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The distribution pattern of relict and specialised species in calcareous fens was revealed to be non-stochastic, with ancient fens harbouring more of these species than younger ones. This phenomenon could be caused by long-lasting in situ survivals over millennia, but direct palaeoecological evidence is lacking. We addressed the question whether at least some ancient calcareous fens indeed retained open-fen patches throughout the Holocene, using a palaeoecological approach involving proxies with different taphonomies (pollen, vascular plants, bryophytes, molluscs). We identified three old fens in the Western Carpathians, where several postglacial relict species have recently been found, and we reconstructed their histories with respect to sedimentary processes, vegetation structure and dynamics of relict species. The development at all the sites started with a (semi)-open fen community dominated by sedges and brown mosses. The site with the highest recent number of relict species was reconstructed to harbour open patches continually since the late Glacial to the present, including the middle Holocene when open-fen patches were restricted. By contrast, at the site with the lowest recent number of relict species, a large sedimentary hiatus suggested peat mineralisation or erosion that prevented the survival of light-demanding species. At all the sites, characteristic snails of European Glacial periods occurred during fen initiation, but disappeared around the early/middle Holocene transition. The probability of a relict species being present in a modern fen community increases with fen age, but it also depends on the continual existence of open-fen patches and peat accumulation throughout the middle Holocene.
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The Holocene
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DOI: 10.1177/0959683614566251
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Introduction
Understanding and predicting biodiversity loss is one of the most
serious problems in current ecology. Palaeoecology may contrib-
ute to this question by providing data about the rate and spatial
dynamics of extinctions, survivals and coexistences by studying
the fossil record containing evidence of rapid climate changes
over long time scales (Seddon et al., 2014). Unfortunately, ecol-
ogy and Quaternary palaeoecology have largely developed as par-
allel disciplines, and only a few palaeoecological studies have
addressed ecological questions or focussed on dynamics of non-
woody species. Closing the gap between ecology and Quaternary
palaeoecology is an important and topical challenge for ecologists
and palaeoecologists (Reitalu et al., 2014; Seddon et al., 2014).
One long-standing question at the interface between ecology and
Quaternary palaeoecology is, ‘Why are some boreal and conti-
nental plant and animal species, many of which are highly endan-
gered, so unpredictably scattered across temperate fens?’.
Ancient calcareous fens are fascinating ecosystems acting as
refugia for many highly specialised species (Hájek et al., 2011;
Wassen et al., 2005). In the temperate zone, they harbour a suite
of species that display an island-like scattered distribution and
that are recently critically endangered (e.g. Hampe and Jump,
2011; Schenková and Horsák, 2013). Since the beginning of
biogeography in Central Europe, these species have been
considered relicts of the cold past and were therefore called gla-
cial relicts (Holmquist, 1962; Rybníček, 1966); the term corre-
sponds to the terms postglacial relicts, relicts since postglacial
times and cold-stage relicts, which have been used more recently
(Hájek et al., 2011). The relict concept (Holmquist, 1962) was
very popular in the descriptive phase of Central and Southern
European field botany and zoology, but later, it was abandoned
by mainstream science because of the difficulties of obtaining
unequivocal evidence of relict distribution patterns of some spe-
cies. However, this concept has been persisting, mostly in the
world of local studies, local nature conservancy and enthusiastic
Using multi-proxy palaeoecology to test
a relict status of refugial populations of
calcareous-fen species in the Western
Carpathians
Petra Hájková,1,2 Michal Horsák,2 Michal Hájek,1,2 Vlasta
Jankovská,1,2 Eva Jamrichová1,2 and Jitka Moutelíková2
Abstract
The distribution pattern of relict and specialised species in calcareous fens was revealed to be non-stochastic, with ancient fens harbouring more of
these species than younger ones. This phenomenon could be caused by long-lasting in situ survivals over millennia, but direct palaeoecological evidence
is lacking. We addressed the question whether at least some ancient calcareous fens indeed retained open-fen patches throughout the Holocene, using a
palaeoecological approach involving proxies with different taphonomies (pollen, vascular plants, bryophytes, molluscs). We identified three old fens in the
Western Carpathians, where several postglacial relict species have recently been found, and we reconstructed their histories with respect to sedimentary
processes, vegetation structure and dynamics of relict species. The development at all the sites started with a (semi)-open fen community dominated by
sedges and brown mosses. The site with the highest recent number of relict species was reconstructed to harbour open patches continually since the
late Glacial to the present, including the middle Holocene when open-fen patches were restricted. By contrast, at the site with the lowest recent number
of relict species, a large sedimentary hiatus suggested peat mineralisation or erosion that prevented the survival of light-demanding species. At all the
sites, characteristic snails of European Glacial periods occurred during fen initiation, but disappeared around the early/middle Holocene transition. The
probability of a relict species being present in a modern fen community increases with fen age, but it also depends on the continual existence of open-fen
patches and peat accumulation throughout the middle Holocene.
Keywords
biodiversity, calcareous fen, climate, fossil record, Holocene extinction, Western Carpathians
Received 18 July 2014; revised manuscript accepted 5 December 2014
1 Department of Vegetation Ecology, Institute of Botany, Academy of
Sciences of the Czech Republic, Czech Republic
2
Department of Botany and Zoology, Faculty of Science, Masaryk
University, Czech Republic
Corresponding author:
Petra Hájková, Department of Botany and Zoology, Faculty of Science,
Masaryk University, Kotlářská 2, CZ-61137 Brno, Czech Republic.
Email: buriana@sci.muni.cz
566251HOL0010.1177/0959683614566251The HoloceneHájková et al.
research-article2014
Research paper
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2 The Holocene
nature lovers. The revisiting of the relict concept was triggered
by the development of phylogeographic methods (e.g. Reisch
et al., 2003; Vogler and Reisch, 2013), although even in this
field, the cold-loving postglacial relicts still stay in the shadow
of true glacial relicts (from the phylogeographic perspective),
i.e., the warmth-demanding species that survived the Full Gla-
cial period in small pockets with favourable mesoclimate condi-
tions (e.g. Stewart et al., 2010).
In our previous study (Hájek et al., 2011), we started to revit-
alise the concept of postglacial relicts for the archipelago of cal-
careous fens in the Western Carpathians (Central Eastern Europe,
Slovakia). In that study, we dated 47 recently well-preserved cal-
careous fens and demonstrated statistically that a suite of plant
and mollusc species was significantly linked to old fens at the
millennial scale, independent of the effect of recent fen area. High
age of a fen site determines the occurrence of those species that
are indeed rare, endangered and unevenly distributed in temperate
Europe (Horsák et al., 2012). Although this result brought certain
evidence for the validity of the relict concept for the archipelago
of Central European calcareous fens, some questions remained
unresolved. We observed certain differences in stratigraphy
among particular ancient fens. Some of them contained phases
rich in wood remains, while others seemed to be continuously
open, but detailed sequential palaeoecological analyses were not
performed (Hájek et al., 2011). Particular sequences contained
different species at their bottom, and some of them contained
snail indicators of glacial landscapes (Hájková et al., 2012b).
In addition, our other studies have suggested that the recent
plant and snail communities of young fens have been assembled
predominantly during the Wallachian colonisation taking place
from 14th to 17th centuries (Hájková et al., 2012b; Jamrichová
et al., 2013). It was a large colonisation wave from the eastern
part of the Carpathians to the west, which completely changed so
far poorly settled mountain landscapes. The large areas were
deforested for the pastoral purposes, forest springs were opened
as well, and many new spring-fens have originated on the land-
slides. Thus, we cannot reject the assumption that such a huge
landscape transformation also altered somehow the ancient fen
biota. Hence, it is unrealistic to suppose that relict assemblages
of ancient fens are completely the same as those that occurred in
the late Glacial or early Holocene. Furthermore, we still have not
obtained a coherent set of evidence for continuous in situ sur-
vival of light-demanding fen species during the middle Holocene
forest optimum in the Western Carpathian Mountains. Scattered
data came from some undated snail sequences (Ložek, 1964) and
for Cladium mariscus in one hot spring lowland fen (Hájková
et al., 2013).
