Environmental classification of springs of the Italian Alps and its consistency across multiple taxonomic groups

The traditional and widely used ecomorphological spring classification—pool springs (limnocrenes), seepages (helocrenes), and flowing springs (rheocrenes)—is based mainly on the flow regime at the spring mouth. This clear distinction is based purely on environmental conditions, but how and to what extent these spring typologies are reflected by biological assemblages consisting of different taxonomic groups remains largely untested. Classification of habitats typically is based on one or few taxonomic groups. However, groups are likely to differ in their response to the environment, so different, equally valid classifications might result with different groups. We evaluated the responses and their congruence of a wide range of taxonomic groups to different spring types. Eighty-six springs in the Italian Alps were first classified based on environmental factors only. The consistency of this classification was tested using diatoms, bryophytes, vascular plants, nematodes, mollusks, oligochaetes, water mites, copepods, ostracods, chironomids, stoneflies, and caddisflies. When only environmental variables were used, 7 spring types were distinguished: limnocrenes and helocrenes, low- and high-altitude rheocrenes on carbonate rocks, rheocrenes on siliceous rocks, rheocrenes with high discharge, and hygropetric rheocrenes. This classification was reflected by most taxonomic groups, and many species were characteristic for §1 spring type. However, the predictive power of the environment for determining species distribution was generally low, a result suggesting that other factors may play an important role in structuring spring assemblages. Concordance among taxonomic groups was found for 2 macrogroups of organisms: autotrophs (diatoms, bryophytes, and vascular plants) and heterotrophs. This result shows that achieving a general classification of springs relevant across all taxonomic groups would be difficult.