Think of what lies below, not only of what is visible above, or : a comprehensive zoological study of invertebrate communities of spring habitats

Springs are interface habitats between the surface and subterranean environments, often neglected by zoological studies and generally regarded only from a surface perspective. Springs are also often collected and managed by humans: catching buildings that collect spring water may provide an accessible window over groundwaters. With this paper, we aim to assess the determinants of invertebrates’ occurrence in springs using a comprehensive approach and considering the role of catching buildings and of predator occurrence. During 2017 and 2018, we performed six repeated surveys in 44 springs of N-Italy. We distinguished between collected and natural springs, assessed the springs morphological features and recorded the occurrence of predator Salamandra salamandra (Linnaeus, 1758) larvae and of four invertebrate taxa corresponding to strictly spring-dwelling, groundwater-dwelling and stream-dwelling groups, such as the gastropod Graziana alpestris (Frauenfeld, 1863), the amphipods Niphargus thuringius Schellenberg, 1934 and Gammarus balcanicus Schäferna, 1922 and dipterans larvae of the family Tipulidae. We used a constrained redundancy analysis to evaluate the relative role of fire salamander occurrence and of springs features on the occurrence of the invertebrate taxa surveyed. Spring typology and fire salamander larvae were the major determinants of spring invertebrates’ occurrence. G. alpestris was positively related to artificial catching structures. Fire salamander was related to the occurrence of N. thuringius, G. balcanicus and Tipulidae larvae. Our results provide evidence that catching spring structures can significantly favour the detection of strictly spring-dwelling species; moreover, we reveal that the breeding of semi-aquatic predators like salamanders may play important roles on the community of invertebrates occurring in the spring habitats.