For a more thorough understanding of the dynamics of rare,
relict fen species in temperate landscapes, it is therefore necessary
to focus in more detail on the most representative fen peat
sequences and to reconstruct their history using identifications of
their fossils. In minerotrophic soligeneous fens, however, this
approach does not always bring sufficient evidence supporting or
rejecting the hypotheses about continual Holocene survival. Fen
sequences often contain intervals where either pollen microfossils
or plant macrofossils (determinable to species level) were not pre-
served in sufficient numbers. Nevertheless, our previous studies
(Hájková et al., 2012b; Jamrichová et al., 2013) have demon-
strated that the combination of fossils with different taphonomic
modes (pollen, snail shells and plant macrofossils) leads to more
direct and more interpretable evidence of environmental changes
in the Holocene. We therefore applied this multi-proxy approach
to all three recently known well-preserved fens in the intermoun-
tain basins of the Inner Western Carpathians, which have at least
four important site characteristics in common: (1) they are old,
with peat initiation in either the late Glacial or at the onset of the
Holocene; (2) they favour fossilisation of both snail and plant
remains; (3) they harbour postglacial relicts (tested successfully
by Hájek et al., 2011) in recent assemblages; and (4) they contain
characteristic species of glacial landscapes in the bottom layers
(data from Hájková et al., 2012b).
From these three fens, we took sequences of their deposits in
order to address the following questions: (1) did open, treeless fen
patches persist in these fens during the entire Holocene? If there
are differences in their extent and continuity in particular profiles,
do they correspond to the level of extinction at a site and to a
present-day representation of relict species? (2) Is it possible to
find a threshold when the species characteristic of glacial land-
scapes became extinct? (3) To what extent do the present-day fen
assemblages correspond to ancient ones and how did the late
Holocene Wallachian colonisation affect them? (4) If the late Gla-
cial assemblages differ, are they at least partially analogous to the
present-day assemblages in boreal or continental landscapes? and
(5) Which macroclimatic conditions could be reconstructed for
the late Glacial stadial in the Inner Carpathian basins based on the
past occurrences of snail species?
Materials and methods
Characteristic of the study sites and field sampling
The three preserved fen sites that fulfilled our pre-selection crite-
ria are located close to each other, in the intermountain basins of
north-eastern Slovakia (Figure 1), namely in the Poprad Basin
(Hozelec – HOZ), at the margin of the Ľubovňa Basin (Valalská
voda – VAL) and in the Liptov Basin (Brezové – BRE). The
study sites are located in the montane belt in altitudes of
677 m.a.s.l. (HOZ), 714 m.a.s.l. (VAL) and 894 m.a.s.l. (BRE).
All these sites can be classified as calcareous spring-fens sup-
plied by an alkaline mineral-rich groundwater (pH 7–7.8; water
conductivity varied from 360 µS cm–1 in BRE to 918 µS cm–1 in
HOZ). Vegetation growing in all study sites belongs to the asso-
ciation Caricetum davallianae Dutoit 1924 (for more informa-
tion about floristic composition, see Dítě and Pukajová, 2004 and
Hájek et al., 2006). Snail assemblages are species-rich and
include several threatened wetland specialists and relict species
(for a complete species composition of recent assemblages, see
Appendix S3, available online). The sites differ in their recent
size. The Brezové is the largest fen out of the study sites today
(about 11.500 m2), Valalská voda is smaller (ca. 1900 m2) and
Hozelec is the smallest one with only ca. 60 m2; however, this
site was a part of a large fen complex in the past being destroyed
by human activities. All sites represent remnants of large fen
complexes, and therefore they are protected and managed by
nature conservancy. The regular mowing prevents overgrowing
by trees and supports well-developed bryophyte layer with many
relict species. Without this management, probably only the wet-
test places with spring pools would remain open.
These sites differ in numbers of postglacial relict species
(Table 1), with the lowest in the Valalská voda fen and the highest
in the Hozelec fen. There are mostly species strongly specialised
to calcareous fens with a preserved hydrological regime, i.e., sta-
ble water level around the surface for almost the whole year (e.g.
plants Campylium elodes, Carex dioica, Primula farinosa and
Triglochin maritima; snails Euconulus praticola, Pupilla alpicola
and Vertigo geyeri). Some relict species display wider ecological
niche occurring also in the moderately rich fens with lower
amount of calcium in groundwater (Drepanocladus trifarius,
Carex diandra and Hamatocaulis vernicosus). All relict species
are related to open habitats and are not able to survive in a close
canopy. Also the increase in nutrient supply can be detrimental for
these species because they are competitively poor and enhanced
amount of nutrients promotes competitively strong tall-herb vas-
cular plants and ubiquitous grassland bryophytes such as Callier-
gonella cuspidata (Hájek et al., 2014).
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Hájková et al. 3
At Valalská voda and Hozelec, we sampled a single peat pro-
file from an open excavation. Peat for mollusc analyses was sam-
pled separately to obtain sufficient volume of material. Peat for
macrofossil and pollen analyses was stored in metal boxes
(50 cm × 10 cm × 10 cm). At the Brezové fen, we sampled two pro-
files: one in a place with extremely high calcium carbonate pre-
cipitation today and another in a place with shallow pools with
less calcium carbonate precipitated. The first profile was obtained
using a percussion drilling set because of difficulties with manual
drilling. In order to obtain enough material for mollusc analysis,
we took three parallel cores located close to each other (BRE-A1,
BRE-A2 and BRE-A3). The second peat profile was sampled
from an open excavation to metal boxes (BRE-box). For more
details about peat composition, see Appendix S1, available online.
Radiocarbon dating
Macrofossils of chosen samples were radiocarbon-dated at the Cen-
ter for Applied Isotope Studies, University of Georgia, Athens, USA
(for details, see Table 2). We have strictly chosen seeds of terrestrial
plants (mostly Carex seeds) and terrestrial bryophytes (Tomentyp-
num nitens and Bryum pseudotriquetrum) to avoid the hard-water
error (Grimm et al., 2009). At the Hozelec site, some layers did not
contain suitable macrofossils for dating; therefore, we had to use the
bulk for the dating. The bulk dates appear reliable as they fit existing
knowledge on vegetation development in the region (Jankovská,
1988). Possible biases caused by the bulk dating cannot alter our
main result on vegetation succession at the Holocene scale. Bulk
samples were analysed at the Centre for Isotope Research, Univer-
sity of Groningen, the Netherlands. Data were calibrated using the
IntCal13 calibration curve (Reimer et al., 2013) with OxCal4 soft-
ware version 4.2 (Bronk Ramsey, 2009), and the middle value of the
calibrated 2σ range (before the year 1950) was used.
Laboratory analyses
Each sample for plant macrofossil analysis (volume of 100 cm3) was
sieved into three fractions (>1 mm, 1–0.63 mm and 0.63–0.20 mm).
Figure 1. Map of the study area.
Table 1. Characteristics of studied calcareous fens: Hozelec (49.045278N/20.334167E; 677 m.a.s.l.), Brezové (49.050833N/20.028333E;
891 m.a.s.l.) and Valalská voda (49.205N/20.786389E; 714 m.a.s.l.) and the number of relict species recently occurring in a site. The first number
refers to the number of calcareous fen relicts predicted by null model (Hájek etal. 2011), and the second one to the number of arbitrary
assessed relicts (the species, which are not obligate calcareous-fen specialists and hence they were not tested in Hájek etal. 2011).
Locality Number of relict species Particular relict species
Bryo Vasc Snails Total
Hozelec (HOZ) 0/+1 2/+2 2/+2 4/+5 Primula farinosa, Triglochin maritima, Pupilla alpicola, Vertigo geyeri/ + Campylium
elodes, Carex diandra, C. dioica, Euconulus praticola, Pseudotrichia rubiginosa
Brezové (BRE) 0/+1 3/+0 1/+1 4/+2 C. dioica, P. farinosa, T. maritima, V. geyeri/ + Drepanocladus trifarius (=Pseudocal-
liergon trifarium), E. praticola
Valalská voda (VAL) 0/+1 0/+0 1/+1 1/+2 V. geyeri/ + Hamatocaulis (Drepanocladus) vernicosus, E. praticola
Bryo: bryophytes; vasc: vascular plants.
