Abstract
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.
Highlights
Among freshwater habitats, one of the most interesting from both a zoological and management perspective is the spring habitat
The fire salamander was detected in 24 sites, Gammarus blacanicus in 7 and N. thuringius in 17, and we observed fly larvae of the Tipulidae family in 10 sites
The first redundancy analysis (RDA) axis was represented by spring typology and the second RDA axis by the fire salamander occurrence (Figure 3; Table I)
Summary
One of the most interesting from both a zoological and management perspective is the spring habitat. Springs have since a while played a fundamental role for humans, being important for the intake of potable water. Spring habitats are defined as groundwater-dependent ecosystems (Eamus & Froend 2006) and are broadly spread worldwide. Springs can be defined as the interface between groundwaters and surface freshwater habitats (Alfaro & Wallace 1994), with both the subterranean and the epigean habitat features that interplay in characterising each spring. Zoological studies focusing on springs are often approached only under a surface perspective, neglecting the role played by groundwaters (Galassi 2001; Fiasca et al 2014). From an ecological point of view, springs have been distinguished in three main categories such as (a) flowing springs ( named rheocrenic), in which water flow feeds small streams; (b) pool springs ( named limnocrenic), where the flow is low and creates lentic habitats; and (c) seepage springs ( named helocrenic) that create a shallow damp zone (Thienemann 1922; Martin & Brunke 2012)
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