SPIDER (ARANEAE) COMMUNITIES OF SCREE SLOPES IN THE CZECH REPUBLIC

2005·10.5 MB·English

by  Vlastimil Ruzicka

2005. The Journal of Arachnology 33:280-289
SPIDER (ARANEAE) COMMUNITIES OF SCREE SLOPES IN
THE CZECH REPUBLIC
Vlastimil RMicka: Institute of Entomology, Czech Academy of Sciences,
Branisovska 31, CZ-370 05 Ceske Budejovice, Czech Republic
Leos Klimes: Institute of Botany, Czech Academy of Sciences, Dukelska 135, CZ-
379 01 Tfeboh, Czech Republic
ABSTRACT. We assessed the effects ofenvironmental factors on spidercommunities in screes (sloping
mass of coarse rock fragments) of the Czech Republic, based on catches from 325 pitfall traps, exposed
for 177-670 days, from 1984-2000. Bootstrapresampling was appliedtotestforfuzzinessofthepartitions
in cluster analysis of the samples. Two distinct spider communities were identified. The first one was
confinedto sites where ice is formedandpersists until late summeroroverthewholeyear. Thiscommunity
consists of numerous relict spiders, such as Bathyphantes simillimus buchari Ruzicka 1988, Diplocentria
bidentata (Emerton 1882) andLepthyphantes tripartitus Miller & Svaton 1978, possibly persisting inthese
cold screes from the early postglacial period. The other community included all other sites, irrespective
of their environmental characteristics. Monte Carlo simulations were used to test the significance of en-
vironmental factors and their interactions on the studied communities. Ice formation near the traps and
position of the traps within individual screes were the most significant factors, followed by the depth of
the traps within the scree, diameter of stones forming the scree, and altitude. A marginally significant
effect was found for organic content in the scree matter, whereas presence oftrees and phytogeographical
districts appeared non-significant. Our analyses support the view that spiders inhabiting cold screes in
Central Europe belong to a unique relict community of species requiring cold and stable microclimate.
Keywords; Scree slopes, environmental factors, ice formation, CCA, Monte Carlo simulations
At middle elevations scree slopes (or talus, showed that some of the screes host peculiar
an accumulation of coarse rock debris that and surprisingly species-rich fauna of inver-
rests against the base ofan inland cliff; Allaby tebrates. Recent ecological studies demon-
& Allaby 2003) represent eommon terrain strated that the screes represent island-like
forms in larger parts of Europe. Most stone ecosystems, supporting species which do not
&
aecumulations result from frost weathering of occur in the surrounding areas (Moseler
primarily compact rocks. These serees are Molenda 1999; Kubat 2000). Repeated field
widespread especially in the subarctic and in observations supported by microclimatical
mountains in mid-latitudes, where a perigla- measurements have shown that some screes
cial climate (i.e., climate of areas adjacent to function as large coolers, accumulating cold
a glacier or ice sheet) prevailing in the recent air that persists in some parts of the screes
geological past promoted their development. over the whole season. The thermic regime of
Screes situated at middle elevations have at- the screes is often extremely conservative,
tracted the attention of ecologists only recent- largely independent of temperature fluctua-
ly, perhaps due to logistic constraints (difficult tions above-ground, both within and between
access, a permanent danger of falling stones, years. At the bottom of some screes ice is
landslides, etc.). Relatively small cavities sit- formed, sometimes persisting there over the
uated deeply in the scree are usually covered whole year, even if temperatures above-
by unstable layers of stones, making non-de- ground are higher by 30 °C or even more
structive studies rather difficult or almost im- (Gude et al. 2003). Therefore, the stability of
possible. Further, the low densities ofmost in- the temperature regime with extremely cold
vertebrates colonizing the inner parts ofscrees temperatures throughout the year and perma-
make short-term studies inefficient. In spite of nently high humidity enables persistence of a
these difficulties, current ecological research unique community of invertebrates, including
280
RUZICKA AND KLIMES-SPIDERS OF SCREE SLOPES 281
several representatives of arctic fauna which Czech Republic belong to the Proterozoic and
retreated from otherhabitats in CentralEurope Palaeozoic Bohemian Massif, only the east-
more than 10,000 years ago. ernmost part is pervaded by the Tertiary
The research focused on the fauna of in- mountain system of the western Carpathians.
