Download (Araneae, Gnaphosidae) along the altitudinal gradient of

Journal of Biogeography (J. Biogeogr.) (2005) 32, 813–831
ORIGINAL
ARTICLE
The distribution of ground spiders
(Araneae, Gnaphosidae) along the
altitudinal gradient of Crete, Greece:
species richness, activity and altitudinal
range
M. Chatzaki1*, P. Lymberakis1, G. Markakis2 and M. Mylonas1,3
1
Natural History Museum of Crete, University
of Crete, Irakleio, 2Technological Education
Institute of Crete, Irakleio and 3Department of
Biology, University of Crete, Irakleio, Greece
ABSTRACT
Aim To study the altitudinal variation of ground spiders (Araneae, Gnaphosidae)
of Crete, Greece, as far as species composition, species richness, activity and range
of distribution are concerned.
Location Altitudinal zones (0–2400 m) along the three main mountain massifs
of the island of Crete.
Methods Thirty-three sampling sites were located from 0 to 2400 m a.s.l. on Crete,
and sampled using pitfall traps. Material from the high-activity period of Gnaphosidae (mid-spring to mid-autumn) was analysed. Sampling sites were divided into
five altitudinal zones of 500 m each. Statistical analysis involved univariate statistics
(anova) and multivariate statistics, such as multidimensional scaling (MDS) and
cluster analysis (UPGMA) using binomial data of species presence or absence.
Results Species richness declines with altitude and follows a hump-shaped
pattern. The activity pattern of the family, as a whole, is not correlated with
altitude and is highly species-specific. In the highest zone, both species richness
and activity decline dramatically. The altitudinal range of species distribution
increases with altitude. On the Cretan summits live highly tolerant lowland
species and isolated residents of the high mountains of Crete. Two different
patterns of community structure are recorded.
*Correspondence: M. Chatzaki, Natural
History Museum of Crete, University of
Crete, PO Box 2208, 71409 Irakleio, Crete,
Greece.
E-mail: [email protected]
Main conclusions Communities of Gnaphosidae on Crete present two distinct
structures following the altitudinal gradient, these being separated by a transitional
zone between 1600 and 2000 m. This study supports previous results which show a
hump-shaped decline in species richness of Gnaphosidae along altitudinal gradients,
leading to a peak at 400–700 m, where an optimum of environmental factors exists.
This makes this zone the meeting point of the often opportunistic lowland species
with the older and most permanent residents of the island. Rapoport’s rule on the
positive correlation of the altitudinal range of species distributions with altitude is
also supported. The high activity recorded for the species that persist on the high
mountains of Crete is indicative of a tolerant arachnofauna, and is considered to
result from relaxation of competitive interactions with other species. This is related
to a reduction in species numbers, shortening of the activity period on high
mountains and the unique presence of high mountain species that thrive only
there. As shown in our study, strategies to cope with altitude are species-specific.
Therefore, there cannot exist one single model to describe how animals react to
the change in altitude, even under the same environmental conditions.
Keywords
Activity, altitudinal gradient, altitudinal range, Crete, Gnaphosidae, ground
spiders, Mediterranean, mountain ecology, pitfall traps, species richness.
ª 2005 Blackwell Publishing Ltd www.blackwellpublishing.com/jbi
doi:10.1111/j.1365-2699.2004.01189.x
813
M. Chatzaki et al.
INTRODUCTION
The effect of altitude on biodiversity has been a topic of great
interest for many earlier and contemporary biogeographers.
During the nineteenth century latitudinal and elevational
gradients in diversity were considered direct responses to
climatic changes and energy interactions in the environment
(see historical review in Lomolino, 2001). These were later
interpreted as the species-energy theory by Wright (1983).
Recent researchers connected mountain ecology with the
species–area relationship of island biogeography (MacArthur,
1972), because of the similar conditions prevailing for both
types of ecosystems (small area, isolation, restricted spatial
heterogeneity). The negative effect of latitude on species
richness and latitudinal range, or Rapoport’s rule (Stevens,
1989) has also been correlated with the same phenomenon
along altitudinal gradients (Stevens, 1992; Brown et al., 1996).
The latter is explained as a result of the wider ecological
tolerances of organisms at higher elevations, a crucial characteristic which they have to possess in order to withstand the
wider climatic fluctuations to which they are exposed. Lawton
et al. (1987) ascribed the effect of elevation on species richness
to the following reasons: (1) reduction in productivity with
elevation; (2) reduction in the total area; (3) reduction in
resource diversity; and (4) harshness and unpredictability of
the conditions prevailing at higher elevations.
Two more phenomena have been related to the negative
effect of altitude on species richness, the ‘mid-domain effect’
(Colwell & Lees, 2000) or ‘ecotone effect’ (Lomolino, 2001),
i.e. the peak in species richness at mid elevations, due to the
increasing overlap of species ranges towards the centre of a
domain or minor peaks at transitions between elevational
communities, and the ‘rescue effect’ (Brown & Kodric-Brown,
1977), i.e. the reduced likelihood of a population at higher
elevations to be rescued by individuals dispersing from other
zones when compared with populations at lower elevations.
Stevens (1992) proposed the Rapoport-rescue hypothesis,
which is the extension of the previous idea to species level,
suggesting that species richness is inflated in lower latitudes/
altitudes by the emigration of high-altitude species at the
margins of their ranges due to wider tolerance, while taxa from
lower elevations cannot expand their upper limit of elevational
range. In total, this would mean that extinction rates of species
increase with elevation and so does isolation, in contrast to
immigration rates, which decrease with elevation (Stevens,
1992; Lomolino, 2001).
Although the negative effect of altitude on diversity is
broadly documented (Lawton et al., 1987; McCoy, 1990;
Stevens, 1992; Brown et al., 1996; Lomolino, 2001; Sanders,
2002), the pattern of diversity decline is still controversial.
One group of scientists favours a monotonic decrease in
species richness with increasing elevation (Claridge &
Singhrao, 1978; Lawton et al., 1987; Wolda, 1987; Fernandes
& Price, 1988; Sfenthourakis, 1992; Stevens, 1992 and
references therein) and another group favours a hump-shaped
pattern, where the peak of species richness occurs at an
814
intermediate elevation (Bosmans et al., 1986; McCoy, 1990;
Colwell & Hurtt, 1994; Rahbek, 1997; Fleishman et al., 1998;
Sánchez-Cordero, 2001; Grytnes & Vetaas, 2002; Sanders,
2002) (for a detailed review see also Lomolino, 2001 and
Sanders, 2002). In insects, both patterns have been observed
(Sanders, 2002 and references therein). According to McCoy
(1990), the latter pattern is more pronounced in predominantly, or totally, herbivorous insects, such as Coleoptera,
Homoptera and Hemiptera.
Apart from species richness, changes that occur in the
abundance of a species along altitudinal gradients are often
similar to changes along its geographical range (Whittaker,
1952; Hagvar, 1976; Claridge & Singhrao, 1978; Randall, 1982).
Abundance appears to be higher at the centre of a species range
and lower near the edges (Brown, 1984; Brussard, 1984; Brown
et al., 1996). The pattern of abundance of a species along
altitudinal gradients must be highly species-specific, as it is
related to many factors such as responses to climate changes, to
food quantity and quality, to natural pressure of enemies and
to interspecific competition (see Lawton et al., 1987 for
detailed citations).
Evidence for the value of Rapoport’s rule along elevation
gradients emerges from surveys of plants, mammals, reptiles
and insects (Stevens, 1992). More detailed surveys verify this
rule for butterflies (Fleishman et al., 1998), grasshoppers
(Claridge & Singhrao, 1978), ants (Sanders, 2002) and partially
isopods (Sfenthourakis, 1992). According to Brown et al.
(1996), Rapoport’s rule is closely related to general factors
which limit the range of distributions along geographical or
ecological gradients, i.e. increasing physical stress in one
direction, and increasing numbers and impacts of biological
enemies in the other. Therefore, it is a very dynamic, speciesspecific phenomenon, partly depending on global climatic
changes and on human activities.
Concerning spiders, not many detailed studies have been
carried out focusing on the relationship between species
richness and altitude or other of the above questions on a
species level. Maurer & Hänggi (1991) presented the altitudinal
variation of spider species in Switzerland, reporting a more or
less linear decline and an abrupt decrease in the number of
species above the timberline (only 7% of the total number of
species of the country occur above 2300 m). Although very few
species occupy the whole altitudinal range of the Swiss Alps
(21 species), about half of the total arachnofauna have wide
altitudinal range, their distribution extending from the valleys
to the timberline. Referring to the invertebrate diversity
(including spiders) at high altitudes of the Central Alps,
Meyer & Thaler (1995) reported a gradual decline of species
within the main life zones from 1800 to 3500 m and a stepwise
decline of species at the main borders. Bosmans et al. (1986)
studied the spider communities along an altitudinal gradient in
the French and Spanish Pyrénées (700–2475 m), concentrating
mainly on the community structure and the zoogeographical
patterns formed by the geographical distributions of the
spider species. Although not analysed, their results favour the
hump-shaped pattern of altitudinal distribution of the species
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Altitudinal distribution of ground spiders
(at the zone 1100–1500 m). An ecological survey of ground
spiders along altitudinal gradients in Norway (Otto &
Svensson, 1982) demonstrated the same pattern of species
decline from 0 to 800 m altitude, a positive correlation of the
number of eurychronous species and of the range of altitudinal
distribution, indicating the persistence of some widely distributed and easily dispersed species at high elevations. The
abundance of spiders declines along altitudinal gradients of
south Appalachian Mountains of North Carolina, Virginia and
Maryland (McCoy, 1990) with maximum abundance recorded
at low (but not the lowest) elevations.
This study examined the distributional patterns (species
richness, activity, altitudinal range and community structure) of the dominant family of ground spiders of Crete,
Gnaphosidae, along the altitudinal gradient (0–2400 m)
formed by three main mountain massifs, namely Lefka Ori,
Psiloreitis and Dikti. It would seem that these ecological
features are closely related to the history of the island and the
way of formation of its fauna. Therefore, associations
concerning the origin of the species occurring at different
altitudinal zones and the possible ways they reached these
zones are also given. Patterns of the above-mentioned
ecological factors are first analysed on a regional–altitudinal
base using altitude as a continuous parameter and then by
dividing sites into five altitudinal zones of 500 m each. Details
of special features of each mountain massif are analysed
separately.