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4 The Holocene
The larger fractions were analysed using a stereomicroscope. A
quantity of 1 mL of the finest fraction was examined at 100×–400×
magnification in order to identify small seeds (e.g. Juncus spp.) or
oogonia of Characeae. The material for pollen analyses was sub-
sampled (volume of 1 cm3) at 10 cm (VAL, BRE-box) or 5 cm
(HOZ) intervals along the profile and processed using standard tech-
niques (Fægri and Iversen, 1989). Samples containing clastic mate-
rial were pre-treated with cold concentrated hydrogen fluoride for
24 h and then potassium hydroxide solution before acetolysis. At
least 300 pollen grains of terrestrial plants per sample were identi-
fied (HOZ profile). Because of low quantities of palynomorphs in
VAL and BRE profiles, at least three microscopic slides were
counted for each sample. Fossil mollusc shells in BRE-A1 and
BRE-box were extracted from the same samples (volume of
100 cm3) as macrofossils, and in the VAL and HOZ, the molluscs
were sampled separately (the approximate volume 500 cm3). Mollusc
shells were obtained from recent surface samples by carefully wash-
ing each sample (12 L of bryophytes and litter) in a bowl-shaped
sieve (mesh size 0.5 mm) to remove fine soil (see Horsák, 2003).
After drying, the shells were separated from the remaining material.
See Appendices S2–S4, available online, in Supporting Material for
the list of all identification literature. All presented diagrams were
created using C2 software (Juggins, 2003). The nomenclature fol-
lows Beug (2004) for pollen, Marhold and Hindák (1998) for vascu-
lar plants, Kučera et al. (2012) for bryophytes and Horsák et al.
(2013) for molluscs. In the paper, we use the modern simplified
division of the Holocene: early Holocene (11,700–8200 cal. yr
BP), middle Holocene (8200–4200 cal. yr BP) and late Holocene
(4200 cal. yr BP–AD 2000). P Hájková identified macrofossils in all
profiles, M Horsák snails in Hozelec and Valalská voda profiles, J
Moutelíková snails in profiles from the Brezové fen, E Jamrichová
pollen in Hozelec profile and V Jankovská pollen in Valalská voda
and Brezové profiles.
Other analyses
Several recent studies have shown that southern Siberian moun-
tain ranges harbour biotas that act as the best modern analogies of
those reconstructed for full-glacial Central Europe (e.g. Kuneš
et al., 2008; Pavelková Řičánková et al., 2014). This was also
confirmed by our malacological research in the Altai Mountains
(e.g. Horsák et al., 2010). Here, we used macroclimate character-
istics of 34 Altaian sites with the presence of four characteristic
glacial snail species that were found in the bottom layers of the
studied fen deposits. For details about the sampling of modern
snails in 2005–2006 and 2011 and the obtaining of climatic data,
see Horsák et al. (2010).
Results
For the complete information about species composition of fossil
assemblages, see Figures 2–5 (showing synoptic palaeoecological
diagrams with the selected taxa and ecological groups of taxa)
and Appendices S2 (pollen), S3 (molluscs), S4 (macrofossils) and
S5 (ecological groups), available online for full data.
Development of the landscape context
On the basis of pollen analysis (see Figures 2–4 and Appendix S2,
available online), the late Glacial landscape was reconstructed to
be covered by hemiboreal forests in the mosaic of tundra and
steppe habitats. Forests were mainly composed of Larix (domi-
nant), Pinus cembra, P. sylvestris/mugo (dominant), Betula
pendula/pubescens and Picea abies, which probably occurred in
humid and microclimatically favourable places. However, the
studied sites differed in the abundance of individual tree taxa. Pol-
len of Larix decidua/sibirica (Larix type) showed the highest
abundance around the Valalská voda fen, whereas the representa-
tion of P. cembra was the highest at the Hozelec site and the spe-
cies was almost absent at the Valalská voda site. Sorbus aucuparia
was locally present with a low abundance (VAL). The understorey
was composed of, for example, Polygonatum verticillatum, Vale-
riana cf. tripteris (pollen type V. montana) and cf. Scilla bifolia/
kladnii (the Scilla type). The two former species nowadays occur
in mountain coniferous forests, but the latter species occurs in
either deciduous or alluvial forests (its occurrence in open hemi-
boreal forests of the late Glacial cannot be excluded). Treeless
vegetation consisted of steppe–tundra species such as Artemisia
Table 2. Results of 14C dating from studied peat profiles. The presented ages are middle values and intervals of calibrated 2σ range BP.
Samples Depth (cm) Dating method Age in uncal. yr BP Cal. yr BP (interval) Cal. yr BP (median) Material
Brezové
A1 drill
UG-11635 40–45 AMS 120 ± 25 11–270 115 Seeds
UG-11636 225–230 AMS 9.930 ± 30 11,241–11,590 11,312 Bryophytes
Excavated pit
UG-7599 41–43 AMS 150 ± 25 0–284 173 Seeds
UG-17159 78–80 AMS 1980 ± 25 1880–1990 1928 Seeds
UG-17160 138–140 AMS 3930 ± 30 4249–4507 4366 Seeds
UG-7600 184–189 AMS 7360 ± 30 8042–8306 8178 Seeds
Valalská voda
UG-8797 21–24 AMS 300 ± 30 296–461 386 Seeds
UG-8798 24–27 AMS 480 ± 20 504–535 518 Seeds
UG-10018 47–48 AMS 8320 ± 40 9145–9464 9349 Seeds
UG-10020 90–93 AMS 11,530 ± 35 13,289–13,450 13,371 Bark
UG-7603 136–140 AMS 11,970 ± 40 13,726–13,983 13,808 Seeds
Hozelec
UG-11623 25–28 AMS 130 ± 25 10–273 125 Seeds
UG-11624 51–53 AMS 150 ± 25 0–284 173 Bryophytes
GrN-30201 60–63 Conv. 3260 ± 45 3385–3580 3490 Bulk
GrN-30202 118–121 Conv. 7140 ± 60 7838–8154 7965 Bulk
GrN-30203 185–188 Conv. 10,190 ± 80 11,405–12,226 11,873 Bulk
GrN-30204 192 Conv. 10,540 ± 120 12,094–12,706 12,458 Bulk
UG-11627 194–196 AMS 11,780 ± 40 13,480–13,730 13,610 Seeds
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Hájková et al. 5
Figure 2. Diagram of particular peat components (in percentages), selected taxa of bryophytes, vascular plants, molluscs (in absolute values) and pollen taxa (in percentages) for Hozelec profile (HOZ).
Furthermore, some ecological groups of taxa are shown (for included taxa, see Appendices S3, S5, available online). The total pollen sum (TS = AP (arboreal plants) + NAP (non-arboreal plants) = 100%) was calculated
based on the terrestrial pollen sum; (semi)aquatic plants, Pteridophyta, algae, fungi, and the other non-pollen palynomorphs (NPP) were excluded. The percentages of (semi)aquatic taxa, spores and NPP were related
to the extended sum (AP + NAP + (semi)aquatic + spores + NPP = 100%).
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6 The Holocene
Figure 3. Diagram of particular peat components (in percentages), selected taxa of bryophytes, vascular plants, molluscs (in absolute values) and pollen taxa (in percentages; for details, see the legend of Figure 2)
for Valalská voda profile (VAL). Furthermore, some ecological groups of taxa are shown (for included taxa, see Appendices S3, S5, available online).
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Hájková et al. 7
Figure 4. Diagram of particular peat components (in percentages), selected taxa of bryophytes, vascular plants, molluscs (in absolute values) and pollen (in percentages; for details, see the legend of Figure 2) for
Brezové profile (BRE-box). Furthermore, some ecological groups of taxa are shown (for included taxa, see Appendices S3, S5, available online).
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8 The Holocene
Figure 5. Diagram of particular peat components (in percentages), selected taxa of bryophytes, vascular plants and molluscs (in absolute values) for Brezové profile (BRE-A1). Furthermore, some ecological groups
of taxa are shown (for included taxa, see Appendices S3, S5, available online).