vertebrates in screes of the Czech Republic The Bohemian Massif was long ago trans-
was considerably intensified after modified formed by erosion into a levelled terrain,
pitfall traps were developed (Ruzicka 1982, which was, during the Alpine formation of
1988b). These traps were exposed by the se- mountains, disrupted by faults, fractures in
nior author for several months up to two years rock strata; elevated crustal blocks formed
in most important scree localities in the coun- mountain regions (particularly border moun-
try over the course of the last two decades. tains), and the volcanic region of Ceske Stfe-
Numerous surprising findings have been re- dohon Mts. in the north ofthe Czech Republic
ported, based on this research, including was formed. The system of deeply cut river
twelve species ofspiders, mites and diplopods valleys was formed during the Tertiary and,
new to the Czech Republic (Ruzicka 1988b, especially, during the Quaternary (Lozek
1994, 2000, 2002; Ruzicka et al. 1989; Ruz- 1988). Due to its geology and geomorpholo-
icka & Aetus 1998; Ruzicka & Hajer 1996; gy, the territory of the Czech Republic is rich
Zacharda 1993) and five species/subspecies in various boulder accumulations (Ruzicka
new to science (Ruzicka 1988a; Zacharda 1993).
2000a, b, c). The results ofthe studies carried Material was collected from 66 localities
out on nearly 66 localities revealed also acon- distributed all over the Czech Republic (Fig.
siderable heterogeneity of spider communities 1). Elevations of the localities ranged from
m
inhabiting the screes. While some localities 270-1550 a.s.L The investigated screes are
host numerous relict species (see Discussion), formed by andesite, basalt, conglomerate,
other sites are relatively poor in biogeograph- limestone, phonolite, quartzite, sandstone,
ically and ecologically interesting spiders. granite and other kinds ofrock. The height of
Also, a considerable variation was observed scree fields from the foot to the top varied
within individual localities, with great differ- between 10 and 250 m, slope angles ranged
ences between individual parts of the screes. between 20° a—nd 40°.
These observations resulted in several ecolog- Sampling. The animals were usually
ical questions that we address in this paper: trapped in modified pitfall traps made ofrigid
1) What are the environmental factors respon- plastic (Ruzicka 1982, 1988b). The traps con-
sible for the observed variation in species sisted of a board (20 x 25 cm), which forms
composition of spider assemblages in the an artificial horizontal surface (note that a flat
screes? 2) Is the occurrence of relict species horizontal soil surface is not present in scree
in screes correlated with some environmental slopes) and a can inserted in the centre of the
factors? 3) Is there a sharp boundary between board. Traditional pitfall traps (simple cans)
spider communities of cold and warm sites were also used. The cans contained a mixture
within individual screes? of 7% formaldehyde and 10% glycerol with a
To answer these questions we compiled all few drops of a surfactant. The traps were
available records of spiders from screes ofthe placed among the stones. Field research was
Czech Republic, obtained by pitfall traps ex- conducted from 1984-2000. In total, 325 traps
posed for a longer time, and added available were installed, most of them (85%) for more
information on environmental factors, either than 300 days.
measured or estimated in other ways at sites The catch, especially from deeper scree lay-
where the spiders were collected. This result- ers, is often poor in species. To obtain more
ed in a relatively large and complete dataset representative samples, we combined catches
which we used in the analysis. from traps placed at the same position along
METHODS the scree slope in individual localities. This
— resulted in 128 samples. —
Study area and localities. The Czech Environmental characteristics. In total,
Republic is situated in the temperate zone of eight environmental characteristics were reg-
Europe between 48° 33' and 51° 03' N, and istered: elevation (m a.s.L); scree type (1 =
12° 05' and 18° 51' E. Major parts of the bare scree slopes, 2 = scree slopes partly
282 THE JOURNAL OF ARACHNOLOGY
—
Figure 1. Location of the studied screes on a grid map of the Czech Republic. The circles represent
one or several localities used in the analysis.