MATERIALS AND METHODS
Study area
Geomorphology
Crete is the largest island of the south Aegean island arc and is
situated at its centre (3450¢–3540¢ N latitude, 2330¢–
2620¢ E longitude). It is the fifth largest island of the
Mediterranean after Sicily, Sardinia, Cyprus and Corsica, its
total surface covering 8.261 km2. Because of the intense
tectonic dynamics occurring in this area, Crete presents a
great geomorphological variation, being a ‘miniature continent’ (Rackham & Moody, 1996). Within such a small surface, a
great variety of habitats and climatic factors are present,
ranging from the insular character of the coasts to a fully
continental character as one goes inland and approaches the
high altitudes of its mountains.
The main characteristic of the island geomorphology is the
high percentage of mountainous regions, 39% of its surface
being above 400 m, 12.5% above 800 m and 1.6% above
1600 m. Three main mountain massifs are situated along
Crete: Lefka Ori in the western part, Psiloreitis in the central
part and Lasithiotika Ori (Dikti and Thrypti) in the eastern
part. Although the highest summit is found in Psiloreitis
(2.456 m), the largest mountainous range is found in Lefka
Ori: its highest summit is 2.453 m and there are another
56 summits over 2000 m.
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
When referring to the main characteristics of the island,
Bonnefont (1972) reports the decrease in altitude from west to
east, and the great fragmentation and asymmetry between
the north and south coast of Crete, the former being more
hospitable than the latter. The southern slopes of the main
mountain massifs of Crete are much steeper, with very steep
slopes close to the coasts forming lots of gorges.
Climate
Crete has a typical Mediterranean climate with 5–7 months of
arid, hot and dry summers, alternating with shorter periods of
rainy, mild winters. There are not sufficient meteorological
data, especially for the high mountains. However, there is a
remarkable gradient of temperature, precipitation, winds and
humidity across the main axes of the island, north to south,
west to east and from the coasts inland and upwards.
South, east and inland lowlands are warmer than the rest of
the regions, both in summer and in winter, except for inland
winters that are cooler than the coastal ones (Rackham &
Moody, 1996). Mean annual temperatures are 2 C lower in
the south than in the north of Crete (Pennas, 1977) and they
fall 6 C per 1000 m altitude (Grove et al., 1991). The range of
temperatures is much narrower near the coast than in the
mountains, due to the more maritime character of the former
(Strid, 1995).
Although there are no records for precipitation above
900 m, Rackham & Moody (1996) estimate that at the top of
Lefka Ori the annual precipitation must be as high as
2000 mm. In southern Lefka Ori, snow fall above 1400 m a.s.l.
can be several metres, but the resulting water disappears into
the porous crystalline limestone immediately after the snow
melts in May. This harsh landscape forms the ‘high desert’, a
term coined by Rackham & Moody (1996) to describe a unique
environment that does not exist in the other two mountain
massifs.
Geological history
The history of the south Aegean island arc dates back to the
middle Miocene (15–11 Ma), when intense fragmentation and
the first subductions of the Hellenic arc started to take place,
transforming the southern parts of ‘Aegaiida’ (the united land
mass comprising what is today the Hellenic peninsula and the
Aegean Sea) into separated island forms (Dermitzakis &
Papanikolaou, 1981; Le Pichon & Angelier, 1981). More recent
evaluations of the geodynamic evolution of the Aegean area
support the idea that such events that contributed to the
separation of Crete initiated at least 26 Ma (Meulenkamp
et al., 1988). Although there is not full agreement about the
periods and duration of land connections of Crete with
neighbouring continental areas, it is certain that Crete has been
fully isolated since 5 Ma.
Cretan mountains are quite new in geological time. Until
the early Pliocene (5 Ma) Crete was composed of a mosaic
of landmasses that did not exceed the altitude of 500 m
815
M. Chatzaki et al.
(Meulenkamp et al., 1988). The altitudinal zone above 1500 m
was formed as a result of pronounced uplifts that took place
after the Pleistocene (1.5 Ma) (Meulenkamp et al., 1994).
Vegetation
Phrygana is the most widespread formation on the island,
although irregularly distributed and showing a specific altitudinal zonation and ecological differentiations (Strid, 1995).
Phrygana are found from sea level to the highest summits, but
with the ratio of annual : perennial plant species decreasing
from low to high altitudes. Lowland and middle altitude
phrygana are composed of thorny aromatic shrubs such as:
Sarcopoterium spinosum, Coridothymus capitatus, Phlomis cretica, P. lanata, P. fruticosa, Cistus spp., Genista acanthoclada,
Calicotome villosa, Euphorbia spp., Balota spp. and others. At
higher altitudes other species (chamephytes) such as Berberis
cretica, Rhamnus saxatilis, Prunus prostrata, Satureja spinosa
and Astragalus angustifolius dominate. Beyond the timberline,
only scarce vegetation composed of small cushion-like shrubs
exists. In the present study, habitats of this type are separated
into phrygana near the coast (CP), inland phrygana (IP) and
sub-alpine shrubs (SS), following the altitudinal gradient
(Appendix 1).
Maquis (M) on Crete are often intermixed with phrygana, the
limits between the two being vague (Rackham & Moody, 1996).
This is mainly due to overgrazing of the region. Apart from the
above species, other typical maquis species are Ceratonia siliqua,
P. terebinthus, shrub-like Quercus coccifera, Pistacia lentiscus,
Arbutus unedo, Juniperus phoenicea, J. oxycedrus, Erica arborea
and others usually reaching 1–2 m height, or even more. These
formations may reach an altitude of c. 600 m.
The upper limits of forest growth reach altitudes from
1600 m (southern slopes) to 1800 m (northern slopes). Pinus
brutia (P) is the dominant species up to 1200 m. This is the
commonest forest formation of Crete, being found from sea
level to such altitudes. The rest of the woodland types on Crete
are very scarce: the Quercus coccifera forest on the southern
slopes of Psiloreitis (area of Rouvas, psi1000a) and the
Cupressus sempervirens–Quercus coccifera–Acer sempervirens
formations on the southern slopes of Lefka Ori (area of
Anopoli, lo1200) are among the most characteristic ones. Clear
altitudinal zonation, such as evergreen broadleaves–deciduous
forests–conifer trees, does not exist on Crete (Rackham &
Moody, 1996).
Methodology and statistical analysis
A total of 33 sampling sites were selected along the island of
Crete (Fig. 1) starting from sea level and reaching the highest
elevations of 2400 m. Sites include the most characteristic
habitat types of the island, i.e. phrygana, maquis, areas close to
wetlands, pine, kermes oak and cypress forests, and sub-alpine
shrublands (see Appendix 1). Following the relative representation of these habitat types on Crete, the majority of sites are
shrublands that are represented by different species associations, depending on the altitudinal zone. No urban areas were
sampled; therefore, habitat diversity of the lowlands is not fully
represented in this study.
In all sites material was collected by pitfall traps, using
ethylene glycol as a preservative. Pitfalls were set and changed
at 2-month intervals except for the sites at Lefka Ori, where
they were changed each month (see Appendix 1). Collection
of material covered the period of high activity of the family
Gnaphosidae, i.e. from mid-spring to mid-autumn. More
than two samples were collected at each site. Spiders of this
family were identified to species level and only mature
individuals were counted. Because pitfall traps register
Figure 1 Map of sampling sites on Crete.
816
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Altitudinal distribution of ground spiders
Table 1 Altitudinal zones on Crete: altitudinal limits, code
names, number of sites and number of species sampled to each
one of them
Altitudinal
zone (m)
Code
name
Number
of sites
Number
of species
0–499
500–999
1000–1499
1500–1999
2000–2400
ZER
LOW
MID
TOP
PEAK
14
6
6
4
3
44
39
28
19
5
activity patterns of arthropods and are only partly affected by
the population size of taxa (Maelfait & Baert, 1975),
quantitative data were not used for further statistical analysis.
The effect of seasonality on activity patterns is the subject of
another paper (M. Chatzaki et al., unpubl. data), therefore in
the present study it was reduced by using mean values of
samples at each site. It is for this reason that winter material
was not included in the analysis so that samples within the
high-activity period of the family could be considered as
equal sampling units as regards seasonality. In order to
balance sampling effort for all sites, the number of individuals per sample was transformed to the number of individuals per 100 trap days and the mean values of samples per
site were used for each species (Appendix 2). The same
transformation was used for the whole family, by summing
the above mean values of all species at each site.
Sites were divided into five altitudinal zones of 500 m each,
starting from sea level. Table 1 shows the number of sites
included in each of the above zones as well as the species
richness of each zone. Species collector curves were created with
EstimateS6b1a (version 6.5.6 for WindowsTM, 1985–2000).
Basic statistical tests were conducted with Statistica 6.0 (Statsoft
Inc., 1984–2001) and SPSS8 (SPSS Inc., 1989–1997, Standard
version). Two-way anova was first used to test for the
significance of differences in species richness and activity
among sites in relation to the mountain massif and the
altitudinal zone they belong. Multidimensional scaling (MDS)
(James & McCulloch, 1990) conducted with PRIMER5.2.2
(Primer-E Ltd, 2001) was used in order to visualize the
similarities among sites of the investigation based on the species
recorded on them. The ordination was based on the Bray–Curtis
distance on presence-absence data. Cluster analysis (UPGMA),
based on Jaccard’s coefficient of similarity (Krebs, 1998), was
performed in order to detect in more detail the stability of
patterns along the mountains of Crete and the ecological factors
that influence faunal similarities among sites.
RESULTS
Species composition
Table 2 shows the species recorded at each altitudinal zone. In
total, 54 species of ground spiders were recognized. Nine
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
species do not occur in the first altitudinal zone (Drassodes
oreinos, Gnaphosa bithynica, Haplodrassus minor, H. signifer,
Micaria dives, Poecilochroa senilis1, Scotophaeus scutulatus,
Synaphosus palearcticus and Drassyllus sp.). Nine species can
be characterized as exclusively lowland species, occurring
only up to 500 m (Berinda ensigera, Berlandina plumalis,
Leptodrassus hadjissaranti, L. manolisi, Micaria pygmaea,
Nomisia sp., Scotophaeus peninsularis, Trachyzelotes lyonneti,
Z. nilicola).
Above 2000 m there are five species in total. Drassodes
oreinos, a recently described species (Chatzaki et al., 2002b),
and G. bithynica, being present only at Lefka Ori and Psiloreitis
(Chatzaki et al., 2002a), are recorded on the Cretan mountains
above 1200 m and 1600 m respectively. The remaining species
– Z. creticus, Z. subterraneus and Z. labilis – occur at all
elevational zones of Crete, the first being Cretan endemic, the
second Palearctic and the third presenting unclear taxonomical
status (Chatzaki et al., 2003). Among these species, G. bithynica
and Z. creticus were not present at Dikti mountain.