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Hájková et al. 9
sp., Chenopodiaceae, Botrychium sp., Selaginella selaginoides,
cf. Gypsophilla repens (pollen type of the same name), and Ephe-
dra sp. (Ephedra fragilis type), with scattered shrubs of Juniperus
communis and Betula nana/humilis (few pollen grains of Betula
nana type). Pollen of other, perhaps heliophilous species such as
Ranunculus sp. (R. acris type), Silene sp. (S. vulgaris type) and
Potentilla sp. were recorded at the Hozelec site that provided the
best preserved pollen record.
The rise in temperature in the early Holocene was at first
reflected by a decline of P. sylvestris/mugo and steppe and tundra
elements, along with the increase of Picea abies and Betula
pendula/pubescens. Later, some deciduous temperate tree species
(e.g. Corylus avellana, Quercus spp., Tilia spp. and Ulmus spp.)
started to spread, but the pattern was locally different. The late
Holocene period was, in the study region, characterised by the
expansion of Abies alba, whereas Fagus was only sporadic com-
pared with the records from other Central European mountains.
Larix continually occurred from the late Glacial to present times.
Development of fen communities from the late
Glacial to middle Holocene
The late Glacial and early Holocene calcareous fens were charac-
terised by calcium carbonate precipitation and by light-demand-
ing fen plant and mollusc communities (for molluscs, see
Appendix S3, available online and for plant macrofossil, Appen-
dix S4, available online). In the bryophyte layer, we recorded
light-demanding species such as Scorpidium cossonii (BRE-A1,
HOZ), Tomentypnum nitens (BRE-A1), Palustriella commutata
(syn. Cratoneuron commutatum, VAL, HOZ), Campylium stella-
tum and Ditrichum crispatissimum (syn. D. gracile, HOZ). Mol-
lusc communities were composed of common open-country
species such as Vallonia pulchella (BRE-A1, HOZ), and species
of humid or marshy habitats Succinea putris (BRE-A1), Nesovit-
rea hammonis (HOZ) and Euconulus praticola (BRE-A1), but
also contained several characteristic glacial species such as Colu-
mella columella (BRE-A1, HOZ), Vertigo genesii (all sites), V.
modesta and V. parcedentata (BRE-A1). The bottom layers of all
three sequences contained Pupilla alpicola, a calcareous-fen spe-
cialist that has survived to the recent time in HOZ, but is extinct
in VAL as well as in BRE. The presence of small calcareous pools
was indicated by oogonia of Chara vulgaris (HOZ) and Potamo-
geton seeds and pollen (HOZ). Fen vegetation was represented by
sedges Carex flava agg. (HOZ, VAL), C. nigra (VAL), C. rostrata
(HOZ) and Trichophorum pumilum (BRE-A1). The presence of
Salix shrubs at fen sites was documented by both wood remains in
the fen deposits (BRE-box, VAL and HOZ) and also by pollen (all
localities). Also, trees or shrubs of Taxus baccata might occur in
the studied calcareous fens during the late Glacial and early Holo-
cene, as evidenced by wood remains found in the Valalská voda
deposit (see Hájková et al., 2012b for other fossil records of Taxus
in fens). Pollen assemblages further suggested the existence of
wet meadows and tall-herb vegetation at the fen margins, as evi-
denced by pollen of Scorzonera cf. humilis (pollen type of the
same name), Filipendula sp., Polygonum cf. bistorta (pollen type
of the same name) and Thalictrum sp.
During the middle Holocene, all glacial land-snail species
except P. alpicola disappeared definitely from all three study
fens. Nevertheless, the successional development differed among
these fens. At the Hozelec site, the shallow water basin (or pos-
sibly a small pool) had developed. Although the plant macrofos-
sil record was very poor (Valeriana cf. simplicifolia, Cirsium sp.
and Equisetum sp.), the other proxies, i.e., aquatic molluscs (e.g.
Valvata cristata and Anisus leucostoma), algae (Botryococcus
sp.) and pollen (Oenanthe cf. aquatica and Potamogeton natans
type.) clearly indicated a high and stable water level. Besides
aquatic communities, semi-terrestrial wetland habitats, including
calcareous fens were developed, as indicated by pollen (Cypera-
ceae, Cirsium sp., Equisetum sp., Peucedanum cf. palustre, Men-
tha sp., Lysimachia cf. vulgaris, Valeriana cf. dioica, V. cf.
officinalis and Iris sibirica; Appendix S2, available online) and
molluscs (Euconulus praticola, Oxyloma elegans and Vertigo
angustior; Appendix S3, available online). Species-rich open-fen
mollusc communities were evidently present during the entire
middle Holocene and contained, among others, highly special-
ised fen snail Vertigo geyeri, which started to spread after the late
Glacial/Holocene transition and which replaced here V. genesii, a
species characteristic of the late Glacial. Based on pollen data,
the site was surrounded by a spruce–alder carr, and a high water
level had most likely been a crucial factor in keeping at least the
central part of the site open.
At the Brezové site, we analysed two profiles of different
age. The older profile (BRE-A1) captured the patch that was
overgrown by spruce–alder carr already in the early Holocene,
as indicated by a high amount of wood remains. Only small
pools with Chara vulgaris and their banks could remain at
least partially open in the middle Holocene. The younger pro-
file (BRE-box) captured a patch where peat initiation occurred
later, at the beginning of the middle Holocene (about 8200 cal.
yr BP). At that time, ancient fen vegetation was composed of
boreal bryophytes Calliergon giganteum, Meesia triquetra and
Scorpidium scorpioides (the two latter species are recently
extinct at the site).
The sediment of the basal 30 cm (BRE-box) contained calcium
carbonate, which allowed fossilisation of mollusc shells that were
missing in the rest of the profile, with the exception of sub-recent
layers (0–19 cm). Three relict species still occurred at the study
site (Columella columella, Pupilla alpicola and Vertigo genesii;
Figure 4) at the beginning of the middle Holocene (ca. 8200 cal.
yr BP). The presence of shallow pools was indicated by oogonia
of Chara vulgaris, algae Pediastrum boryanum and seeds of
Potamogeton filiformis. Among sedges, Carex flava s.lat., C.
paniculata and Blysmus compressus occurred (Appendix S4,
available online). This part of the fen was also overgrown by a
rather dense spruce–alder carr later in the middle Holocene (from
140 cm upwards; about 4400 cal. yr BP). This woodland phase
was characterised by forest spring vegetation with Carex remota
and Glyceria nemoralis. At the Valalská voda site, the middle
Holocene record was completely missing, which could be caused
either by strong mineralisation under the dense alder carr or by
repeated water erosion by a nearby brook.
Late Holocene development
The calcareous sedge–moss vegetation resembling the modern
vegetation was largely established as late as in the late Holocene,
about 500 cal. yr BP at the Valalská voda site, about 140 cal. yr BP
at the Brezové site (consistent result from both profiles), and
between 3500 and 150 cal. yr BP at the Hozelec site; exact dating
was impossible because of a high rate of mineralisation or pres-
ence of sediment hiatus in this zone. The modern calcareous fen
vegetation was partially composed of the same vascular plants
(e.g. Carex flava agg., C. paniculata, C. nigra, Linum catharti-
cum and Menyanthes trifoliata) and bryophyte species (Campy-
lium stellatum, Palustriella commutata and Scorpidium cossonii)
that occurred previously in the older periods (for details, see
Appendix S4, available online). On the other hand, an important
group of species characteristic of present-day communities was
found only in layers dated to the period after modern deforesta-
tion (Carex davalliana, C. dioica and Eriophorum latifolium).
Similar to the plant assemblages, the modern mollusc assem-
blages established rather recently (BRE-A1 and VAL) except for
the Hozelec fen, where a high number of recently occurring spe-
cies already occurred during the middle Holocene (about 8000 cal.
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10 The Holocene
yr BP) and may thus represent continually persisting relicts. Spe-
cies composition during the middle Holocene was very similar to
that found recently and differed only by the presence of aquatic
species. On the contrary, most of the recently occurring land-snail
species appeared not long ago at the Valalská voda fen, but this
result may be partially confounded by the low species richness of
fossil samples. An intermediate situation could be reconstructed
at the Brezové site.
Ecology of relict snail species
Using 66 extant Altaian populations of four characteristic Full
Glacial snail species of temperate Europe, we reconstructed
mean annual, January and July temperatures for the studied fens
at the Pleistocene/Holocene transition (Table 3). Although there
were differences among the optima of particular species, the
main variation was found between preferences of Pupilla alpic-
ola (a species that survived in fens of the study area to recent
times) and three other species that became extinct approxi-
mately at the transition between early and middle Holocene.
