Ecosystem Birth near Melting Glaciers: A Review on the Pioneer Role of Ground-Dwelling Arthropods
by
,
Sigmund Hågvar
1,*, 
Mauro Gobbi
2
,
Rüdiger Kaufmann
3,
María Ingimarsdóttir
4,
Marco Caccianiga
5, 
Barbara Valle
5,
Paolo Pantini
6,
Pietro Paolo Fanciulli
7 and
Amber Vater
8 1
Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, 1433 Aas, Norway
2
MUSE-Museo delle Scienze, Corso del Lavoro e della Scienza, 3, I-38122 Trento, Italy
3
Department of Ecology, University Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
4
Department of Biology, Lund University, Sölvegatan 37, S-223 62 Lund, Sweden
5
Department of Biosciences, Università degli Studi di Milano, Via Giovanni Celoria 26, 20133 Milano, Italy
6
Museo Civico di Scienze Naturali “E. Caffi” di Bergamo, Piazza Cittadella 10, I-24129 Bergamo, Italy
7
Department of Life Sciences, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
8
Science and Technology Facilities Council, Polaris House, Swindon SN2 1FL, UK
*
Author to whom correspondence should be addressed.
Insects 2020, 11(9), 644; https://doi.org/10.3390/insects11090644
Submission received: 15 August 2020
/
Revised: 14 September 2020
/
Accepted: 16 September 2020
/
Published: 19 September 2020
(This article belongs to the Collection Insects in Mountain Ecosystems)
Simple Summary
Due to climate change, glaciers are retreating. On newly deglaciated ground, ecosystems gradually evolve through the process of primary succession. This gives scientists a unique opportunity to study how a new ecosystem is born. During the first few years, before plants establish, the barren ground of sand, silt, and stones close to the ice edge is conquered by a rich variety of insects, spiders, and other small animals. Many of these are predators and their prey are either transported by air or produced in situ. The real pioneers are, however, wingless springtails that graze on biofilm containing algae or cyanobacteria. Studies of two pioneer food webs showed differences in structure and function. In the one case, beetles, spiders, and harvestmen exhibit preferences for locally produced springtails, while predators in the other example relied mainly upon midges hatching from young ponds. Pioneer communities contain a mixture of generalists and specialists. Species composition vary under different climatic and geographical conditions, depending on the available candidate species in the surrounding areas. This study illustrates flexibility in the early phase of primary succession. Certain cold loving beetles, spiders, and springtails may become extinct if glaciers disappear completely.
Abstract
As glaciers retreat, their forelands represent “natural laboratories” for the study of primary succession. This review describes how certain arthropods conquer pristine ground and develop food webs before the establishment of vascular plants. Based on soil samples, pitfall traps, fallout and sticky traps, gut content studies, and some unpublished data, we compare early arthropod succession on glacial forelands of northern Europe (Iceland, Norway including Svalbard, and Sweden) and of the Alps (Austria, Italy). While macroarthropod predators like ground beetles (Coleoptera: Carabidae), harvestmen (Arachnida: Opiliones), and spiders (Arachnida: Araneae) have usually been considered as pioneers, assumed to feed on airborne prey, this review explains a different pattern. Here, we highlight that springtails (Collembola), probably feeding on biofilm made up of algae or cyanobacteria, are super-pioneers, even at high altitudes and under arctic conditions. We also point out that macroarthropod predators can use locally available prey, such as springtails or non-biting midges (Diptera: Chironomidae). Pioneer arthropod communities vary under different biogeographical and climatic conditions. Two pioneer food webs, from northern Europe and the Alps, respectively, differed in structure and function. However, certain genera and orders were common to both. Generalists and specialists live together in a pioneer community. Cold-adapted specialists are threatened by glacier melting.
Keywords:
arthropods; Collembola; food web; foreland; glacier; pioneers; succession