Apart from the above-mentioned differences, some species
present deviations concerning the upper limit of their
distributions at the three main mountain massifs. For instance,
Pterotricha lentiginosa, Callilepis cretica, Zelotes caucasius and
Z. subterraneus reach 1950 m in Psiloreitis and 1750 m in
Dikti, but do not exceed 800 or 1600 m in Lefka Ori.
Species richness
Species collector curves were created using all sites together
(Fig. 2) and each altitudinal zone separately (Fig. 3). The last
two zones were combined in one graph because the number of
sites at each zone was very limited. At the zones ZER and MID
as well as when all sites are analysed together, the curves are
asymptotic and sampling may therefore be considered as
saturated. At the zones LOW and TOP-PEAK a plateau of
species numbers is roughly reached. In all cases there is a
decrease in standard deviation of the number of species as
the number of sites increases (SDALL SITES ¼ 4.97–0.48;
SDZER ¼ 5.22–1.02; SDLOW ¼ 7.86–1.61; SDMID ¼ 5.82–
1.15; SDTOP-PEAK ¼ 4.93–2.12).
Species richness at sites along the altitudinal gradient is
presented in Fig. 4 and shows a hump-shaped decline with
altitude, which may be described by a quadratic equation.
Pearson’s correlation indicates a significant negative correlation between the two variables (R ¼ )0.738, P < 0.001). The
highest numbers of species are recorded at the sites between
400 and 700 m. Species numbers decline continuously after
1000 m altitude, and they fall abruptly after 2000 m to three or
four species per site.
Species richness of Gnaphosidae was tested against the five
altitudinal zones and the three mountain massifs (anova,
Table 3). Differences are significant among altitudinal zones,
1
Poecilochroa senilis is nevertheless recorded from other lowland sites
not included in this study. Similarly S. scutulatus is recorded from
Gavdos island, south of Crete.
817
M. Chatzaki et al.
Table 2 Species composition of the family Gnaphosidae for
each altitudinal zone on Crete
60
Anagraphis pallens
Berinda amabilis
Berinda ensigera
Berlandina plumalis
Callilepis cretica
Camillina metellus
Cesonia aspida
Cryptodrassus creticus
Drassodes lapidosus
Drassodes lutescens
Drassodes oreinos
Drassodes serratichelis
Drassyllus praeficus
Drassyllus pumiloides
Drassyllus sp.
Gnaphosa bithynica
Haplodrassus creticus
Haplodrassus dalmatensis
Haplodrassus minor
Haplodrassus signifer
Leptodrassus albidus
Leptodrassus femineus
Leptodrassus hadjissaranti
Leptodrassus manolisi
Leptodrassus pupa
Micaria albovittata
Micaria coarctata
Micaria dives
Micaria pygmaea
Nomisia excerpta
Nomisia ripariensis
Nomisia sp.
Poecilochroa senilis
Pterotricha lentiginosa
Scotophaeus peninsularis
Scotophaeus scutulatus
Setaphis carmeli
Synaphosus palearcticus
Synaphosus trichopus
Trachyzelotes adriaticus
Trachyzelotes barbatus
Trachyzelotes lyonneti
Trachyzelotes malkini
Zelotes caucasius
Zelotes creticus
Zelotes daidalus
Zelotes cf. ilotarum
Zelotes labilis
Zelotes minous
Zelotes nilicola
Zelotes scrutatus
Zelotes solstitialis
Zelotes subterraneus
Zelotes tenuis
818
ZER
+
+
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LOW
+
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MID
+
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TOP
PEAK
+
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+
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30
20
0
0
5
10
15
20
25
30
35
Number of sites
+
+
+
+
+
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+
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+
+
+
+
+
+
+
+
+
+
Figure 2 Species collector curve. Data points represent average
species numbers (from 100 replicates) computed for the given
number of sites.
but not among mountain massifs. Species numbers at the sites
of each mountain massif are shown in Fig. 5. A quadratic
equation may describe the species richness decline in
Psiloreitis. In the other two mountains, regression cannot
be described by a similar equation, despite the significantly
negative correlation between number of species and altitude.
Activity
+
+
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+
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40
10
+
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+
Number of species
50
Species name
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+
Mean activity of the family as a whole is not correlated with
altitude (Pearson’s correlation R ¼ )0.083, P ¼ 0.323, Fig. 6).
However, when the sum of means of all species is divided by
the number of species present at each site, Pearson’s correlation becomes significant (R ¼ 0.645, P < 0.001). Contrary to
species richness, mean activity per species is positively
correlated with altitude (Fig. 7).
There are no significant differences in family activity among
altitudinal zones or among mountain massifs (Table 3). The
interaction of the two factors is not significant. Therefore sites
of the study area can be treated as a uniform geographical
area.
About half of the species (46%) present their maximum
activity [or potential midpoint, sensu Grytnes & Vetaas (2002)]
at the first zone, although many of them have a wide
altitudinal range (see next paragraph, and Fig. 8). Testing the
25 most abundant species separately, the mean activity of most
of them is not significantly different at the five zones (Table 4).
Four species show significant differences in their mean activity
(i.e. A. pallens, D. oreinos, P. lentiginosa and Z. tenuis). Two of
them present their maxima at higher altitudes above 1000 m
and are quantitatively more concentrated at these elevations
than the rest of the species.
Range of distribution
+
Because there is no significant effect of the regional variation
on either species richness or activity (Table 3), analysis on the
range of altitudinal distribution was conducted without taking
into account regional subdivision.
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Altitudinal distribution of ground spiders
LOW
35
Number of species
Number of species
ZER
50
45
40
35
30
25
20
15
10
5
0
30
25
20
15
10
5
0
0
2
4
6
8
10
12
14
16
0
2
4
MID
Number of species
Number of species
25
20
15
10
5
0
2
4
6
8
10
8
10
30
25
20
15
10
5
0
0
2
4
Number of sites
6
Number of sites
Table 3 Two-way anova test for the comparison of mean values
of species richness and activity of Gnaphosidae between sites
belonging to different altitudinal zones and different mountain
massifs (* ¼ significant at a ¼ 0.05)
25
y = –5E-06x2 + 0.0044x + 17.601
2
R = 0.7194
20
Number of spp
10
35
30
0
8
TOP-PEAK
35
Figure 3 Species collector curve for each
altitudinal zone separately. Data points represent average species numbers (from 100
replicates) computed for the given number of
sites.
6
Number of sites
Number of sites
15
10
5
0
0
500
1000
1500
2000
2500
Region (d.f. ¼ 2)
Altitude (d.f. ¼ 4)
Interaction (region ·
altitude, d.f. ¼ 6)
Species richness
Activity
F
P-value
F
P-value
0.98
4.38
0.507
0.393
0.017*
0.796
1.712
0.656
0.79
0.207
0.589
0.589
Altitude (m)
Figure 4 Correlation graph of the number of Gnaphosidae species at the sites along the altitudinal gradient of Cretan mountains.
The Pearson’s correlation coefficient is significant (R ¼ )0.738,
P < 0.001). The quadratic equation is also statistically significant
(R2 ¼ 0.629, F2,28 ¼ 23.72, P < 0.001).
In total, species that occur only at low (up to 500 m, 17%)
or mid-elevations (up to 1000 m, 30%) represent about half of
the total fauna of this family (Fig. 8)2. The following two zones
are the elevational limit for nine and 153 species (17% and 28%
of the total number of species respectively). Of the five species
which reach the last zone, three have a wide altitudinal range
(from sea level to 2400 m) and two present a narrower range.
In total, 14 species were found at a single zone and another
15 were found at two (26–28% of the total number of species
for each case). The remaining species were found in more than
two altitudinal zones, showing a greater range of altitudinal
tolerance. As seen in Fig. 9, altitudinal range of species is
2
In this figure, discontinuities of the altitudinal range of distribution (see Table 2) were not taken into account.
3
In the zone 1500–1999 m, there is a sampling gap between 1650
and 1950 m, so that the limits of the altitudinal range of the species
recorded here are not necessarily the highest limit for this zone.
However, four of the above species (H. dalmatensis, P. lentiginosa,
Z. caucasius and M. coarctata) were found at 1800 m as well (data not
included in this analysis).
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
positively correlated with altitude following a statistically
significant linear equation (F1,54 ¼ 15.1, P < 0.001).
Multivariate analyses
Multidimensional scaling
Ordination of sites using Bray–Curtis distance on binomial
data is seen in Fig. 10 (stress ¼ 0.13). Sites in black circles
belong to the highest altitudinal zone and are clearly
separated from the rest of sites. Apparently this ordination
is mainly caused by the two mountain species D. oreinos and
G. bithynica, which appear only at the sites of higher
elevations and by the absence of most of the rest of species
(see Appendix 2). Sites belonging to the other zones are
arranged in clusters of close vicinity, one after the other,
indicating a gradual replacement of species along the
altitudinal gradient.
Cluster analysis
For the calculation of similarity within and between sites
of each mountain massif, Jaccard’s index was used. In the
dendrograms created by cluster analysis (UPGMA) (Fig. 11)
five main clusters are observed at the level of 0.46–0.49
similarity:
819
M. Chatzaki et al.
Lefka Ori
25
24
22
20
Individuals/100 trapdays
Number of species
20
18
16
14
12
10
8
6
15
10
5
4
2
0
0
250
500
750
1000
1250
1500
1750
2000
2250
0
2500
0
500
1000
Altitude (m)
Psiloreitis
22
20
Number of species
2000
2500
Figure 6 Sum of mean activity of Gnaphosidae species (total
number of individuals per 100 trap days) along the altitudinal
gradient of Cretan mountains. Pearson’s correlation coefficient is
not significant (R ¼ )0.083, P ¼ 0.323).
24
18
16
14
12
10
3
8
6
2
0
0
250
500
750
1000
1250
1500
1750
2000
2250
2500
Altitude (m)
Dikti
24
22
20
18
16
14
12
10
8
6
4
2
0
Individuals/100 trapdays
2.5
4
Number of species
1500
Altitude (m)
2
1.5
1
0.5
0
0
500
1000
1500
2000
2500
Altitude (m)
Figure 7 Mean activity of Gnaphosidae species (total number of
individuals per 100 trap days divided by the number of species at
each site) along the altitudinal gradient of Cretan mountains.
Pearson’s correlation coefficient is significant (R ¼ 0.645,
P < 0.001).