Southern Siberian populations of these three latter species
expressed very consistent temperature preferences, with the
mean annual temperature varying between –3.07 and –1.15°C.
P. alpicola preferred climatically milder sites, with the optimum
temperature of 1.95°C.
Also, habitat features of the analysed sites in the Altai refu-
gium can provide further important data for reconstructions of
conditions at the study fens. While half of these Siberian sites
represented typically treeless fens and fen meadows (17 sites), the
other half consisted of fen shrubs (10 sites) and sparse fen wood-
lands (7 sites). These shrubby and woodland fens were even more
frequent habitat types when looking only at sites with the pres-
ence of more than two of these relict species. According to the
fossil samples from the analysed profiles, the glacial snails were
living in all three of these contrasting microhabitats – in shrubby
fens (HOZ and VAL), a treeless calcareous fen (BRE-box) and
also fen woodlands (BRE-A1 and VAL). Simultaneous presence
of fossils of light-demanding fen plants suggested the existence of
open patches in shrubby and woodland vegetation.
Discussion
In this study, we provide evidence that the application of the relict
concept to explain recent distributional, metacommunity and
diversity patterns of temperate fens is meaningful. We have
clearly documented that the whole-Holocene local continuity of a
calcareous fen is possible, and that populations of specialised fen
species can persist locally for millennia.
Long-term continuity of the habitat
Low-productive calcareous fens are dynamic ecosystems whose
character is determined by multiple factors including water chem-
istry, macroclimate (affecting the hydrological regime), autogenic
succession and disturbances, and nutrient enrichment by wild ani-
mals or man. Stratigraphical hiatuses and reversal developments
may frequently occur in fen sediments (Ammann et al., 2013;
Hájková et al., 2012a). Such high dynamics are probably the rea-
son for poor palaeoecological evidence of continual in situ persis-
tence of calcareous fens and their specialised plants.
Grootjans et al. (2006) reviewed the knowledge on the long-
term stability of calcareous fens and similar habitats. The longest
stability they reviewed concerned percolation mires in Germany
spanning about 3000 years (3000–6000 BP; Michaelis, 2002).
Our results from the Hozelec site provide evidence of much lon-
ger in situ stability of open-fen patches, from the late Glacial to
present times. We thus confirmed the hypothesis that a great
recent concentration of relict fen species is a result of a long,
continual Holocene history of calcareous fen vegetation (Hájek
et al., 2011). However, this hypothesis could not be verified
based on a single proxy, because of some hiatuses in the fossil
record, and only the combination of all three independent proxies
(pollen, macrofossils and snails) provided unequivocal evidence.
Pollen documented unspecified treeless wet habitats during the
late Glacial, while macrofossils documented calcareous fen veg-
etation around the late Glacial/early Holocene transition and in
the late Holocene, and specialised snail species indicated the
continuous existence of calcareous fen habitats since the early/
middle Holocene transition.
The mollusc succession at the Hozelec site showed the lowest
level of compositional turnover and species richness changes
throughout the whole profile (Appendix S3, available online).
Fossil snail records, in which more complete assemblages com-
pared with plants are usually preserved, hence appear to be cru-
cial for completing the evidence of long-term fen stability. The
reason for exceptional conservatism of some fens in the Western
Carpathians, such as the Hozelec fen, probably lies in the specific
hydrological systems with deep circulation of extremely mineral-
rich groundwater (Hájková et al., 2012a; Madaras et al., 2012)
that alleviate macroclimatic fluctuations and may block or even
reverse autogenic succession (Hájková et al., 2012a, 2013).
Sequences from the two other fens did not yield such an
unequivocal evidence of long-term local presence of calcareous
fen habitat or particular species. During the Holocene, these fens
showed extensive changes in species composition and richness of
snails, as well as plants. We expected the long-term persistence of
open-fen patches at the Brezové fen, where a high number of rel-
ict fen species occur at present (Hájek et al., 2011). In all cores
taken from this fen, however, the forested phase was virtually
without any light-demanding species (see Figures 4 and 5, Appen-
dix S4, available online). The most critical bottleneck for survival
of light-demanding species started after about 4400 cal. yr BP.
The only sign of possible persistence of small open-fen patches
was the presence of oogonia of Chara vulgaris that indicated the
presence of small calcareous pools, with the open-fen species
probably surviving on their shores. Our results confirm those of
Madaras et al. (2012), who drilled a series of cores throughout the
Brezové fen (not analysed by palaeoecological methods) and
reported on the existence of a layer of compact, very decomposed
dark peat with wood remains that completely overlay basal car-
bonate-rich peat. They concluded that the site was forested in the
Table 3. Variation of mean annual, mean January and mean July
temperature values for southern Siberian sites with the presence of
those glacial relict snail species, which we recorded in bottom layers
of the studied fen sequences.
Median Mean SD Min./Max.
Mean annual temp. (°C)
Pupilla alpicola −1.10 −1.01 1.92 −4.1/1.6
Vertigo genesii −1.80 −1.82 1.81 −5.2/−0.5
Columella columella −2.30 −2.26 1.36 −4.1/−0.2
Vertigo parcedentata −3.05 −2.89 0.79 −4.1/−1.6
Mean January temp. (°C)
Pupilla alpicola −17.60 −17.62 1.54 −20.0/−15.8
Vertigo genesii −18.80 −18.46 1.36 −20.8/−17.6
Columella columella −18.85 −18.88 0.81 −20.0/−17.6
Vertigo parcedentata −19.10 −19.20 0.50 −20.0/−18.4
Mean July temp. (°C)
Pupilla alpicola 14.80 15.38 2.72 11.3/19.5
Vertigo genesii 14.40 14.28 2.45 9.9/15.7
Columella columella 13.45 13.62 1.78 11.3/16.3
Vertigo parcedentata 12.55 12.81 0.99 11.3/14.4
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Hájková et al. 11
past. It is impossible to determine from our data whether the fen
species that were found in the bottom layers and then after the late
Holocene deforestation have persisted locally in small popula-
tions in a few open patches, or whether they re-colonised the site
by long-distance dispersal.
The third site, Valalská voda, was probably forested densely
for a long time, as indicated by both the long stratigraphical hiatus
and the poor representation of relict and specialised fen species in
the modern assemblages. The few relict species that occur today
at this site had to re-colonise or colonise the fen de novo after the
Wallachian colonisation. For example, shells of Vertigo geyeri,
the recently occurring relict snail, were found only in the young-
est layers of this profile.
Persistence and extinction of fen species
One of the aims of this study was to test the hypothesis about
whole-Holocene local survival of the species whose recent distri-
butional patterns suggest their relictualism from late Glacial times
with direct fossil evidence. So far, the evaluation of species relic-
tualism has been mostly based on indirect evidence such as phylo-
geography of modern populations (Ehrich et al., 2008; Lambracht
et al., 2007), specific recent distribution (Dítě et al., 2013), wider
distribution of a species in the past (Jankovská and Rybníček,
1988; Magyari et al., 1999), and correlations between the fen age
and fen specialists (Hájek et al., 2011). In contrast, continual
occurrences in peat profiles have been poorly documented.
We were successful in verifying whole-Holocene persistence
of an open calcareous fen (at the Hozelec site, Figure 2), but we
failed to confirm such continuity at the level of individual species.
A high water level at the Hozelec site during the middle Holocene
probably enabled the existence of treeless patches, but unfortu-
nately caused a hiatus in the macrofossil record. The longest local
continuity we found thus concerns the late Glacial relict snail spe-
cies Vertigo geyeri, which undoubtedly occurred continually over
more than 8000 years at this site. However, this species was not
recorded in the late Glacial samples in any profile studied, which
can be explained by its intolerance to extremely harsh climates.
Recently, it was found to avoid sites at high altitudes and latitudes
where it is replaced by Vertigo genesii. These two late Glacial
sibling Vertigo species rarely co-occur at one site even in the Alps
and Scandinavia where they are frequent today (Schenková et al.,
in press). A comparatively long in situ persistence was further
found for other open-country yet less tightly fen-associated snail
species such as Vallonia pulchella, Vertigo angustior and Nesovit-
rea hammonis (Appendix S3, available online).