overgrown by solitary trees, 3 = scree forests, Canonical Correspondence Analysis (DCA)
corresponding to a gradient from bare to forest was used to estimate species turnover along
screes); position ofpitfall traps along the tem- the main direction of variability. After that
perature gradient in scree field (1 = lower CCA (Canonical Correspondence Analysis)
margin, 2 = middle part, and 3 = upper mar- implemented into the CANOCO program (ter
gin of the scree); ice formation near the trap Braak & Smilauer 1998) was performed to
(1 = no ice formation, 2 = temporal ice inside test the effects of individual variables and
scree, melting in summer, 3 = permanent ice their interactions on species composition.
forming permafrost-like conditions); typical Monte Carlo simulations with 10,000 permu-
size of stones in the scree (diameter ranging tations were calculated to assess the signifi-
from 0.1-10 m); depth below the surface in cance of individual environmental factors and
which the trap was installed (ranged from 0- their interactions. In these analyses the factors
5.0 m); substrate around the trap (1 = bare which were not used as explanatory variables
stones, 2 = soil, 3 = detritus, 4 = mosses, were defined as covariables, to remove their
ranges from sterile to organic substrate); phy- effects on the results and to obtain a net effect
togeographical district (1 = thermo-, 2 = of individual environmental variables. Using
meso-, 3 = oreophyticum, characterized by this approach we could perform tests that are
ANOVA
vegetation on a broader scale, Slavik 1984). counterparts to but for multivariate
In addition, three covariables were used: data.
type of trap (1 = a pot, which was a low ef- Spider communities were classified by a
hciency trap; 2 = a pot sunken into a board, cluster analysis based on Ward’s method, us-
which was considered a high efficiency trap); ing Euclidean distances for quantitative data
number oftraps at a site (ranging from 1-11); (Jongman et al. 1995, p. 178), calculated for
number of days during which the trap was ex- log-transformed catches, using the Syn-tax
posed. — program by Podani (2001). The sharpness of
Data analysis. In the numerical analyses the resulting classification was tested using a
we always used the whole data set, i.e., all bootstrap resampling, in which stability of
localities and all species. The input data were partition at a given level was tested by resam-
log-transformed prior to analysis. Detrended pling the original data, according to Pillar
RUZICKA AND KLIMES-SPIDERS OF SCREE SLOPES 283
(1999). The outcome of this testing indicates 1. Species occurring exclusively in bare
whether groups in the partition reappear more scree slopes (and in adjacent underground
often in resampling data than expected on a spaces) and in scree forests: Acantholycosa
random basis. norvegica (Thorell 1872), Bathyphantes sim-
Nomenclature follows the catalogue of spi- iliimus buchari Ruzicka 1988, Clubiona al-
ders of the Czech Republic (Buchar & Ruz- picola Kulczyhski 1882, Comaroma simoni
icka 2002). Species characteristics were also Bertkau 1889, Diplocentria bidentata (Emer-
taken from this source. Voucher specimens are ton 1882), Kratochviliella bicapitata Miller
deposited in the collection of V. Ruzicka. 1938, Lepthyphantes notabilis Kulczyhski
1887, Lepthyphantes improbulus Simon 1929,
RESULTS
— Lepthyphantes zimmermanni Bertkau 1890,
Site characteristics. The strongest signif- L1i8o71c)ranum rutilans (Thorell 1875), Meta men-
icant correlation between pairs ofthe eighten- ardi (Latreille 1804), Micrargus apertus (O.
vironmental characteristics was found be- R-Cambridge 1871), Neon levis (Simon
tween elevation and phytogeographical Pholcomma gibbum (Westring 1851),
district (r “ 0.70). This reflects the crucialrole Porrh,omma myops Simon 1884, Porrhomma
of elevation in the distribution of plant com- rosenhaueri (L. Koch 1872), Rugathodes bel-
munities at a broader scale. The position of licosus (Simon 1873), Saaristoafirma (O. R-
the traps was strongly negatively correlated Cambridge 1905), Trogloneta granulum Simon
with the incidence of ice at the traps (r = 1922, Wubanoides uralensis (Rakhorukov
-0.49), implying that traps situated at the 1981).