0
250
500
750
1000
1250
1500
1750
2000
Altitude (m)
2500
Maximum activity
2000
Altitudinal zone (m)
Figure 5 Species richness of Gnaphosidae at the sites of the three
main mountain massifs of Crete. Regression analysis shows that a
quadratic equation is statistically significant only for the sites of
Psiloreitis (R2 ¼ 0.812, F2,10 ¼ 21.62, P < 0.001). Pearson’s correlation coefficient at all three mountains is statistically significant
(RLO ¼ )0.637, P ¼ 0.033; RPSI ¼ )0.866, P < 0.001;
RDIKT ¼ )0.642, P ¼ 0.031).
1500
1000
500
(a) Most of the sites of the first (0–499 m or ZER) and some of
the sites of the second zone (500–999 m or LOW), belonging
to the mountains Psiloreitis and Dikti.
(b) Sites of the third (1000–1499 m or MID) and most of the
sites of the second zone, belonging to the same mountains.
This cluster also includes one site from Lefka Ori at 1200 m
(lo1200).
(c) Sites lo50, psi50 and psi1200 with no obvious regional or
altitudinal association.
(d) Sites of the fourth zone (1500–1999 m or TOP).
(e) Sites of the fifth zone (2000–2400 m or PEAK).
820
0
0
5
10
15
20
25
30
Species rank
35
40
45
50
55
Figure 8 Altitudinal range of Gnaphosidae species along the
altitudinal gradient of Cretan mountains.
It is noteworthy that sites of Lefka Ori usually remain
outside the main clusters (for instance lo800, lo20, lo30).
Although an analysis on the effect of habitat type on the sites
ordination could not be performed, because it is correlated
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Altitudinal distribution of ground spiders
Species
ZER
LOW
MID
TOP
PEAK
P-value
A. pallens
C. creticus
C. metellus
C. cretica
D. lapidosus
D. lutescens
D. oreinos
D. praeficus
D. pumiloides
D. serratichelis
H. creticus
H. dalmatensis
M. albovittata
M. coarctata
N. excerpta
P. lentiginosa
T. adriaticus
T. malkini
Z. caucasius
Z. creticus
Z. cf. ilotarum
Z. labilis
Z. scrutatus
Z. subterraneus
Z. tenuis
0.286
0.151
0.195
0.082
0.037
0.167
0
0.318
0.050
0.025
0.041
0.095
0.040
0.287
0.753
1.012
0.155
0.610
1.363
0.476
0.081
0.678
0.518
1.308
1.427
0.100
0.515
0.068
0.038
0.170
0.379
0
1.121
0.123
0
0.167
0.012
0.036
0.112
0.509
1.433
0
0.630
0.780
0.095
0.216
0.528
0.331
0.836
1.596
0.027
0.658
0.040
0.034
1.434
0.274
0.257
2.613
0.100
0.040
0.371
0.133
0.010
0.056
0.553
4.418
0.030
0.218
0.687
0.477
0.358
0.206
0.043
0.425
0.193
0.105
1.395
0
0
0
0.045
1.528
0.533
0.027
0.042
0.550
0.160
0
0.074
0.275
4.274
0.080
0
1.761
0.143
0.000
0.630
0.027
0.590
0
0
0
0
0
0
0
2.672
0
0
0
0
0
0
0
0
0
0
0
0
0.266
0
1.181
0
0.383
0
0.000*
0.120
5.990
7.300
0.260
4.220
0.000*
0.300
3.040
5.830
1.740
6.270
7.100
2.150
4.800
0.010*
8.570
1.250
3.440
7.750
5.920
2.550
0.280
2.150
0.030*
gradient on Crete, in addition to the historical events that
contributed to the formation of this fauna, the insular
character of the study area, and the effect of human activities
on the island. Arguments for this effect, on each of the main
issues of this study, are given below.
Community structure
Along the altitudinal gradient of Crete, two main patterns of
community structure are evident: (1) that of the first zone,
from sea level to 1500 m, where there are many species with
similar activity, thus forming a well balanced fauna, and (2)
that of the higher zone, above 1600 m, where the number of
species declines considerably and very few species dominate. In
between these two zones, there is an intermediate transitional
zone, which in a stricter sense, extends further up to 2000 m,
leaving the summits forming an extreme community. As
shown by MDS (Fig. 10) and by cluster analysis (Fig. 11) this
3000
2500
Altitudinal range(m)
Table 4 Mean activity per zone of the 25 most abundant
Gnaphosidae species occurring at least along three altitudinal zones.
P-values (after Bonferroni correction for multiple comparison) of
the anova test (d.f. ¼ 4, 28; * ¼ significant at a ¼ 0.05)
2000
1500
1000
500
y = 0.5353x + 618.22
2
R = 0.2186
0
0
DISCUSSION
Gnaphosidae is one of the most diverse and the most abundant
of the spider families on the ground floor in Crete and in
Mediterranean habitats in general. This is documented in all
arachnological studies in the area (Christophe, 1974; Assi,
1986; Deltshev & Blagoev, 1994; Urones et al., 1995; Chatzaki,
1998; Chatzaki et al., 1998; Majadas & Urones, 2002; Lymberakis, 2003). Most species show a large distribution area, and
they are more diverse in temperate climates and arid ecosystems. In these environments most species have wide ecological
preferences forming quite homogenous communities, not
strongly related to habitat types.
On Crete, most Gnaphosidae are xerophilous or present
high tolerance to high temperatures and aridity and very few
have narrower, more specialized niche (Chatzaki, 2003).
Therefore, most species are widespread along the island,
despite its high heterogeneity in most ecological features
(i.e. climate, humidity, geology, vegetation, and especially
geomorphology). Similarly, the character of this family, as
described above, greatly affects its response to the altitudinal
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
1000
1500
2000
2500
Altitude(m)
Figure 9 Altitudinal range of Gnaphosidae species along the
altitudinal gradient of Cretan mountains. Pearson’s correlation
coefficient is significant (R ¼ 0.472, P < 0.001). Linear regression
is also significant (F1,54 ¼ 15.1, P < 0.001).
ZER
LOW
PEAK
TOP
Dimension 2
with altitude (Pearson’s correlation coefficient R ¼ 0.771,
P < 0.001), differences in habitat type of these sites may
explain their isolation (see Appendix 1).
500
MID
Dimension 1
Figure 10 MDS ordination based on the Bray–Curtis dissimilarity matrix of species presence–absence. Filled circles: sites at
zone ‘PEAK’, triangles: sites at zone ‘TOP’, open circles: sites at
zone ‘MID’, filled squares: sites at zone ‘LOW’, X: sites at zone
‘ZER’.
821
M. Chatzaki et al.
dik0a
dik50
psi200a
psi200b
dik300
psi300a
si300bp
psi750
lo30
dik350
psi1000b
dik700
psi650
dik800
psi1000a
psi1000c
dik1200
dik1450
lo1200
psi1650
lo50
psi50
psi1200
lo800
dik0b
lo20
psi0
lo1650
dik1750
psi1950
lo2000
lo2400
psi2200
0.17
0.31
0.46
0.60
Coefficient
latter zone is very isolated and does not relate to any of the
other zones which form a smooth gradient of ecological
variation following the altitudinal gradient. In this sense, the
Cretan summits represent ecological islands.
From 1000 m upwards species are gradually filtered out
depending on their tolerance to high mountain harshness, and,
in most cases, they are not replaced by others. The fauna of the
two higher zones is formed by: (1) lowland species that can
hardly reach these elevations, and hence they are found at the
margins of their distributional range (mostly Mediterranean
species, i.e. A. pallens, M. coarctata, N. excerpta, T. adriaticus,
Z. caucasius, Z. scrutatus), (2) species with wide elevational
range, but with potential midpoint at higher elevations, and
hence better adapted to the Cretan mountains (mostly
endemic or palearctic species, i.e. C. cretica, D. lapidosus,
D. serratichelis, D. praeficus, H. creticus, H. dalmatensis,
P. lentiginosa, Z. creticus, Z. labilis, Z. subterraneus), and (3)
species that dominate exclusively at the higher altitudes of
Crete (D. oreinos and G. bithynica).
For Gnaphosidae, the timberline does not always play an
important role for the community structure, as the main
variation of this fauna occurs at higher elevations than 1600–
1700 m. In cluster analysis (Fig. 11), sites at these elevations
are sometimes clustered with those at lower elevations
(Psiloreitis) and sometimes with those at higher elevations
(Lefka Ori and Dikti), clearly indicating the transitional
character of the fauna at this zone. Sites at this zone share
some of the most tolerant species with the lowland sites, and
the high-altitude species with the summits.
For other spider families on Crete, which are probably more
dependent on the vegetation type of their habitat due to their
way of life and foraging, such as Linyphiidae, Salticidae and
Theridiidae, there is a better defined species replacement above
1600 m as was demonstrated by Lymberakis (2003) in a study
at Lefka Ori. At the same mountain, the effect of the timberline
is also proved for other taxa, such as isopods (Lymberakis
et al., 2004), in which it separates two almost distinct faunas,
822
0.75
a
b
c
d
e
Figure 11 Cluster analysis (UPGMA) using
Jaccard’s index of similarity among the sites
of the three mountain massifs of Crete: Lefka
Ori (lo), Psiloreitis (psi) and Dikti (dik).
as far as species composition is concerned. Accordingly, in a
similar study at the high altitudes of the Central Alps, Meyer &
Thaler (1995) concluded that the decrease in species diversity
at the timberline is more drastic in phytotrophic, than in
zootrophic and saprotrophic orders.
The reason why Gnaphosidae present a comparatively
homogenous character along the altitudinal gradient, which
changes abruptly only above 2000 m, lies in the high tolerance
of its species towards aridity and temperature extremes.
Among the spider families mentioned above, Gnaphosidae is
the only one that presents peaks of activity within the dry
season (M. Chatzaki et al., unpubl. data), the other families
emerging earlier in springtime (Chatzaki et al., 1998). At least
some species are able to modify their annual cycle on the high
mountains of Crete, with peaks of activity during the more
predictable months (August/September), so they can easily
adapt to the harsh conditions of this environment (M. Chatzaki
et al., unpubl. data). Because they live on the ground, the
change of vegetation above the timberline does not affect them
directly, but only through the decline of food availability
resulting from the reduction of habitat diversity and complexity. Moreover, some authors (Swan, 1963; Mani, 1968,
1990; Edwards, 1987) emphasize the importance of windblown organic material for the survival of organisms at zones
above the tree line. They postulate that at these elevations the
abundance of this aeolian material is much greater than the
primary productivity so as to constitute the main food
resource for alpine organisms. Swan (1963) attributed the
presence and feeding of spiders of the family Salticidae at
6700 m in Mt Everest to air-blown flies and collembolans.
Being generalist predators, Gnaphosidae, apparently, can
survive even if food quality changes, provided it is enough to
support their survival.