We found a set of calcareous plant species that occurred in both
the old and the young deposits (e.g. Carex flava agg., C. nigra,
Bryum pseudotriquetrum, Campylium stellatum, Juncus articula-
tus and Scorpidium cossonii; see Appendix S4, available online),
but they are rather common today in the Western Carpathians and
are therefore not generally considered to be relicts from the cold
past. In addition, they did not show a statistically significant affin-
ity to ancient fens in the study of Hájek et al. (2011). Nevertheless,
the ancient fens could act as a source of these species after the
Wallachian colonisation. Most of the species with clear relict dis-
tributional pattern (see Hájek et al., 2011) were not found in our
profiles. It is difficult to determine whether their absence from fen
deposits was caused by taphonomic reasons (e.g. transient seed
bank and seed predation in the case of Primula farinosa) or
whether they truly did not occur in the late Glacial because of dif-
ferent environmental conditions. The environmental changes from
the late Glacial to recent times evidently caused certain species
exchange, as evidenced by the late Glacial and early Holocene
occurrence of fen species that are recently absent in the study fens
such as Trichophorum pumilum (BRE-A1), Potamogeton filifor-
mis (HOZ, BRE-box), or boreal bryophyte species Meesia
triquetra and Scorpidium scorpioides (BRE-box). These species
are very rare today in Central Europe and they are traditionally
considered to be relicts from the cold phases (Dítě and Šoltés,
2010; Rybníček, 1966).
Trichophorum pumilum is common in continental Asia, show-
ing a more compact European distribution range during the Full
Glacial as well as late Glacial and surviving recently in travertine
fens in the Western Carpathians (Dítě et al., 2013). Meesia trique-
tra and Scorpidium scorpioides are moss species that are recently
very rare and endangered across Central Europe (Kučera et al.,
2012), but they are common in various mire habitats in boreal and
arctic Eurasia (Hedenäs, 2003). During the late Glacial and early
Holocene, they had a broader distribution in Central Europe
(Dobrowolski et al., 2012; Hájková et al., 2012c; Jankovská,
1970; Magyari et al., 1999; Rybníček and Rybníčková, 1968).
Potamogeton filiformis is regularly present in cold-stage sedi-
ments (e.g. Gałka et al., 2014; Stachowicz-Rybka et al., 2009;
Wohlfarth et al., 2006) and today, it occurs widely in Northern
Europe and in the Alps (e.g. Lauber and Wagner, 2012; Rørslett,
1991).
Based on these findings, we can state that the late-Glacial
assemblages are at least partially analogous to the present-day
assemblages known from boreal and continental landscapes, at
least in terms of the presence of these boreal and continental ele-
ments, which are extremely rare in the Western Carpathians today.
However, it is unfortunately impossible to reconstruct the com-
plete species assemblages using macrofossils, because of tapho-
nomic constraints. We therefore cannot exclude that these boreal
and continental species co-existed with temperate fen species
such as Carex davalliana, C. dioica or Primula farinosa, the latter
being found in pollen in two late Glacial/early Holocene deposits
at lower altitudes in the Western Carpathians (Hájková et al.,
2013; Jamrichová, unpublished).
Possible causes of snail extinctions in temperate
Europe
The land-snail species characteristic of the European Full Glacial
period, which we surprisingly discovered in basal samples of all
studied profiles, enabled us to trace the history of their popula-
tions and Holocene extinction events in the Western Carpathians.
Generally, these species became extinct across the whole of tem-
perate Europe around the Pleistocene/Holocene transition (Horsák
et al., 2010; Ložek, 1964, 2001), but some of them retreated to
high mountain refugia in the Alps and Carpathians (Kerney et al.,
1983; Schenková and Horsák, 2013). For Columella columella, a
shift in habitat preferences was documented at the end of the Gla-
cial, when this originally xerophilous and characteristic loess-
dwelling snail species (Ložek, 1964) established large populations
in calcareous wetlands (Ložek, 2007 and our results). In recent
times, it commonly inhabits fens in cold regions of Norway
(Pokryszko, 1993) and the Alps (Kerney et al., 1983). Our records
suggest that during the late-Glacial climate oscillations, calcare-
ous fens could act as refugia also for other characteristic species
of loess snail fauna such as Vertigo parcedentata. Some of these
species have managed to survive in calcareous fens up to recent
times (e.g. Pupilla alpicola), but most of them became extinct
during the early Holocene (Ložek, 1964 and our results) across
the entire temperate Europe, except for some high mountain
regions. The reasons for these extinctions remain unclear and
only poorly resolved. At least three possible causes can be sug-
gested: (1) the pure ecophysiological effect of climate change, (2)
habitat change and (3) biotic interactions. As the level of interspe-
cific competition among land snails is believed to be low or neg-
ligible (e.g. Hylander et al., 2005; Waldén, 1981), which seems to
be true particularly for minute fen species (e.g. Horsák, 2006;
Horsák et al., 2014), we did not consider competition as the
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12 The Holocene
leading force of these extinctions. To disentangle the pure effects
of climate and habitat change is more challenging because the
postglacial habitat changes are driven mainly by the changing
macroclimate (e.g. Williams and Shuman, 2013).
Our fossil evidence suggests rather dynamic habitat conditions
at the study fens during the Holocene with respect to the water
regime and tree canopy. The question is whether these snail spe-
cies, adapted to a glacial landscape, could cope with these
changes. Analogous assemblages of these snails from their conti-
nental refugium in the Altai Mountains in southern Siberia
(Horsák et al., 2010; Meng, 2009) may bring a possible answer to
this question. In the Altai Mountains, these species dwell in alka-
line open-woodland fens (Horsák et al., 2010), most likely
because scattered trees and shrubs provide suitable shelter against
the harsh climate during the coldest months. Structurally, these
sites clearly resemble those we reconstructed based on our records
from the studied fen sequences. If these species can survive in
forested fens, the pure effect of climate changes might be more
important than subsequent changes in habitat structure towards
woodland stages.
The crucial role of climate change in extinction of glacial
snails in temperate Europe is further supported by the fact that
only Pupilla alpicola survived largely in the Western Carpathian
fens to recent times. Modern climatic demands of refugial popula-
tions of glacial snail species in the Altai Mountains indeed showed
that P. alpicola displayed the highest heat tolerance and even cer-
tain preference for a warmer macroclimate (Table 3). Only this
snail thus managed to survive all habitat and temperature fluctua-
tions throughout the Holocene in the Western Carpathian fens. In
contrast, Vertigo parcedentata, which became extinct throughout
Europe except for a single small area in Norway (Pokryszko,
1993), showed preference for the coldest areas. The other two
species, Vertigo genesii and Columella columella, were interme-
diate and indeed, they became extinct in the lowlands but sur-
vived in the high altitudes of the Alps and Carpathians.
Conclusion
In this study, we provide evidence that the application of the relict
concept to explain recent distributional, metacommunity and
diversity patterns of temperate fens is meaningful. Based on the
data from the Hozelec fen in the Western Carpathians, we have
clearly documented that the local continuity of a calcareous fen is
possible for the whole Holocene, and that populations of special-
ised fen species persisted locally for millennia (maximum about
8000 years in this study). Moreover, because the habitat main-
tained stable abiotic conditions (calcium richness, light and high
water table) for 12,000 years, we can suppose the possibility of
even longer in situ survival of the relict fen species, but direct
evidence for such a long time span is still missing. Nevertheless,
fen habitats fed by abundant, mineral-rich groundwater from deep
circulation appear to be good postglacial refugia, comparable to
other stable habitats such as rocks, screes or alpine tundra. This
finding is rather surprising, because fen habitats are known to be
rather prone to natural successional changes. Indeed, for the other
two fens for which we could anticipate similar continuity, consid-
erable dynamics, including forested phases were found, and there
was no clear evidence of long-term local survival.
