high biodiversity in world terms, covering 26 thousand km2 in all. In this monograph we ; :ue data about the biodiversity of subterranean habitats and their biota primarily from a taxo ~mic perspective with special attention being paid to regional diversity. The diversified geomor-:~.ology, hydrology and climate have resulted in a remarkable range of different underground hab:• , in Croatia, viz. inland and coastal caves, superficial and deep phreatic networks, interstitial ~ orheic substrates and other infiltration zones, etc. In Croatia more than 500 obligate subterra_an species and subspecies are known from caves and interstitial habitats. The majority of subter:• .~an species in Croatia are terrestrial biota. There are 299 troglobiont and 170 stygobiont taxa ~~ wies and subspecies) recorded. Most subterranean species have very restricted ranges, almost 70% of them endemic to Croatia. Cave fungi are poorly known. Among them there are several important parasitic troglobionts and troglophilic species on cave coleopterans and troglophilic moths in Croatian caves. Some saprotrophic species could be troglobiotic too but their taxonomic and/or ecological status must be clarified in future research. 4Vith a respect to the number of troglobionts, the five largest animal groups are Coleoptera, Pseudoscorpiones, Araneae, Gastropoda and Diplopoda. The beetles (Coleoptera) are predominant. More than 100 cavernicolous beetles (species and subspecies) are known in Croatia. Among stygobionts, the Crustacea predominate. At least half of species described are Crustacea. Among Crustacea, the orders Syncarida and Thermosbaenacea are exclusively stygobiotic. Numerically, among crustacean stygobiotic Amphipoda dominate in caves and Copepoda in interstitial habitats. The only known stygobiotic sponge Eunayius subterraneus Sket et Velikonja inhabits several caves in Croatia. Also, the only known stygobiotic clam Congeria kusceri Bole inhabits a series of caves in Croatia. Other important groups include hydrozoa, planarians (Temnocephalida and Tricladida), snails (Mollusca: Gastropoda) and the only European stygobiotic Chordata Proteus anguinus Laurenti. The high taxonomic diversity of the subterranean biota of Croatia can be attributed partly to the geographical heterogeneity and a rather unique combination of various geological and ecological phenomena.