Cluster analysis shows that the main factor inducing faunal
similarity within mountain sites is the close vicinity and
geographical orientation of the sites. However, the overwhelming factor which induces similarity is similar elevation rather
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Altitudinal distribution of ground spiders
than close geographical location (Fig. 11). Despite their
statistical insignificance, minor differences in both, patterns
of species richness decline (Fig. 5) and species composition,
are probably related to more severe climatic conditions and the
wildness of the landscape of Lefka Ori, leading to an earlier
species decline and absence of the less tolerant species.
Species richness
The hump-shaped decline of species richness is verified for
Gnaphosidae along the Cretan mountains. The same pattern is
repeated in the Cretan flora (Lymberakis, 2003), although the
abrupt decline of species richness occurs at lower elevations
associated with the timberline. Similar results are presented in
other studies on spiders (Otto & Svensson, 1982; Bosmans
et al., 1986; McCoy, 1990) or other animals (McCoy, 1990;
Colwell & Hurtt, 1994; Rahbek, 1997; Fleishman et al., 1998;
Sánchez-Cordero, 2001; Grytnes & Vetaas, 2002; Sanders,
2002). Data on several animal taxa studied until now on Crete
such as Coleoptera (Trichas, 1996), land snails (Vardinoyannis,
1994), Isopoda (Lymberakis et al., 2004), or on mountains of
continental Greece (Sfenthourakis, 1992) are not very helpful
in revealing the pattern of species richness decline, either
because the altitudinal gradient of sites starts from mid
elevations (above 500–600 m) or because data are combined
into zones: in both cases it cannot be deduced whether there is
a linear decline of species richness or there is a peak hidden
within the first altitudinal zone.
The results of our study cannot be due to a sampling
artefact, because the study was conducted from sea level to the
highest points of the island, so no sampling error may have
occurred due to restricted elevational range of the study area
(see McCoy, 1990 and Lomolino, 2001).
Sanders (2002) attributed the peak in species richness of ants
in western US to the increase of the area at mid elevations and
to the increased overlap of species distributions at the same
elevations (or ‘mid-domain’ effect, Colwell & Lees, 2000).
McCoy (1990) and Fleishman et al. (1998) interpreted their
results on different groups of invertebrates by putting forward
two biological hypotheses: (1) the prediction that ‘ends are
bad’ because of climatic severity and predation at lower
elevations, climatic severity and resource scarcity at upper
elevations, and (2) the prediction that ‘middle is good’,
relating species richness to elevation via primary productivity,
which is considered to peak at mid elevations (Janzen, 1973;
Janzen et al., 1976). A final hypothesis that cannot be
overlooked is the extent of human disturbance at lower
elevations, which may reduce species diversity (Wolda, 1987;
McCoy, 1990; Sanders, 2002).
In the case of Cretan Gnaphosidae, species richness is
maximized at the zone 400–700 m. To them the lower end is
‘bad’ because of both the higher danger of predation and of the
human disturbance. Sites below this elevation are greatly
changed by intense urbanization, which seems to have caused a
gradual degradation of the environment even in ‘natural’
habitats. Human activities are not definitely related to species
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
reduction, as, at least for some taxa (such as land snails), they
may also introduce new species in a region (Mylonas, 1984). It
should be noted that in the present study, no habitats close to
urban regions or to cultivations were analysed. The study of
these environments might change our results in favour of a
pattern similar to the linear decline of species along altitudinal
gradients.
As mentioned previously, primary productivity does not
seem to affect very much generalist predators; therefore, the
‘middle is good’ hypothesis may not be a very robust factor in
the present study.
Concerning the mid-domain effect, one has to consider the
way of formation of the Cretan mountain fauna and the characteristics of the family under investigation. Crete is the only
insular system where such research is being carried out, all
previous studies mentioned above, referring to old continental
areas. Due to its isolation, a less balanced and perhaps
impoverished fauna is to be expected (Gillespie & Roderick,
2002), especially in mountains, where a truly alpine fauna is
actually missing and has never been established. The period of
high altitude existence on Crete is very short for enhancing the
speciation of a great number of species, confined only to them.
The exclusively high mountain species of Crete (i.e. Gnaphosa
bithynica and Drassodes oreinos), probably reflecting distributional relicts, are very few for creating a second peak of
richness at higher elevations. Therefore, there cannot exist a
clear ecotone effect, as for instance in the Pyrénées where a
peak is observed at 1100–1500 m (Bosmans et al., 1986),
because there are not two distinct faunas, meeting at an
intermediate zone to form a peak of species diversity.
At the elevations where the peak of species richness is
observed on Crete, there is an optimum of environmental
factors that involves: (1) the relaxation of intense urbanization
and agricultural activities when compared with the lowest
zone, (2) good climatic equilibrium between temperature and
humidity, and (3) greater habitat diversity and stability of
climate when compared with the higher zones. These features
make this zone the meeting point of the often opportunistic
lowland species of the coastline with the older and most
permanent residents of the island.
Wolda (1987) and McCoy (1990) argued that sampling
regimes play an important role in the outcome of such a
survey, suggesting that continuous sampling over long
periods of time may lead to a monotonic pattern of species
decline, while short-term sampling may lead to mid-elevational peaks. McCoy (1990) also admits that his own results
would favour the monotonic pattern if his sampling had been
for a longer duration. The argument here is that, in lower
elevations, climatic conditions permit wider temporal variation of species activity. Therefore, short-term sampling is
not sufficient to accumulate a high percentage of species
diversity, and so underestimates it, leading to an ‘artificial’
hump-shaped pattern. Our results show that even with longterm sampling, hump-shaped patterns define species richness,
at least when not all habitat types (including urban regions)
are investigated.
823
M. Chatzaki et al.
Activity
Mean activity of Gnaphosidae is not correlated with altitude,
contrary to the activity per species which is positively
correlated with altitude. This, in combination with the decline
of species richness along altitudinal gradients of Crete,
indicates that species which are able to reach higher altitudes
can become very active and thrive at these elevations, thus
counterbalancing the differences in species numbers among
altitudinal zones. The same phenomenon was observed in the
spiders of the Central Alps (Meyer & Thaler, 1995). Reasons
that explain this are the following:
1. Shortening of the favoured period for reproduction with
altitude produces a concentration of the activity period
towards the warmer and most predictable months, i.e. summer
and early autumn. As our data correspond to this period, it is
evident that higher numbers of individuals will be recorded,
although not throughout the year.
2. Reduction in species numbers with altitude releases
competitive interactions among the remaining, tolerant species
which then find the optimum conditions to augment their
population size (Brown et al., 1996).
3. Presence of newly appearing high-altitude species at the
higher zones (1200–1600 m), where there are still many of the
lowland representatives, causes an inflation of the total activity
of the family.
McCoy (1990) reports a negative correlation in the abundance of spiders with altitude. As he used sweep nets as
sampling method, he collected spiders from the vegetation
layer and not from the ground floor (hence not Gnaphosidae).
Apparently, these spiders are more vulnerable to change of
vegetation with altitude (see Community structure) and that is
why they are not favoured at higher elevations. Instead,
Gnaphosidae seem to be the most tolerant among other spider
families as shown in a comparative analysis on a family level at
Lefka Ori (Lymberakis, 2003). This is also reported by other
authors (Otto & Svensson, 1982) and may be due either to
competitive release or to physiological/behavioural adaptations
which allow members of this family to overcome harsh
conditions at higher elevations. Moreover, some species
become even more abundant there (see Table 4). This
ecological pattern is followed by species of some other families
that belong to the same guild (wandering spiders) such as
Lycosidae, Philodromidae and Thomisidae (Lymberakis,
2003). In all cases this is due to the new appearance of species
which occur above a certain altitude. Therefore, competitive
interaction is probably the reason for the observed patterns.
The positive correlation between activity of invertebrate taxa
and altitude is not very common on Crete, as shown in
Lymberakis (2003). The author reports a positive correlation
in some families of Coleoptera (such as Curculionidae and
Tenebrionidae), in Opiliones, Homoptera, Dictyoptera, Lepidoptera and Diptera, but a negative correlation in other
families of Coleoptera (such as Carabidae and Scarabaeidae),
in Hymenoptera and slugs. A less apparent pattern of activity is
documented for scorpions, diplopods, isopods, chilopods and
824
land snails. According to Lawton et al. (1987) …‘there is no
general tendency for species to increase in abundance at higher
elevations’, and this must be related to the many factors
contributing to this parameter, i.e. species’ physiological
tolerances on the one hand and intensity of climate’s
harshness, latitude and other local factors on the other.
Altitudinal range
Our results fully conform to Rapoport’s rule. Most of the
species present occupy a great range of altitudinal distribution
(76% more than 500 m and 46% more than 1000 m). This is
related both to wide ecological tolerances of the family analysed
here and to historical reasons, which favoured the formation of
the high-altitude fauna mainly by tolerant lowland species,
rather than by truly alpine members of the family. The latter
would represent a less thermophilous arachnofauna and would
probably have narrower altitudinal ranges. In the absence of
these species, the pattern observed by members of the family on
Crete is mainly a reflection of climate change along the
altitudinal gradient. Under these circumstances, Rapoport’s
rule remains as the only logical consequence.
CONCLUSIONS
Gnaphosidae present a rather unique character along the
altitudinal gradients of Crete. They consist of a great number
of species with wide ecological tolerances, so that they occupy
wide altitudinal ranges much more than any other spider
family in the same area. Rapoport’s rule and a hump-shaped
decline of species richness are the main characteristics of their
altitudinal distribution. Two kinds of community structure are
observed, one that characterizes lower elevations (up to
1000 m) and one that is observed at the summits. Activity of
the family as a whole does not correlate with altitude as it is
highly species-specific. The ecological profile of Gnaphosidae,
as well as historical components of the formation of the Cretan
mountains are mainly responsible for these characteristics. The
Mediterranean/insular character of the study area and the
continuous degradation, especially of the lowland areas near
the coasts, are thought to influence the composition and the
response of organisms there.
The great variety of results among studies that deal with this
topic indicates that the factors governing these phenomena are
not yet clear. Reasons which add to this controversy are the
following: use of different taxa, different latitudes at which
studies are carried out, special ecological or historical conditions prevailing at each study area, differences in sampling
method, the duration and the geographical range of the
sampling in each survey (Lawton et al., 1987; McCoy, 1990;
Lomolino, 2001). Our results add to this general idea that there
is not a single overriding factor which defines the response of
organisms to environmental gradients, but rather a combination of factors, the intensity of which depends largely on the
local conditions and the history of a region, and on the special
characteristics of each taxon.
