Use and misuse of the term ‘glacial relict’ in the Central European biogeography and conservation ecology of insects

Abstract

We argue that the term 'glacial relict' is often misused in Central European biogeography and conservation ecology to refer to tyrphobiotic insect species which occur in peat bogs. There is no evidence to argue that these insect populations represent remnants dating back to the Pleistocene glacial stages. Instead, these insect species are mainly associated with colder local climate, special edaphic conditions, and the specific plant composition of the bogs. Therefore bogs are isolated habitats for cold-adapted, tyrphobiotic species, in which they have persisted since the early or middle Holocene, and the conservation of the bogs is critically important for the future survival of the boreo-alpine insect species in Central Europe.

The distribution pattern of mire specialist butterflies in raised bogs of the northern lowlands of Central Europe

“…However, as there is no obligatory connection between these species and Pleniglacial or Late Glacial environments (Sommer et al 2015), we suggest following Spitzer et al (1999) and Spitzer and Danks (2006) in classifying peat bogs with cold adapted and tyrphobiontic insect species as "palaeorefugia" which indicate the colonization origin of this species and establishment of populations during past millennia of the Holocene. In this sense the butterfly Boloria aquilonaris and dragonfly Aeshna subarctica are typical cold-adapted species; isolated relict survivors in peat bog palaeorefugia (Sommer et al 2015). As documented, in northern Germany, during the 19 th and 20 th centuries peatlands and raised bogs were increasingly degraded and drained by humans (Joosten and Couwenberg 2001;Heinecke et al 2011;.…”

“…In Central Europe these species show a strong association with peat bogs. Several of these species, for example B. eunomia or C. palaeno appear to have relict distributions, restricted to palaeorefugia in Central and Northern Europe (Nève et al 2009;Krzysztofiak et al 2010;Turlure 2010;Sommer et al 2015). The Bog Fritillary B. eunomia is not restricted to raised bogs but also inhabits pine bogs, fens and marshes and the ecotone regions between bogs and fens (Nève et al 2009;Noreika et al 2016;Sielezniew et al 2019).…”

“…The term "glacial relicts" is frequently used for boreo-montane species from peat bogs, especially by lepidopterists (Turlure et al 2009(Turlure et al , 2010. However, as there is no obligatory connection between these species and Pleniglacial or Late Glacial environments (Sommer et al 2015), we suggest following Spitzer et al (1999) and Spitzer and Danks (2006) in classifying peat bogs with cold adapted and tyrphobiontic insect species as "palaeorefugia" which indicate the colonization origin of this species and establishment of populations during past millennia of the Holocene. In this sense the butterfly Boloria aquilonaris and dragonfly Aeshna subarctica are typical cold-adapted species; isolated relict survivors in peat bog palaeorefugia (Sommer et al 2015).…”

“…Recently, in light of numerous scientific studies regarding the role and function of peatlands in the global carbon and water cycles (e. g. Dorrepaal 2009;Kasimir et al 2018 and references therein), there have been increased bog restoration efforts in many European countries; many of which have been supported by the European Union (Bonn et al 2016). From a biogeographical point of view, raised bogs in Central Europe provide refugia for boreo-alpine species in a large scale temperate landscape and support the habitat preference of boreal or subarctic species mainly by climatic (cold) and edaphic (acidic and nutrient poor) conditions (Spitzer and Danks 2006;Sommer et al 2015). During the climatic development from the Early to Late Holocene peat bogs remained "cold-lands" within the temperate biome and established patchy and isolated refugial habitats for cold adapted biota (Spitzer and Danks 2006;Sommer et al 2015).…”

“…From a biogeographical point of view, raised bogs in Central Europe provide refugia for boreo-alpine species in a large scale temperate landscape and support the habitat preference of boreal or subarctic species mainly by climatic (cold) and edaphic (acidic and nutrient poor) conditions (Spitzer and Danks 2006;Sommer et al 2015). During the climatic development from the Early to Late Holocene peat bogs remained "cold-lands" within the temperate biome and established patchy and isolated refugial habitats for cold adapted biota (Spitzer and Danks 2006;Sommer et al 2015). The term "glacial relicts" is frequently used for boreo-montane species from peat bogs, especially by lepidopterists (Turlure et al 2009(Turlure et al , 2010.…”