lower margin of the screes were often sur- 2. Species of scree slopes, occurring also in
rounded by permanent ice whereas traps other habitats (in brackets): Lepthyphantes le-
placed at the upper margin were free of ice. p1r8o7s2u)s (Ohlert 1865), Liocranum rupicola
As expected, bare scree slopes were usually (Walckenaer 1830), Nesticus cellulanus
built oflarge boulders whereas forested screes (Clerck 1757), Pholcus opilionoides (Schrank
developed on gravel screes (r = 0.40). Further, 1781), Sitticus pubescens (Fabricius 1775)
scree sites with large amounts oforganic mat- (synanthropic), Ceratinella major Kulczyhski
ter and covered by mosses usually developed 1894, Megalepthyphantes collinus (L. Koch
in warm regions (r = —0.32), at lower ele- Tegenaria silvestris L. Koch 1872 (for-
= , &
vations (r —0.34) and at the lower margin ests), Lepthyphantes tripartitus Miller Sva-
of the screes (r = —0.35). ton 1978, Theonoe minutissima (O. R.-Cam-
Ice formation was negatively correlated bridge 1879) (peat bogs), Agraecina striata
with elevation (r ~ —0.20). Even ifelevations (Kulczyhski 1882) (lowland forests), Wal-
of the sites (270-1550 m) spanned the range ckenaeria capita (Westring 1861) (rock
of elevations in the Czech Republic almost steppes), Cryphoeca silvicola (C.L. Koch
completely, surprisingly the screes with ice 1834) (spruce forests), Porrhomma egeria Si-
formation were found atratherlow elevations; mon 1884 (caves and subalpine belt).
the screes with permanent ice filling were sit- The cluster analysis of samples revealed
m
uated at 350-650 a.s.l., the screes with tem- two distinct groups, indicating that two clearly
m
poral ice filling at 270-700 a.s.l. The ice separated spider communities can be identi-
was found more often in sterile screes without fied in the screes (Fig. 2). The bootstrap re-
organic matter and deeper in the scree than in sampling showed a partitioning at this level.
screes with organic matter and near traps sit- For lower levels, i.e. when considering parti-
uated closely to the scree surface (r — 0.26 tioning to a higher number ofclusters, we ob-
—
and r —0.21, respectively). All these cor- tained non-significant results. Accordingly, all
relations were significant—at P < 0.05. clusters except for those labelled in Fig. 2 A
Species composition. In total, 1047 spi- and B should be interpreted as fuzzy, not dis-
ders were captured, belonging to 176 species tinctly separated from each other. All ten sam-
of 22 families. Based on our knowledge on ples from sites at which permanent ice was
ecological demands ofall spider species in the observed and most samples from sites at
Czech Republic (Buchar & Ruzicka 2002), the which temporal ice formation was registered
following sets of species can be identified were included in cluster A. The other cluster,
among the captured spiders: B, included all other localities.
284 THE JOURNAL OF ARACHNOLOGY
14
12
10
Zi
4
2
ICE
DB
BSB
LT
—
Figure 2. Spider communities in Czech screes, as revealed by a cluster analysis of samples. The A
and B clusters were supported by bootstrap resampling. ICE = ice formation (2 = temporal ice inside
scree, melting in summer; 3 = permanent ice forming permafrost). Presence of three indicators of ice
incidence (DB = Diplocentha bidentata, BSB — Bathyphantes simillimus buchari, LT = Lepthyphantes
tripartitus) is indicated by stars.
The longest gradient in DCA was 6.4, in- most important for the pattern of similarity
dicating that the response model suitable for among samples.
the analysis is unimodal. Therefore, we used The CCA analysis used to test the effect of
CCA for direct and CA for indirect gradient individual variables showed that ice formation
analysis. First four axes ofthe CCA explained and position of the traps on the scree slopes
%
8.9 of total variance and a test of all ca- had the strongest effects on species composi-
nonical axes was strongly significant (P = tion and abundance of spiders. The effect of
0.001). The CCA ordination of samples (Fig. the two factors was strongly significant, as
3) clearly separated localities belonging to the documented by the ordination diagram. The
two clusters oflocalities. The overlap between depth at which the traps were placed also
envelopes encompassing localities belonging showed a strong effect on species composi-
to the two clusters was relatively large, how- tion, similarly to elevation and stone diameter.