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Altitudinal distribution of ground spiders
ACKNOWLEDGEMENTS
This work was conducted in the framework of the PhD thesis
of the first author, which was funded by the Alexander Onassis
Public Benefit Foundation and by the University of Crete. We
are grateful to colleagues of the Natural History Museum of
the University of Crete for helping in the collection and sorting
of the material, and to Dr K. Thaler and Dr B. Knoflach for
their help in the identification of species. We are also grateful
to John Murphy for linguistic revision of the manuscript.
REFERENCES
Assi, F. (1986) Recherches ecologiques sur le peuplement des
araignées d’ une garrigue du Liban, p. 186. PhD thesis,
Université de Paris IV.
Bonnefont, J.C. (1972) La Crète, étude morphologique, p. 845.
PhD thesis, Université de Paris, Lille, France.
Bosmans, R., Maelfait, J.-P. & De Kimpe, A. (1986) Analysis of
the spider communities in an altitudinal gradient in the
French and Spanish Pyrénées. Bulletin of the British Arachnological Society, 7, 69–76.
Brown, J.H. (1984) On the relationship between abundance
and distribution of species. American Naturalist, 124, 255–
279.
Brown, J.H. & Kodric-Brown, A. (1977) Turnover rates in
insular biogeography: effect of immigration on extinction.
Ecology, 58, 445–449.
Brown, J.H., Stevens, G.C. & Kaufman, D.M. (1996) The
geographical range: size, shape, boundaries, and internal
structure. Annual Review of Ecology and Systematics, 27,
597–623.
Brussard, P.F. (1984) Geographic patterns and environmental
gradients: the central-marginal model in Drosophila revisited. Annual Review of Ecology and Systematics, 15, 25–64.
Chatzaki, M. (1998) Systematics and phenology of ground living
spiders of the island group Gavdos - Gavdopoula, p. 150.
Master Thesis, University of Crete (in Greek).
Chatzaki, M. (2003) Ground spiders of Crete (Araneae,
Gnaphosidae): taxonomy, ecology and biogeography, p. 452.
PhD Thesis, University of Crete (in Greek).
Chatzaki, M., Trichas, A., Markakis, G. & Mylonas, M. (1998)
Seasonal activity of the ground spider fauna in a Mediterranean ecosystem (Mt Youchtas, Crete, Greece). Proceedings of the 17th European Colloquium of Arachnology,
Edinburgh, (ed. by P.A. Selden), 235–243. British Arachnological Society, Burnham Beeches, Bucks.
Chatzaki, M., Thaler, K. & Mylonas, M. (2002a) Ground spiders (Gnaphosidae; Araneae) of Crete (Greece). Taxonomy
and distribution. I. Revue suisse de Zoologie, 109, 559–601.
Chatzaki, M., Thaler, K. & Mylonas, M. (2002b) Ground spiders (Gnaphosidae, Araneae) of Crete and adjacent areas of
Greece. Taxonomy and distribution. II. Revue suisse de
Zoologie, 109, 603–633.
Chatzaki, M., Thaler, K. & Mylonas, M. (2003) Ground spiders
(Gnaphosidae; Araneae) of Crete and adjacent areas of
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Greece. Taxonomy and distribution. III: Zelotes and allied
genera. Revue suisse de Zoologie, 110, 45–89.
Christophe, T. (1974) Etude écologique du peuplement d’
araignées d’ une litière de châtaigneraie (forêt de Montmorency, Val d’ Oise). Publications du laboratoire de Zoologie, Ecole Normale Supérieure, Paris, 3, 1–126.
Claridge, M.F. & Singhrao, J.S. (1978) Diversity and altitudinal
distribution of grasshoppers (Acridoidea) on a Mediterranean mountain. Journal of Biogeography, 5, 239–250.
Colwell, R.K. & Hurtt, G.C. (1994) Nonbiological gradients in
species richness and a spurious Rapoport effect. The
American Naturalist, 144, 570–595.
Colwell, R.K. & Lees, D.C. (2000) The mid-domain effect:
geometric constraints on the geography of species richness.
Trends in Ecology and Evolution, 15, 70–76.
Deltshev, C. & Blagoev, G. (1994) Biotopical distribution and
seasonal activity of model species of the family Gnaphosidae
(Araneae) in Zemen gorge (SW Bulgaria). Arachnologische
Mitteilungen, 7, 20–30.
Dermitzakis, M.D. & Papanikolaou, D.I. (1981) Paleogeography and geodynamics in the Aegean area during Neogene. Annales Geologiques des Pays Helleniques, 30, 245–289
(in Greek).
Edwards, J.S. (1987) Arthropods of alpine aeolian ecosystems.
Annual Review of Entomology, 32, 163–179.
Fernandes, G.W. & Price, P.W. (1988) Biogeographical gradients in galling species richness. Oecologia, 76, 161–167.
Fleishman, E., Austin, G.T. & Weiss, A.D. (1998) An empirical
test of Rapoport’s rule: elevational gradients in montane
butterfly communities. Ecology, 79, 2482–2493.
Gillespie, R.G. & Roderick, G.K. (2002) Arthropods on islands:
colonization, speciation, and conservation. Annual Review of
Entomology, 47, 595–632.
Grove, A.T., Mooney, J. & Rackham, O. (1991) Crete and the
South Aegean Islands: effects of changing climate on the
environment. Robinson College, Oxford, 445 pp.
Grytnes, J.A. & Vetaas, O.R. (2002) Species richness and altitude: a comparison between null models and interpolated
plant species richness along the Himalayan altitudinal gradient, Nepal. The American Naturalist, 159, 294–304.
Hagvar, S. (1976) Altitudinal zonation of the invertebrate
fauna on branches of birch (Betula pubescens Ehrh). Norwegian Journal of Entomology, 23, 61–74.
James, F.C. & McCulloch, C.E. (1990) Multivariate analysis in
ecology and systematics: panacea or Pandora’s box? Annual
Review of Ecology and Systematics, 21, 129–166.
Janzen, D.H. (1973) Sweep samples of tropical foliage insects:
effects of season, vegetation types, elevation, time of day,
and insularity. Ecology, 54, 687–708.
Janzen, D.H., Ataroff, M., Farinas, M., Reyes, S., Rincon, N.,
Soler, A., Soriano, P. & Vera, M. (1976) Changes in the
arthropod community along an elevational transect in the
Venezuelan Andes. Biotropica, 8, 193–203.
Krebs, C.J. (1998) Ecological methodology, 2nd edn. AddisonWesley, Longman Inc. Publishers, Benjamin/Cummings,
NY.
825
M. Chatzaki et al.
Lawton, J.H., MacGarvin, M. & Heads, P.A. (1987) Effects of
altitude on the abundance and species richness of insect
herbivores on bracken. Journal of Animal Ecology, 56, 147–
160.
Le Pichon, X. & Angelier, J. (1981) The Aegean Sea. Philosophical Transactions of the Royal Society of London, 300, 357–
372.
Lomolino, M.V. (2001) Elevation gradients of species-density:
historical and prospective views. Global Ecology and Biogeography, 10, 3–13.
Lymberakis, P. (2003) Altitudinal differentiation of the fauna of
Lefka Ori, Crete, p. 233. PhD thesis. University of Athens (in
Greek).
Lymberakis, P., Mylonas, M. & Sfenthourakis, S. (2004) Altitudinal variation of oniscidean communities on Cretan
mountains. The biology of terrestrial isopods, V. Proceedings
of the 5th International Symposium on the Biology of
Terrestrial Isopods, Crustaceana Monographs, 2 (ed. by,
S. Sfenthourakis, P.B. de Araujo, E. Hornung, H. Schmalfuss,
S. Taiti and K. Szlavecz), pp. 217–230. Brill, Leiden–Boston.
MacArthur, R.H. (1972) Geographical ecology: patterns in the
distributions of species. Harper & Row, New York.
Maelfait, J.P. & Baert, L. (1975) Contribution to the knowledge
of the arachno- and entomofauna of different wood-habitats. Part I: sampled habitats, theoretical study of the pitfall
method, survey of the captured taxa. Biologisch Jaarboek
Dodonaea, 43, 179–196.
Majadas, A. & Urones, C. (2002) Communauté d’ araignées
des maquis méditerranéens de Cyticus oromediterraneus
Rivas Mart. & al. Revue Arachnologique, 14, 31–48.
Mani, M.S. (1968) Ecology and biogeography of high altitude
insects. Dr W. Junk N.V. Publisher, The Hague.
Mani, M.S. (1990) Fundamentals of high altitude biology.
Oxford & IBH Publishing, New Delhi, Bombay, Calcutta.
Maurer, R. & Hänggi, A. (1991) Katalog der Schweizerischen
Spinnen. Documenta faunistica Helvetiae, 12, 2–33.
McCoy, E.D. (1990) The distribution of insects along elevational gradients. Oikos, 58, 313–322.
Meulenkamp, J., Wortel, M., Van Wamel, W., Spakman, W. &
Hoogerduyn Strating, E. (1988) On the Hellenic subduction
zone and the geodynamic evolution of Crete since the late
Middle Miocene. Tectonophysics, 146, 203–215.
Meulenkamp, J.E., Van der Zwaan, G.J. & Van Wamel,
W.A. (1994) On Late Miocene to recent vertical motions in
the Cretan segment of the Hellenic arc. Tectonophysics, 234,
53–72.
Meyer, E. & Thaler, K. (1995) Animal diversity at high altitudes in the Austrian Central Alps. Arctic and alpine biodiversity: patterns, causes and ecosystem consequences (ed. by
F. Stuart, I. Chapin and C. Körner), pp. 97–108. SpringerVerlag, Berlin.
Mylonas, M. (1984) The influence of man: a special problem in
the study of the zoogeography of terrestrial molluscs on the
Aegean islands. World-wide snails. Biogeographical studies in
non-marine Mollusca (ed. by A. Solem & C.A. van Bruggen),
pp. 249–259. E.J. Brill and Dr. W. Backhuys, Leiden.
826
Otto, C. & Svensson, B.S. (1982) Structure of communities of
ground-living spiders along altitudinal gradients. Holarctic
Ecology, 5, 35–47.
Pennas, P. 1977. The climate of Crete, p. 105. PHD Thesis.
Aristotle University of Thessaloniki.
Rackham, O. & Moody, J. (1996) The making of the Cretan
landscape. Manchester University Press, Manchester &
NY, 237 pp.
Rahbek, C. (1997) The relationship among area, elevation, and
regional species richness in Neotropical birds. The American
Naturalist, 149, 875–902.
