The groundwater fauna of Piani Eterni karstic area (Dolomiti Bellunesi National Park, Southern Limestone Alps, Italy) and its zoogeographic significance

the groundwater fauna of the Piani Eterni karstic area was surveyed in 2004-2007. Piani Eterni is a 14 km2 karstic plateau, ranging from 1700 to 1900 m a.s.l., located inside a national Park (dolomiti Bellunesi) in the Southern limestone Alps. the Piani Eterni complex is the largest and deepest cave system in the dolomites and currently includes over 17 km path length, with a maximum depth of 971 m below the surface. the groundwater fauna, collected from pools, rivulets and small lakes in the vadose zone of Piani Eterni complex and the nearby Isabella cave includes 27 species (11 nematoda, 7 Annelida, 7 crustacea and 2 diptera). Ten species are stygobionts, and five of them are new to Science. The importance of Diptera in this subterranean karstic system is noteworthy; several larvae of the chironomid Eukiefferiella gracei group were found both in groundwater bodies of Piani Eterni complex and in a spring (Fontanon) which likely drains part of the aquifer, suggesting that this stygoxene chironomid may be considered as a “biological tracer”. Some other stygoxene species (most of nematoda and Annelida and some copepoda) live in wet soil, mosses, and interstitial habitats as well as in some surface environments; they are probably recent (i.e. post-glacial) colonizers of the cave system. the presence of stygobionts (37% of the fauna) in an area completely covered by the Alpine glaciers during Pleistocene is noteworthy. the presence of a possible relict fauna in this area may be explained either by a re-colonization following the retreat of Wurmian glaciers, or by their survival in the deep groundwater aquifer during the Quaternary glaciations. Finally, the observed habitat segregation of subterranean species within the caves studied, together with a narrow range of variation of water chemistry, indicating a homogeneity of physico-chemical parameters, suggests that habitat complexity may have played a major role, together with historical factors, in shaping the groundwater biodiversity in this cold, oligotrophic cave system.