Despite unequivocal evidence of whole-Holocene persis-
tence of a calcareous fen habitat at least at one site, we generally
found rather low similarity between modern and the oldest fen
assemblages. The species typical of European glacial periods
disappeared from the studied Carpathian fens during the middle
Holocene, with the last record of recently extinct glacial snail
species at about 8200 cal. yr BP (the Brezové fen), most proba-
bly because of climate change. Boreal bryophytes Meesia tri-
quetra and Scorpidium scorpioides, which are recently rare in
the Carpathians, disappeared from the same fen around 4400 cal.
yr BP after canopy closing. The modern composition of both
plant and mollusc fen communities seems to be largely a prod-
uct of the late Holocene assembly in most of the Western Car-
pathian fens. The intense deforestation during the late Middle
Ages (e.g. the Wallachian colonisation) has led to the develop-
ment of calcareous fen assemblages that are rather similar across
the Western Carpathians. In some old fens, however, the relicts
from the late Glacial stages, persisting over the middle Holo-
cene habitat bottleneck, enriched newly assembled communities
and made these old fens inestimable and irreplaceable in terms
of habitat and species conservation. The Hozelec and partially
also the Brezové fen belong among these unique sites, which
underlines the need to make their protection and conservation
management a priority.
Acknowledgements
We are grateful to Ondřej Hájek for preparing the map, Stanislav
Němejc and Jan Myšák for help with the profile sampling, and
Zuzana Formánková for laboratory work.
Funding
Our palaeoecological research was supported by projects of the
Czech Science Foundation P504/11/0429, institutional support of
Masaryk University, and long-term research development project
no. RVO 67985939. Research in the Altai Mountains was sup-
ported by the project P504/11/0454.
Supplementary Material
Additional information may be found in the online version of this
article.
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... In line with our hypotheses, we explain this difference in relation to the different Holocene histories of the two fen habitat types. Since the level of environmental stress is lower at rich fens, making them also prone to successional shifts (Hájek et al. 2020a), they seem to be more sensitive to shrub and tree encroachment, as evidenced by frequent occurrence of wooded phases during the Middle Holocene (Moravec and Rybníčková 1964;Rybníček and Rybníčková 1987;Hájková et al. 2018) as compared to calcareous fens (Hájková et al. 2013(Hájková et al. , 2015. As a result, the entire-Holocene in situ persistence of species might be rarer Table 4 Species of vascular plants, bryophytes and land snails that occur with higher frequency in older rich fens than would be expected by chance (null model with 10,000 randomizations) ...
... Some concepts, such as the Dark Diversity concept or concept of neorefugia (Nekola 1999), anticipate potential future occurrence of species if local habitat conditions are suitable. Our results, along with the previous observations from calcareous fens (Hájek et al. 2011a;Horsák et al. 2012;Hájková et al. 2015), however, draw attention to the importance of site age. This variable may significantly affect species composition and richness of a site, or even of other sites forming a regional metacommunity. ...
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Increasing evidence for the effects of Holocene history on modern biotic communities suggests that current explanations of community patterns and conservation strategies require revisiting. Here we focused on Central European rich fens that are at high risk among mire habitats because of their relatively low environmental stability, and hence sensitivity to successional shifts. At each of 57 study sites, inventory of specialist species of bryophytes, vascular plants and land snails, measurements of local environmental conditions, area, and radiocarbon dating were conducted. We used Moran’s I spatial autocorrelation, multiple linear regression models, MDS, db-RDA, and null models to identify drivers of species richness and occurrence. We tested the importance of site age and historical metacommunity dynamics expressed by regional age of the habitat for the diversity of three taxonomic groups of fen organisms differing in dispersal and life history strategies. The richness of specialist species was affected by local environmental conditions and area in all three groups, but the effect of regional age was significant and positive for vascular plants and snails, once the effect of fen area was set as a covariable. We identified 11 species significantly associated with ancient fens independently of site area and pH effects; this group includes species currently considered to be umbrella species in European habitat conservation (the moss Hamatocaulis vernicosus and the snail Vertigo geyeri). The effect of fen age per se on the communities of specialists calls for the incorporation of age into conservation schemes. Restoration or de novo construction of peat-forming fens cannot compensate for a loss of ancient fens.
... davalliana) was a priority criterion (Coldea 1997, Felbaba-Klushyna 2010. We have identified that these relict vegetation types of the most calcareous fens have their distribution centre in the Inner Western Carpathians where the relict fens have been indeed frequently reported (Hájková et al. , 2015; in other countries, they have been recorded only rarely (Romania: Morariu et al. 1985). Outside the Western Carpathians, they are abundant in the Alps (e.g. ...
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Calcareous and rich fens harbour the unique biodiversity of plants and invertebrates. They areextremely sensitive to landscape changes because oftheir island nature. In the Carpathians, theyare still well-preserved, but their number has substantially decreased. Knowledge about theirvariability and classification into vegetation units, a baseline for efficient nature conservancy, isstill insufficient in the Eastern Carpathians, where phytosociology has used different methodolo-gies than in the Western Carpathians. It has resulted in artificial boundaries in the distribution ofvegetation types and low compatibility with modernEuropean habitat classification schemes.Here we gathered a large set of vegetation-plot records, sampled by the unified sampling protocol.The aim was to uncover the principal variation in compositional data, identify resulting clusterswith the hitherto reported vegetation units, and create the unified classification system adjustedfor the entire Carpathian territory. In line with previous ecological studies, the unsupervised clas-sifications (Twinspan, beta-flexible clusteringmethod) largely mirrored the base saturation gra-dient and distinguished between relict fens and younger fen grasslands. We defined formally thecores of 10 vegetation units well reproduced by unsupervised classifications and used them asprototypes in semi-supervised k-means clustering. The final 10 clusters essentially correspondwith phytosociological associations, with five of them being reported for the first time for Roma-nia. These vegetation units were well-separated in the principal coordinate analysis, whose firstaxis separated relict fens from younger fen grasslands, while the second axis followed the waterlevel gradient largely. Groundwater pH and conductivity contributed to forming significantcompositional gradients. Climate (temperature, precipitation, number of hot days above 30 °C)and specific edaphic conditions contributed to thediversification of the vegetation types. Ouranalyses supported the classification of fen grasslands into both the tufa-forming and the peat-forming ones, belonging to different associations and Habitat Directive units, both occurring inall countries including Romania, rather than havinga single separate Eastern-Carpathian associa-tion. We provide strong evidence for distinguishing theSphagno warnstorfii-Tomentypnetaliaorder and its alliancesSphagno warnstorfii-Tomentypnion nitentis,Stygio-Caricion limosaeandSaxifrago hirculi-Tomentypnionin Romania, the latter missing in other Carpathian countries. Thefinal unified classification system will make Carpathian vegetation types of rich and calcareousfens applicable to continental habitat classification schemes.
... However, recently growing evidence that much of the area remained unglaciated during the Last Glacial Maximum (LGM), corroborated by results of palaeoecological and molecular phylogeographic studies, has largely altered such view (for an overview see 30,31 ). Now it is generally accepted, that the Carpathians acted as refugium not only for temperate biota during the LGM but, during warmer episodes, also for the cold-adapted taxa, either at higher elevations (e.g., 32,33 ) or in habitats such as fens and peat bogs at lower elevations 34 . Most of the phylogeographic studies in the Carpathians focused on the terrestrial biota; however, the region has also been presumed as an important refugium for aquatic taxa. ...
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The Carpathians are one of the key biodiversity hotspots in Europe. The mountain chain uplifted during Alpine orogenesis and is characterised by a complex geological history. Its current biodiversity was highly influenced by Pleistocene glaciations. The goal of the current study was to examine the phylogenetic and demographic history of Gammarus balcanicus species complex in the Carpathians using multiple markers as well as to delimit, using an integrative approach, and describe new species hidden so far under the name G. balcanicus . Results shown that divergence of the studied lineages reaches back to the Miocene, which supports the hypothesis of their survival in multiple micro refugia. Moreover, the increase of their diversification rate in the Pleistocene suggests that glaciation was the driving force of their speciation. The climatic changes during and after the Pleistocene also played a major role in the demography of the local Carpathian lineages. Comparison of diversity patterns and phylogenetic relationships of both, the mitochondrial and nuclear markers, provide evidence of putative hybridisation and retention of ancient polymorphism (i.e., incomplete lineage sorting). The morphological examination supported the existence of two morphological types; one we describe as G. stasiuki sp. nov. and another we redescribe as G. tatrensis (S. Karaman, 1931).