Randall, M.G.M. (1982) The dynamics of an insect population
throughout its altitudinal distribution: Coleophora alticolella
(Lepidoptera) in Northern England. Journal of Animal
Ecology, 51, 993–1016.
Sánchez-Cordero, V. (2001) Small mammal diversity along
elevational gradients in Oaxaca, Mexico. Global Ecology and
Biogeography, 10, 63–76.
Sanders, N.J. (2002) Elevational gradients in ant species richness: area, geometry, and Rapoport’s rule. Ecography, 25,
25–32.
Sfenthourakis, S. (1992) Altitudinal effect on species richness
of Oniscidea (Crustacea; Isopoda) on three mountains
in Greece. Global Ecology and Biogeography Letters, 2, 157–
164.
Stevens, G.C. (1989) The latitudinal gradient in geographical
range: how so many species coexist in the tropics. The
American Naturalist, 133, 240–256.
Stevens, G.C. (1992) The elevational gradient in altitudinal
range: an extension of Rapoport’s latitudinal rule to altitude.
The American Naturalist, 140, 893–911.
Strid, A. (1995) Desertification in the White Mountains of
Crete. A botanical study with special reference to the effects
of grazing and wildfires. Environment Research Program
1991–1994: Climatology and Natural Hazards. Desertification in the Mediterranean area, 78 pp.
Swan, L.W. (1963) Aeolian zone. Science, 140, 77–78.
Trichas, A. (1996) Ecology and biogeography of ground
Coleoptera in South Aegean (composition, temporal and biotopical variation and zoogeography of the families Carabidae
and Tenebrionidae), p. 395. PhD thesis. University of Crete
(in Greek).
Urones, C., Jerardino, M. & Barrientos, J.A. (1995) Datos
fenologicos de Gnaphosidae (Araneae) capturados con
trampas de caida en Salamanca (Espana). Revue Arachnologique, 11, 47–63.
Vardinoyannis, K. (1994) Biogeography of land snails in the
south Aegean island arc, p. 330. PhD thesis, University of
Athens (in Greek).
Whittaker, R.H. (1952) A study of summer foliage insect
communities in the Great Smoky Mountains. Ecological
Monographs, 22, 1–44.
Wolda, H. (1987) Altitude, habitat and tropical insect diversity. Biological Journal of the Linnean Society, 30, 313–323.
Wright, D.H. (1983) Species-energy theory: an extension of
species-area theory. Oikos, 41, 496–506.
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Altitudinal distribution of ground spiders
BIOSKETCHES
Maria Chatzaki’s research focuses on taxonomy and island biogeography of spiders. She is interested in recognizing the origins of
the Greek spider fauna as a result of the interplay between palaeogeography and the special characteristics of the taxa under
consideration.
Petros Lymberakis is the curator of the vertebrate collection at the NHMC. His research focuses on ecology and
biogeography of small vertebrates in the Eastern Mediterranean.
Georges Markakis is Associate Professor of Biostatistics in the Technological Education Institute of Crete. He has a PhD in
probability and fuzzy logic and has also experience in many specialized statistical methods dealing with biological and
ecological problems. He is interested in designing and applying expert systems for water management.
Moisis Mylonas is a Professor in the Department of Biology of the University of Crete and Director of the NHMC. He is
mainly interested in evolutionary island ecology and conservation ecology.
Editor: Philip Stott
Appendix 1 Sites description: code names of sites and number of samplings at each one of them (in parentheses); period of each
sampling; habitat type; altitudinal zone; number of active traps and active days for each sampling. Asterisks in the ‘Period’ column
indicate cases in which the number of active days was considered as shorter than the total duration of sampling because of snow cover
during winter time
Code names
(number of
samples/site)
l020 (4)
l030 (3)
l050 (3)
10800 (7)
l01200 (6)
l01600 (8)
Period
Habitat type
Altitudinal zone
Number of active days
Number of active traps
25/4/96–26/6/96
26/6/96–25/8/96
25/8/96–29/10/96
13/3/97–7/5/97
25/4/96–26/6/96
26/6/96–22/8/96
22/8/96–30/10/96
25/4/96–25/6/96
25/6/96–20/8/96
20/8/96–30/10/96
28/3/91–5/5/91
5/5/91–8/6/91
8/6/91–6/7/91
6/7/91–4/8/91
4/8/91–8/9/91
8/9/91–5/10/91
9/3/92–5/4/92
28/3/91–5/5/91
5/5/91–8/6/91
8/6/91–6/7/91
6/7/91–4/8/91
4/8/91–8/9/91
8/9/91–5/10/91
29/7/90–1/9/90
1/9/90–17/10/90
28/3/91–5/5/91
5/5/91–8/6/91
8/6/91–6/7/91
6/7/91–4/8/91
4/8/91–8/9/91
8/9/91–5/10/91
CP
ZER
FW
ZER
FW
ZER
P
LOW
M
MID
SS
TOP
62
59
66
55
61
57
67
54
56
69
38
34
28
28
36
27
28
38
34
28
28
36
27
35
46
39
34
28
28
35
28
18
17
16
18
9
9
9
11
15
14
33
35
36
37
35
35
25
39
37
35
38
39
37
24
24
34
34
31
37
37
40
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
827
M. Chatzaki et al.
Appendix 1 continued
Code names
(number of
samples/site)
l02000 (6)
l02400 (1)
psio (3)
psi50 (3)
psi200a (4)
psi200b (2)
psi300a (3)
psi300b (3)
psi650 (2)
psi750 (2)
psi1000a (3)
psi1000b (3)
psi1000c (2)
psi1200 (2)
psi1650 (4)
psi1950 (4)
psi2200 (2)
diktoa (3)
diktob (3)
828
Period
Habitat type
Altitudinal zone
Number of active days
Number of active traps
29/7/90–1/9/90
1/9/90–16/10/90
SS
PEAK
35
45
32
34
29
29
34
29
35
61
60
67
60
60
67
75
70
54
57
71
63
71
63
65
65
67
66
52
69
52
69
54
69
63
54
69
63
52
69
89
70
78
75
45
80
78
75
45
80
47
60
61
63
62
62
79
61
28
27
28
28
8
14
14
14
10
10
10
16
16
13
16
20
20
19
18
19
18
18
18
19
20
18
18
17
17
19
19
20
20
16
17
19
19
12
15
14
14
18
17
17
18
14
14
20
19
20
17
19
16
8/6/91–6/7/91
6/7/91–4/8/91
4/8/91–7/9/91
7/9/91–6/10/91
29/7/90–1/9/90*
25/4/96–25/6/96
25/6/96–26/8/96
26/8/96–31/10/96
25/4/96–25/6/96
25/6/96–26/8/96
26/8/96–31/10/96
22/4/00–6/7/00
6/7/00–14/9/00
14/9/00–7/11/00
12/3/01–8/5/01
20/4/99–30/6/99
30/6/99–1/9/99
24/2/99–20/4/99
20/4/99–30/6/99
30/6/99–1/9/99
16/3/99–20/5/99
20/5/99–26/7/99
26/7/99–30/9/99
19/4/99–10/6/99
10/6/99–18/8/99
19/4/99–10/6/99
10/6/99–18/8/99
16/4/99–9/6/99
9/6/99–17/8/99
17/8/99–19/10/99
16/4/99–9/6/99
9/6/99–17/8/99
17/8/99–19/10/99
19/4/99–10/6/99
10/6/99–18/8/99
22/4/99–20/7/99
20/7/99–29/9/99
14/4/00–2/7/00
2/7/00–14/9/00
14/9/00–30/10/00
24/3/01–12/6/01
14/4/00–2/7/00
2/7/00–14/9/00
14/9/00–30/10/00
24/3/01–12/6/01
15/9/00–31/10/00
31/10/01–13/6/01*
26/3/99–26/5/99
26/5/99–28/7/99
28/7/99–28/9/99
3/3/99–4/5/99
4/5/99–22/7/99
22/7/99–22/9/99
SS
M
PEAK
ZER
CP
ZER
IP
ZER
IP
ZER
FW
ZER
FW
ZER
IP
LOW
IP
LOW
M
MID
IP
MID
M
MID
IP
MID
SS
TOP
SS
TOP
SS
PEAK
CP
ZER
FW
ZER
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
Altitudinal distribution of ground spiders
Appendix 1 continued
Code names
(number of
samples/site)
dikt50 (3)
dikt300 (3)
dikt350 (2)
dikt700 (3)
dikt800 (2)
dikt1200 (2)
dikt1450 (2)
dikt1750 (2)
Period
Habitat type
Altitudinal zone
Number of active days
Number of active traps
6/4/97–2/6/97
2/6/97–7/8/97
7/8/97–10/10/97
21/4/00–12/7/00
12/7/00–11/10/00
9/3/01–6/5/01
4/5/99–23/7/99
23/7/99–23/9/99
15/4/99–8/6/99