ever, localities belonging to cluster A showed The last factor showing a significant effect
clearly higher scores of the first ordination was the substrate, however, its effect was only
axis in comparison with localities belonging marginally significant. Several interactions
to cluster B. While direct gradient analyses, also played a significant role (Table 1). Even
such as CCA, are searching for the pattern iftheir effect was usually less strong than that
caused by environmental variables, its coun- of the above mentioned variables, they were
terpart, correspondence analysis (CA), reflects still significant, suggesting that species com-
similarity in species composition and abun- position and abundance of spiders in screes is
dance of individual samples. The CA ordina- affected by numerous factors, often interact-
tion (not shown) revealed a pattern very sim- ing with each other in a complicated way.
ilar to that of CCA, and the amount of Therefore, it is not surprising that spider com-
variation explained by the first ordination axis munities of screes are not sharply delimited
was similar (3.7 and 2.7 %, respectively). This and, except for the two largest groups, they
indicates that the environmental factors used show a fuzzy pattern with little distinct—ness.
in the analysis belong to those that are the Spiders and environmental factors* The
RUZICKA AND KLIMES-SPIDERS OF SCREE SLOPES 285
—
Figure 3. CCA ordination of samples. Arrows indicate the effect of environmental variables. Full
circles = samples belonging to A cluster in Fig. 2, crosses = samples belonging to B cluster. ELE:
elevation; ICE: ice formation near the trap; DEPTH: depth below the surface, in which the trap was
installed; POS: position of pitfall trap along the temperature gradient in scree field; DIAM: typical size
of stones; SUBSTR: substrate around the trap; PHYTO: phytogeographical district; SCREETYP: from
bare scree to scree forest.
relatively high number of samples scattered illimus, and Walckenaeria capita. Several spe-
over the whole Czech Republic enabled a cies were caught mainly at lower elevations:
more detailed analysis of the effect of envi- Lepthyphantes improbulus (up to 400 m
ronmental factors on individual species. a.s.L), Pholcus opilionoides (up to 750 m),
Analyses of the relationship between envi- Liocranum rupicola (up to 800 m) and Phol-
ronmental variables and the number of cap- comma gibbum.
tured spiders of individual species (linear re- Metellina merianae occurred primarily in
gression) showed that species found mainly at scree forests; Acantholycosa norvegica, Lep-
higher elevations included Clubiona alpicola thyphantes notabilis, Clubiona alpicola were
m
(only above 700 a.s.L), Wubanoides ura- recorded exclusively on bare, open scree
lensis (only above 930 m), Bathyphantes sim- slopes.
286 THE JOURNAL OF ARACHNOLOGY
—
Table 1. Results of the CCA analyses applied to log abundances of spiders caught in pitfall traps, r:
species-environment correlation on the first axis, var: percentage of species variability explained by the
first ordination axis. F: the F-ratio statistics for the test on the trace. P: corresponding probability value
obtained by the Monte Carlo permutation test. The variables notusedas explanatoryvariables inindividual
analyses, were used as covariables. Type of the trap, number of traps at a site and number of days for
which the trap was exposed were used as covariables in all analyses. ELF: elevation; ICE: ice formation
near the trap; DEPTH: depth below the surface, in which the trap was installed; POSITION: position of
pitfall trap along the temperature gradient in scree field; DIAM: typical size ofstones; SUBSTR: substrate
around the trap; PHYTO; phytogeographical district; SCREETYP: from bare scree to scree forest.
Explanatory variables r var F P
ELE 0.812 1.5 1.67 0.0017
ICE 0.828 1.7 1.84 0.0001
DEPTH 0.833 1.4 1.54 0.0003
POSITION 0.803 1.7 1.87 0.0001
DIAM 0.809 1.4 1.59 0.0089
SUBSTR 0.8 1.2 1.3 0.0497
PHYTO 0.732 0.9 1.03 0.3920
SCREETYP 0.767 0.9 0.95 0.5951
ELE X DIAM 0.778 1.3 1.47 0.0215
DIAM X ICE 0.843 1.4 1.54 0.0185
SUBSTR X ICE 0.847 1.3 1.42 0.0192
ELE X DEPTH 0.809 1.3 1.38 0.0323
SUBSTR X DEPTH 0.81 1.2 1.3 0.0396
PHYTO X SUBSTR 0.774 1.1 1.23 0.1060
SCREETYPE X SUBSTR 0.783 1 1.07 0.3015
Lepthyphantes notahilis and Pholcus opi- bidentata and 1 specimen of L. tripartitus
lionoides colonized mainly upper scree mar- were collected by moss sieving.