... This pattern may explain the refugial occurrence of several late-glacial relicts at the study sites and spring mires in general. Current palaeoecological evidence for bryophytes, vascular plants and land snails of the study area (Dítě et al., 2017;Hájková et al., 2015;Horsák et al., 2015) directly supports the relictual status of many species from these T A B L E 2 Descriptive statistic of all used environmental parameters F I G U R E 3 3 Variation in differences between air mesoclimate temperature and water temperature measured at three plot types. Cold/warm extreme buffering represents a difference between January/July air temperature and 5th/95th percentile of the lowest/ highest water temperature values, respectively taxonomical groups (e.g. ...
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... However, recently growing evidence that much of the area remained unglaciated during the Last Glacial Maximum (LGM), corroborated by results of palaeoecological and molecular phylogeographic studies, has largely altered such view (for an overview see Bálint et al. 2011;Mráz & Ronikier 2016). Now it is generally accepted, that the Carpathians acted as refugium not only for temperate biota during the LGM but, during warmer episodes, also for the cold-adapted taxa, either at higher elevations (e.g., Schmitt & Varga 2012;Ronikier 2011) or in habitats such as fens and peat bogs at lower elevations (Hájková et al. 2015). Most of the phylogeographic studies in the Carpathians focused on the terrestrial biota; however, the region has also been presumed as an important refugium for aquatic taxa. ...
Preprint
Full-text available
The Carpathians are one of the key biodiversity hotspots in Europe. The mountain chain uplifted during Alpine orogenesis and is characterised by a complex geological history. Its current biodiversity was highly influenced by Pleistocene glaciations. The goal of the current study was to examine the phylogenetic and demographic history of Gammarus balcanicus species complex in the Carpathians using multiple markers as well as to delimit, using an integrative approach, and describe new species hidden so far under the name G. balcanicus . Results shown that divergence of the studied lineages reaches back to the Miocene, which supports the hypothesis of their survival in multiple micro refugia. Moreover, the increase of their diversification rate in the Pleistocene suggests that glaciation was the driving force of their speciation. The climatic changes during and after the Pleistocene also played a major role in the demography of the local Carpathian lineages. Comparison of diversity patterns and phylogenetic relationships of both, the mitochondrial and nuclear markers, provide evidence of putative hybridisation and retention of ancient polymorphism (i.e., incomplete lineage sorting). The morphological examination supported the existence of two morphological types; one we describe as G. stasiuki sp. nov. and another we redescribe as G. tatrensis (S. Karaman, 1931).
... These mosses are typical of the calcareous fen habitats (cf. Hajek et al., 2006) and were commonly documented from the Holocene deposits of the spring-fed fen ecosystems at lowlands (Pietruczuk et al., 2018;Dobrowolski et al., 2019) and in the mountains (Hájková et al., 2013(Hájková et al., , 2015Gałka et al., 2018). The timing of the above-discussed changes in the environmental conditions at the Raganu Mire is concurrent with the increased water level recorded at Apšuciems Mire at ca. 1200 cal. ...
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The calcareous substrate of spring-fed fens makes them unique islands of biodiversity, hosting endangered, vulnerable, and protected vascular plants. Hence, spring-fed fens ecosystems require special conservation attention because many of them are destroyed (e.g. drained, forested) and it is extremely difficult or even impossible to restore the unique hydrogeological and geochemical conditions enabling their function. The long-term perspective of paleoecological studies allows indication of former wetland ecosystem states and provides understanding of their development over millennia. To examine the late Holocene dynamics of a calcareous spring-fed fen (Raganu Mire) ecosystem on the Baltic Sea coast (Latvia) in relation to environmental changes, substrate and human activity, we have undertaken high-resolution analyses of plant macrofossils, pollen, mollusc, stable carbon (δ 13 C) and oxygen (δ 18 O) isotopes combined with radiocarbon dating (AMS) in three coring locations. Our study revealed that peat deposits began accumulating ca. 7000 cal. yr BP and calcareous deposits (tufa) from 1450 cal. yr BP, coinciding with regional hydrological changes. Several fire events occurred between 4000 and 1600 cal. yr BP, which appeared to have had a limited effect on local vegetation. The most significant changes in the forest and peatland ecosystems were at 3200 cal. yr BP associated with a dry climate stage and high fire activity, and then between 1400 and 500 cal. yr BP potentially associated with temperature changes during the Medieval Climate Anomaly (MCA) and Little Ice Age. Hydrological disturbances in the peatland catchment from 1400 cal. yr BP were most likely strengthened by human activity (deforestation) in this region. The relationship between the development of this peatland and changes in its catchment area, such as land cover changes or fluctuations in groundwater levels, suggest that protection and restoration of spring-fed fen ecosystems should also include the surrounding catchment. The presence of calcareous sediments, as well as appropriate temperature and local hydrological conditions appear to be the most crucial factors controlling Cladium marisus populations in our site-currently at the eastern limit of its distribution in Europe.
... Information on fossil bryophytes may help us reconstruct the history of localities, including past vegetation, environmental conditions and their changes, because many of them are highly adapted to specific environmental conditions such as high or low water pH, mineral richness, water level or nutrient content (Dickson 1973, Birks 1982. Furthermore, several fen bryophytes are traditionally considered glacial or postglacial relicts (Rybníček 1966, Hájková et al. 2015 in temperate Europe. These groups include species that are supposed to have been much more common in the glacial period and later retreated into refugia. ...
Article
Full-text available
Palaeoecological analyses of old peat deposits can bring information on the past distribution of bryophyte species. In this paper, we report historical occurrence of fen mosses that are currently rare and declining in Central Europe. This paper brings new data about the presence of fen mosses in old peat deposits in (i) the forest-steppe zone of Ukraine (Drepanocladus trifarius, Meesia triquetra, Scorpidium scorpioides), (ii) the Bohemian-Moravian Highlands in the Czech Republic (Helodium blandowii, Paludella squarrosa, S. scorpioides), and (iii) the Malé Karpaty Mts in Slovakia (S. scorpioides). The records suggest common occurrence of the mosses in the study regions during the Late Glacial and Early Holocene.
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Continentality is a globally significant gradient influencing broad-scale biogeographical patterns. An excellent example is the transition from the European temperate forest biome to the continental steppe and forest-steppe of Eurasia. One of the biogeographic crossroads where the two biomes meet is the Western Podillia in the western part of Ukraine. It is known for its rich biodiversity with a mixture of steppe, forest and montane species, despite a relatively humid climate suitable for closed-canopy forests. Biologists have postulated the refugial character of the local steppes, but a modern paleoecological reconstruction of the environmental history of the region has been lacking. We fill this gap here with a multi-proxy study (pollen, plant and mollusc macrofossils, microcharcoal, geochemistry) of two profiles sampled in calcareous fens adjacent to species-rich steppe grasslands. To link the reconstructed environmental history with the history of human settlement, we compiled available archaeological records from the studied region. Together, the analyzed profiles cover the entire Holocene and the end of the Last Glacial period, as shown by high-quality age-depth models. All studied proxies support the hypothesis that an open or semi-open landscape existed in Western Podillia during the Holocene. The complete absence of wood remains in Holocene sediments, and the persistence of fen specialists showed the exceptional long-term stability of open wetlands. The continuous presence of pollen of light-demanding plants, low abundance of closed-canopy trees compared to open-canopy trees, and stable concentrations of geochemical indicators of erosion suggest a semi-open landscape with a mosaic of forests, steppe grasslands, and other open habitats. Multivariate analysis revealed the similarity of pollen assemblages with sites in the forest-steppe zone at the interface between the Pannonian Basin and the Western Carpathians. The continuous presence of non-woody microcharcoal in high abundance suggests a role of fire in maintaining open habitats, and the archaeological record provides evidence of human activity throughout the Holocene near the study sites. Comparison with modern pollen spectra suggests that the landscape was probably somewhat more forested in the past than today, but rather by open-canopy trees. Our results indicate that Western Podillia has become a biogeographic crossroads not only because of its location on the border between Central and Eastern Europe, but also because of the unusual combination of relatively humid climate and continuity of open or semi-open landscapes since the Last Glacial.
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