8/6/99–4/8/99
4/8/99–28/9/99
5/5/99–23/7/99
23/7/99–23/9/99
26/5/99–28/7/99
28/7/99–28/9/99
11/5/00–5/8/00
5/8/00–2/10/00
11/5/00–5/8/00
5/8/00–2/10/00
M
ZER
IP
ZER
IP
ZER
IP
LOW
IP
LOW
IP
MID
SS
MID
SS
TOP
57
66
64
82
91
58
80
61
54
57
55
79
61
63
62
85
59
85
59
14
14
14
10
13
8
20
18
19
18
18
18
17
19
19
14
14
15
15
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
829
830
A. pallens
B. amabilis
B. ensigera
B. plumalis
Cal. cretica
Cam. metellus
Ces. aspida
Crypt. creticus
D. lapidosus
D. lutescens
D. oreinos
D. serratichelis
D. pumiloides
D. praeficus
G. bithynica
H. creticus
H. dalmatensis
H. minor
H. signifer
L. albidus
L. femineus
L. hadjissaranti
L. manolisi
L. pupa
M. albovittata
M. coarctata
M. dives
M. pygmaea
N. excerpta
N. ripariensis
P. senilis
P. lentiginosa
S. peninsularis
S. scutulatus
S. carmeli
S. palearcticus
S. trichopus
0.10
0.45
0
0
0.21
0
0.23
0
0
0.27
0
0
0
0
0
0.10
0.30
0
0
0
0.09
0
0
0
0
0.20
0
0
2.09
0
0
1.08
0.09
0
0
0
0
20
LO
0.19
0
0.30
0
0
0.19
0
0
0.19
0
0
0
0
0.55
0
0
0.55
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.19
0
0
0
0
0
30
0.23
0.20
0.24
0
0
0
0
0
0.34
0.74
0
0
0
0.56
0
0
0
0
0
0
0
0
0
0
0
0.49
0
0
2.31
0
0
0.14
0
0
0
0
0
50
0
0.50
0
0
0
0.24
0.23
0
0.43
0
0
0
0.12
0
0
0.41
0
0
0
0
0
0
0
0
0
0
0
0
1.09
0
0
0.10
0
0
0.23
0
0
0
0
0
0
0.22
0
0.21
0
0
0
0.31
0
0.10
0
0
0.10
0
0
0
0
0
0
0
0
0
0
0
0
0.28
0
0
2.99
0
0
0
0
0
0
0
0
0
2.53
0
0
0
0
0
0.28
0.17
0
0
1.62
0.98
0
0
0
0
0
0
0
0
0
0.14
0
0
0.20
0
0
2.86
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
5.09
0
0
0
3.29
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1.04
0
0
0
0.52
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.23
0.30
0
0
0.24
0
0.61
0
0
0
0
0
0
0
0
0
0.12
0
0
0
0
0
0
0
0
0.60
0
0
0.12
0.12
0
0
0
0
0
0
0
800 1200 1600 2000 2400 0
PSI
0.33
0.33
0
0
0.49
0
0
0
0
0.17
0
0.17
0
0
0
0.17
0
0
0
0
0
0
0
0
0.17
0.58
0
0
2.83
0.50
0
2.99
0
0
0.50
0
0
50
0.24
0
0
0
0.46
1.42
0
0
0
0.41
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.08
0
0
0.61
0
0
4.50
0
0
0
0
0
0.15
0.07
0
0
0.16
0.22
0
0
0
0.07
0
0.07
0
0.07
0
0
0
0
0
0
0
0.08
0
0
0
0.14
0
0
0.36
0.07
0
1.97
0
0
0
0
0
0.40
0
0
0
0.21
0
0
0
0
0.15
0
0
0.37
1.04
0
0
0
0
0
0
0
0
0.07
0
0.22
0.07
0
0
0.15
0.07
0
0.08
0
0
0
0
0.53
0.4 1
0
0
0
0
0
0
0
0
0.08
0
0
0
1.91
0
0
0
0
0
0
0
0.08
0.08
0.08
0.17
1.33
0
0
0.38
0
0
0.84
0
0
0.09
0
1.51
0.12
0
0
0
0.48
0.09
0
0
0
0.14
0
0
0.07
0.71
0
0.10
0
0
0
0
0.07
0
0
0
0
0.36
0
0
0.87
0
0.10
2.55
0
0
0
0
0
0.08
0
0
0
1.17
0.08
0
0.11
0.09
0
0
0
0.09
1.28
0
0
0
0
0
0.11
0.75
0
0
0.08
0.21
0
0.21
0
0.47
0.08
0
2.81
0
0
0
0
0
0
0
0
0
0.86
0
0
0
4.72
0
0
0
0.26
8.12
0
1.96
0
0
0
0
0
0
0
0
0
0.26
0.09
0
0.51
0
0
2.87
0
0
0
0
0
0.23
0
0
0
0.07
0
0
0
0
0.29
0
0
0
1.46
0
0
0
0
0
0
0.08
0
0
0
0
0.07
0.19
0
0.20
0
0
1.73
0
0
0.10
0
0.38
0
0
0
0
0.09
0.24
0
0
0.09
0.82
0
0.12
0.24
0.52
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.48
0
0
0.24
0
0
0
0
0
0.08
0
0
0
0.38
0
0
0
0.24
0.24
0
0.12
0
4.20
0
0
0.57
0
0.24
0
0
0
0
0
0.06
0
0
0
1.66
0
0
5.86
0
0
0
0.06
0
0.11
0
0
0
2.91
0
0
0
0
0.18
1.17
0
0.11
2.13
0
1.22
0
0
0
0
0
0
0
0
0
0
0
0
0.90
0
0
4.24
0
0
0
0
0
0.31
0
0
0
0.14
0
0
0
0
0
2.65
0
0
0
1.82
0
0.64
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2.84
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1.89
0
0
0
0.41
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.453
0.58
0
0
0
0
0
0
0
0.167
0
0
0.081
0
0
0
0
0
0
0
0
0
0
0.161
0
0.163
0
0
0.329
0
0
0.1655
0
0
0
0
0
200a 200b 300a 300 b 650 750 1000a 1000b 1000c 1200 1650 1950 2200 0a
DIK
0.12
0
0.27
0
0.12
0
0
0.08
0
0.07
0
0
0
0
0
0.09
0.36
0
0
0.07
0
0.08
0
0
0
0.07
0
0.09
0
0.27
0
0
0
0
0
0
0
0b
0.32
0.11
0
0
0.22
0.76
0.18
0
0
0.13
0
0.11
0.13
0
0
0
0
0
0
0
0
0
0
0
0
0.11
0
0
0.54
0
0
0.34
0
0
0.13
0
0
50
0.52
0
0
0
0
0.15
0.12
0.12
0
0
0
0
0.12
0.26
0
0.22
0
0
0
0
0
0
0
0
0
0.10
0
0
0.56
0
0
1.76
0
0
0
0
0
0.30
0
0
0
0
0
0
0
0
0.09
0
0
0
0.06
0
0
0
0
0
0
0
0
0
0
0
0.09
0
0
0.28
0
0
0.13
0
0
0
0
0
0.17
0
0
0
0.40
0
0
0
0.34
1.66
0
0
0.24
1.66
0
0.49
0
0.10
0
0.10
0.10
0
0
0
0
0.10
0.10
0
0.33
0
0
1.34
0
0
0
0
0
0
0
0
0.98
0
0
0
0.15
0.19
0
0
0.21
1.62
0
0
0.07
0
0
0
0.07
0
0
0
0
0.14
0
0
0.10
0
0
0.07
0
0.07
0
0
0
0.08
0
0
0
0.75
0
0
0
3.14
0.59
0.51
0
0
2.01
0
0.08
0.08
0
0
0
0
0
0
0
0
0.08
0
0
0.17
0
0
5.91
0
0
0
0
0
0
0
0
0
1.66
0
0
0
0.42
0
0.73
0
0
0.84
0
0.08
0.14
0
0.17
0
0
0
0
0
0
0
0.42
0
0.23
0
0
8.65
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2.01
0
0
0
0.95
0
0
0
0
0
0
0
0
0
0
0.16
0
0
0
0
0
7.15
0
0
0
0
0
300 350 700 800 1200 1450 1750
Appendix 2 Mean number of individuals per 100 trap days at each site of the study area. Sites are coded by mountain massif (LO, Lefka Ori; PSI, Psiloreitis; DIK, Dikti) and by altitude
M. Chatzaki et al.
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
T.
T.
T.
T.
Z.
Z.
Z.
Z.
Z.
Z.
Z.
Z.
Z.
Z.
Z.
Z.
adriaticus
barbatus
lyonneti
malkini
aerosus
caucasius
cf. ilotarum
creticus
daidalus
labilis
minous
nilicola
scrutatus
solstitialis
subterraneus
tenuis
0
0
0
0
0
0.97
0
0
0.14
0.61
0
0
0.18
0
3.31
0.46
0
1.22
0.19
0
0
0.37
0.50
0
0
0.19
0
0
0.77
0
0
1.65
0.34
0
0
1.85
0
0.57
0
1.25
0
0
0
0
0.14
0
0.96
3.25
0
0.18
0
0.15
0
0.13
0
0.57
0.14
0.33
0.12
0
0
0
2.18
1.70
0
0
0
0
0
0.33
0
1.94
0
0.18
0
0
0
0
0
0.21
0
0
0
0
0
0.95
0
0.57
0
0.30
0
0
0
0
0
0
0
0
0
0
0
0
0
0.80
0
0.96
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2.59
0
0
0
0
0
0
0
0.12
0
0.53
0
0.12
0
0.84
0
0
0
0
0
0
0
1.26
1.83
0
0
0.33
0
3.33
0
2.75
0
0.67
0
0
1.17
0
2.84
0.50
0
0
0.08
0.52
0
0.63
0
0
0.25
1.51
0.17
0
0.81
0.09
2.28
1.32
0
0
0.07
0.49
0
4.71
0
0
0.14
1.42
0
0
1.37
0.08
0.28
0.47
0
0
0
1.38
0
3.56
0
1.83
0.07
1.06
0
0
0.44
1.21
1.90
2.62
0
0
0.37
0.33
0
1.08
0.63
0
0.08
2.32
0
0
1.25
1.43
0.78
1.17
0
0
0
0.39
0
1.17
0
0
0
0.84
0
0
0.31
0
0.20
2.61
0
0
0
0.52
0
1.19
0
0
0.08
0.48
0
0
0.45
0.08
0.53
0.24
0
0
0
0.15
0
1.46
0
0
0
0.18
0
0
0
0
0.29
0.17
0
0
0
0.28
0
0.68
0.77
0
0
0.43
0
0
0.96
0
0.47
0.75
0
0
0
0.60
0
0.17
0
0
0
0.09
0
0
0
0
0.51
0.78
0.18
0
0
0
0
1.27
0
0.92
0
0.13
0
0
0.18
0
0.37
0
0.32
0
0
0
0
0.30
0
0
0
0.44
0
0
0.11
0
0.84
0
0
0
0
0
0
0.82
0
0
0
0.91
0
0
0
0
1.14
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1.15
0
0
0
1.5605
0.369
0
0
0
0
0
0.332
0
0
0.1235
0.241
0.322
3.528
0
0
0.62
0.20
0
0.47
0
0
0
0.13
0
0.47
0.15
0.85
0.40
0.72
0
0
0
2.08
0
0.33
0
0
0.11
0.22
0.11
0
0.22
0.11
2.94
0.99
0
0
0.12
0.45
0
2.83
0
0
0.35
0.86
0.63
0
0.56
0
1.40
0.39
0
0
0
0
0
0.13
0
0
0
0.17
0
0
0.08
0
0.90
1.66
0
0
0
1.80
0
0.81
0.53
0
0
0.68
0
0
0.19
0
0.57
3.16
0
0
0
0.63
0
0.69
0
0
0
0.40
0
0
0.07
0
1.06
1.12
0
0
0
0.17
0
0.29
2.15
0
0
0.13
0
0
0.08
0
0.25
0
0
0
0
0.39
0
0.59
0
0
0
0.54
0
0
0
0
1.13
0
0
0
0
0
0
4.97
0
0
0
0.86
0
0
0
0
0.38
0
Altitudinal distribution of ground spiders
Journal of Biogeography 32, 813–831, ª 2005 Blackwell Publishing Ltd
831