gins; Lepthyphantes tripartitus and Diplocen- Orb weavers Metellina merianae and Meta
tria bidentata occurred mainly at lower menardi preferred spaces among largerstones;
margins. in contrast, Lepthyphantes notabilis, Pholcom-
The dependence on ice formation is sharp ma gibbum, Acantholycosa norvegica were
in some spiders: Rugathodes bellicosus, Lep- more abundant at sites with smaller stones.
thyphtantes notabilis, Tegenaria silvestris, The species occurring mainly at the scree
Nesticus cellulanus, Pholcomma gibbum, surface included Acantholycosa norvegica,
Meta menardi, Acantholycosa norvegica, Lio- Diplocentria bidentata, whereas Porrhomma
cranum rupicola, Pholcus opilionoides avoid- myops, Rugathodes bellicosus, Meta menardi,
ed sites with ice formation, whereas Lepthy- Nesticus cellulanus, Wubanoides uralensis
phantes tripartitus, Diplocentria bidentata were found mainly in the depth of the screes.
and Bathyphantes simillimus buchari at lower Finally, species found mainly at the surface
elevations were confined to these sites. of bare stones included Lepthyphantes nota-
Diplocentria bidentata and Lepthyphantes bilis, Clubiona alpicola, Rugathodes bellico-
tripartitus occurred together at sites where ice sus, Meta menardi, Theonoe minutissima, and
is formed. Along the gradient of substrate Wubanoides uralensis.
type, L. tripartitus preferred more detritus-rich
DISCUSSION
sites, whereas D. bidentata colonised more
mossy habitats. Diplocentria bidentata tended Balch (1900) was possibly the first who
to occur at the surface, whereas L. tripartitus documented ice formation in scree slopes at
occurred in deeper layers. These trends were middle (but not at higher) elevations. We
Linivocally supported by the separate sieving showed that ice is regularly formed in screes
of moss and detritus on Klic Mt. on 12th Oc- also from 270-700 m. According to Gude et
tober 1999: 28 specimens ofL. tripartitus and al. (2003) lower parts of scree slopes are in-
6 specimens ofD. bidentata were collected by tensively cooled during short periods of win-
detritus sieving, whereas 66 specimens of D. ter frost. Cold air penetrates inside the screes
RUZICKA AND KLIMES-SPIDERS OF SCREE SLOPES 287
only during periods with no (or limited) snow floristically similar communities also occur at
cover. Long-term data from three south Bo- higher elevations of mountains further south
hemian meteorological stations support this (Tallis 1991). Current disjunct distribution of
hypothesis. They indicate a negative relation- some spider species is a result of their with-
ship between the number offrost days without drawal from Central Europe caused by chang-
snow cover and altitude: there are 23 frost ing climatic conditions in the Pleistocene.
days without snow per year in Ceske Bude- Twenty-seven spider species of the Czech
jovice at 389 m, 19 such days at Kasperske arachnofauna exhibit boreo-montane type of
Hory (737 m) and only 10 frost days without geographical distribution (Ruzicka in prep.).
m
snow per year on Churahov at 1,118 a.s.L They occur in higher latitudes and have dis-
Mountain scree slopes do not markedly cool junct, island-like populations in Central Eu-
in winter, because frost air cannot penetrate rope. The present findings indicate that some
the scree slopes through the snow cover. scree spiders in Central Europe could be re-
Spatial heterogeneity of invertebrates in garded as relicts of former climatic periods
scree slopes was studied by Molenda 1989; (‘‘glacial relicts”). Four ofthese species occur
&
Ruzicka et al. 1995; V. Ruzicka 1990, 1996, exclusively in scree slopes (Buchar Ruzicka
2002; J. Ruzicka 1996. The position of a site 2002).
