Abstract
High altitude glacier-fed streams are harsh environments inhabiting specialized invertebrate communities. Most research on biotic aspects in glacier-fed streams have focused on the simple relationship between presence/absence of species and prevailing environmental conditions, whereas functional strategies and potentials of glacial stream specialists have been hardly investigated so far. Using new and recent datasets from our investigations in the European Alps, we now demonstrate distinct functional properties of invertebrates that typically dominate glacier-fed streams and show significant relationships with declining glacier cover in alpine stream catchments. In particular, we present and argue about cause-effect relationships between glacier cover in the catchment and temperature, community structure, diversity, feeding strategies, early life development, body mass, and growth of invertebrates. By concentrating on key taxa in glacial and non-glacial alpine streams, the relevance of distinct adaptations in these functional components becomes evident. This clearly demonstrates that further studies of functional characteristics are essential for the understanding of peculiar diversity patterns, successful traits and their plasticity, evolutionary triggered species adaptions, and flexibilities.
Highlights
Freshwaters at high altitude and latitude are often strongly influenced by snow and ice cover of the catchment, resulting in temporal and spatial variabilities in environmental conditions (e.g., [1,2,3,4])
In streams with high glacial contribution, invertebrate communities were dominated by Chironomidae, for which relative abundance ranged between 71% and 98%
The lowest demand was found for Diamesinae in the coldest breeding and the invertebrate community data in sampled reaches, we found that the taxa selected for the experiments in [19] were dominant, especially in streams with high glacier cover in the catchment (Figure 3D)
Summary
Freshwaters at high altitude and latitude are often strongly influenced by snow and ice cover of the catchment, resulting in temporal (seasonal) and spatial (longitudinal) variabilities in environmental conditions (e.g., [1,2,3,4]). Glacial streams and rivers are for this reason considered as harsh ecosystems, because melting glacial ice in summer contributes significantly to the rough environmental key conditions (low water temperature, increased discharge dynamics, instable substrate and riverbed, increased turbidity and sediment load). Volume, and mass of the glacier in proportion to the catchment area, a specific degree of harshness shaping and affecting of distinct biological characteristics has typically been observed (e.g., [5,6]). Such harsh environmental conditions in glacier-fed streams and rivers have caused specific adaptations in the biological communities over evolutionary timescales. Besides the typical structural components of biodiversity, functional characteristics and patterns in glacial streams and rivers have rarely been studied (but see [9,10,11,12,13])
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