Despite its inhospitable appearance and lack of any ... - Udine Cultura

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106 Hierarchical approach to the study of underground ecosystems: from large regional to small microhabitat scales Functional redundancy is a rare phenomenon in groundwater ecosystems, i.e., each trophic role is generally played by one or a few species, and there is little competition at each link of the food-chain. For the same reason, the ecosystem is certainly extremely vulnerable, as communities have low inertia (capacity for withstanding human disturbance unaltered). In fact, the extinction of one species of the community may bring the entire food-chain to a halt, with irreversible consequences for the whole ecosystem. Many underground species are therefore “key species”, as conservationist biologists call them. ■ Stygodiversity: groundwater biodiversity Groundwater in a Tuscan cave Several factors contribute towards the spatial and temporal distributions of the so-called stygodiversity, and they may be both historical (palaeoclimatic, palaeogeographical and palaeoecological events) and ecological. The structure and functioning of underground aquatic ecosystems are the result of complex processes that may act in different ways at different spatial - and temporal - levels. These factors are therefore studied at continental or regional scale (mega- or macro-scale), aquifer (meso-scale) and microhabitat level (micro- or fine-scale). These scales are a series of spatial configurations fitting one into the other, and each level integrates the processes occurring at lower levels and is associated with others at the same level. This hierarchical subdivision into continental, regional, and sometimes aquifer levels allows us to focus on the palaeogeographical and palaeoclimatic events that influenced the origin of biodiversity in groundwater. The origin of stygobionts in fresh groundwater is double. Some of them evolved from ancestors living in continental surface freshwater (lakes and rivers) - most hydrobiid gastropods, cyclopoid copepods and many canthocamptid harpacticoids, asellid isopods, niphargid amphipods and olms - and are called limnicoid stygobionts. Others - polychaetes, parvidrilid oligochaetes, amphipods of the genera Hadzia and Salentinella, microcerberid, 107
108 109 Stygodiversity in the Presciano springs: a pilot experiment Diana Maria Paola Galassi · Barbara Fiasca The Presciano springs make up one of the three great sources giving rise to the river Tirino in Abruzzi, at the foot of the greatest karstic aquifer in the Apennines. They have proved to be excellent natural laboratories for scientific research on the environmental factors affecting the spatial distribution of groundwater species (the spring area does not exceed 2000 m 2). This spring system is structurally complex, as a heterogeneous alluvial layer lies on strongly karstified bedrock, covering the underlying karstic aquifer. This situation has enabled researchers to examine how the different types of sediments affect the composition of underground communities. Detailed samplings have revealed that stygoxenic, stygophilic and stygobiont species are not at all homogenously distributed in the small spring area Presciano springs (Abruzzi) As depth increases, the relative importance of stygobionts increases to the detriment of other ecological categories, while stygophiles are generally found at intermediate depths (at 30 and 70 cm below the spring bed). This vertical distribution is a direct consequence of the ecological characteristics of stygobionts, which are morphologically and physiologically adapted to life in deep habitats, and of stygophiles, a transitional category that clearly prefers ecotonal areas. Stygoxenes are scattered, especially in subsurface sites, perhaps restricted by the low temperatures and oligotrophic conditions of the spring environment. Further analysis, carried out by dividing fauna living in karstic sites from that of alluvial sites, shows that stygophiles are almost exclusively found in the latter habitat. In addition, alluvial sites characterized by heterogeneous grain-size composition, with clearly alternating temporal upwelling and downwelling phases, host greater biodiversity, as they provide more ecological niches than karstic sites, and contain greater quantities of organic matter, which is trapped in interstices. Copepod taxocoenoses, the most important group in the analysed springs, are found in alluvial sites, with 15 out of the 17 species collected in the entire spring system. Instead, karstic sites host more monotonous karstic fauna, with one harpacticoid copepod (Nitocrella pescei) making up 90% of the entire assemblage. However, it is precisely in karstic sites that we find the most biogeographically interesting species, Pseudectinosoma reductum, a relict of ancient marine origin. Nitocrella pescei Distribution of ecological categories (number of specimens) at various depths (in cm)
Page 1 and 2: Fauna FABIO STOCH Despite its inhos
Page 3 and 4: 44 45 Methods for sampling and anal
Page 5 and 6: 48 Shells of gastropods Iglica voba
Page 7 and 8: 52 collected in phreatic waters in
Page 9 and 10: 56 ● Cyclopoid copepods. So far,
Page 11 and 12: 60 those associated with percolatin
Page 13 and 14: 64 Species of genus Niphargus; top:
Page 15 and 16: 68 ■ Decapods Italian fauna has o
Page 17 and 18: 72 Stygofaunal provinces in Italy T
Page 19 and 20: 76 aquifers in the Sabini mountains
Page 21 and 22: 80 ■ The ecology of aquifers Acco
Page 23 and 24: 84 85 The discovery of a new submer
Page 25 and 26: 88 anastomoses, often adjacent to t
Page 27 and 28: 92 93 The saline springs of Poiano:
Page 29 and 30: 96 Modified sensory setae on the an
Page 31 and 32: 100 Theoretical evolutionary sequen
Page 33: 104 Sketch showing degrading phases
Page 37: 112 animal groups still living on t

Despite its inhospitable appearance and lack of any ... - Udine Cultura

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