along the scree slope was designated as the Having a distribution center in Siberia/
main factor influencing species distribution by North Asia, Wubanoides uralensis and Acan-
Brabec (1973) in his pioneer study. We found tholycosa norvegica occur only in several lo-
that the effects of position of the trap on the calities in Central Europe (Schikora 2004;
scree slope and ice formation are strongly sig- Marusik et al. 2003), independent of ice for-
nificant. Ice formation is aprincipal factorand mation. Bathyphantes similUmus shows about
ice is usually formed on the lower margin of the same general distributional pattern. In con-
scree slopes. However, concave slope forms trast, Diplocentria bidentata has a Holarctic
can be formed by various slope denudation distribution. In Scotland, northern England
processes also in the middle part of a scree and Wales it occurs locally with a low abun-
slope (Demek et al. 1975; Ruzicka 1999c). In dance in highlands (Harvey et al. 2002). In
such cases, ice can be formed also in the mid- Central Europe it is known only from the peat
dle part of a scree slope. bogs in Harz, Germany, situated at the highest
Elevation patterns in spiders and mites of elevations (Wiehle 1965); in the Czech Re-
screes also have been documented by Ruzicka public on hilltops in the Krkonose Mountains
& Zacharda (1994) who focused on scree hab- (2 specimens) and on lower margin of frozen
itats in our highest mountains in the Krkonose scree slopes (243 specimens). The occurrence
National Park, and by V. Ruzicka (1996), who of the latter two species is closely tied to ice
studied spiders in screes at low elevations of formation in scree slopes. The same is true for
the Podyji National Park. the Central European mountain species Lep-
Spatial distribution of spiders in screes was thyphantes tripartitus. The occurrence of the
studied by Ruzicka 1999a, 2002 and Ruzicka three species at lowerelevations is closely tied
et al. 1995. Temperature is a key factor re- to the present periglacial temperature regime
sponsible for the presence or absence of spe- in frozen scree slopes, and the presence of
cies in individual parts along the slope. The these species indicates the palaeorefugial
dependence of L. tripartitus on detritus ex- character of these habitats (Zacharda et al. in
plains the fact, that this species colonizes the press), i.e. island-like habitats inhabited by
whole profile of the lower margin of the populations offormerly more widespread spe-
screes, from the surface to the depth of about cies (Nekola 1999).
one meter, whereas D. bidentata, which is re- Deep layers of screes represent shallow
stricted to moss cushions, cannot colonize subterranean spaces, in which gradual adap-
deeper layers. tation to the stable environment of deep sub-
Land surfaces at higher latitudes in the terranean spaces takes place (Ruzicka 1999b).
northern hemisphere support a range offorest, Species, which preferentially colonise deep
scrub, tundra and peatland communities at the scree layers, exhibit leg elongation, depigmen-
present day that may collectively be called the tation, body diminishing, and eye reduction
“coldland complex”. Physiognomically and (Ruzicka 1988a, 1990, 1998; Schikora 2004).
288 THE JOURNAL OF ARACHNOLOGY
We found some of these species on several Czech Socialist Republic]. (S, Hejny & B. Sla-
localities (R. bellicosus, B. s. buchari); on the vik, eds.). Academia, Praha, (in Czech, English
other hand, the occurrence of Porrhomma summary).
monyeoplsocaalnidtyCoonmlay.roTmhae sriemaosnoin ifsorknthoewirnrfarriotmy MarAussiukr,vYe.yMo.f,EGa.sNt.PAazlaaerakricntaic&LyS.coKsoipdoanee(nA.ra2n0e0i3)..
II. Genus Acantholycosa E Dahl, 1908 and re-
(a special combination of environmental fac- lated new genera. Arthropoda Selecta 12(2):101-
tors vs. our inability to penetrate more deep
148.
in scree?) remains unknown. Molenda, R. 1—989. Kafer in kaltlufterzeugenden
ACKNOWLEDGMENTS Blockhladen dkologische Untersuchungen an
einem stark bewetterten Spaltenokosystem. 4
This study was supported by the Grant Rundschreiben der Arbeitsgemeinschaft Rhein-
—
Agency of the Czech Republic project No. ischer Koleopterologen. Pp. 103-111.
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