Diversity of spiders in the Alps
at different altitudes
Authors: Eva Martínková, Charles University in Prague, Czech Rep.
Salome Olsson, Uddevalla Gymnasieskola, Sweden
Susanna Vain, Tallinn English College, Estonia
Tutor:
Salome Steiner
June 2013, Valchava
Summary
Spiders are an important part of the Alpine macrofauna. There are many different types of
spiders, some of them are living on the ground and some of them in the trees. They use
different ways to catch its prey, the ground-hunting spiders grabs the food while other spiders
are building nets. The aim of this project is to compare how the number of morphospecies and
specimens varied in different altitudes in the Swiss Alps. This was carried out by investigating 2
different 10x10m squares in 3 different altitudes. Due to collected data a big differences
between altitudes can be seen. The most morphospecies were found in the middle altitude as
well as the higher number of individuals. The smallest number of morphospecies was found in
the highest altitude, as it was expected. But the smallest number of individuals was found in the
lowest altitude, which was unexpected. In general no correlation of number or morphospecies
with the altitude could be found. Some of the discussed reasons for the variations that could be
observed are habitat, weather conditions and competition.
Introduction
Spiders are one of the most abundantly found animals in the Alps, composing about 9-51% of
the macrofauna. [1] Some of the most commonly found spider families are wolf spiders
(Lycosidae), jumping spiders (Salticidae), crab spiders (Thomisidae) and orb-weavers
(Araneidae). The spiders can be found mainly on 3 places: preying on the ground, in webs or
funnels and on the plants. [2]
The wolf spiders are spiders with excellent eyesight. They hunt mostly alone on the ground,
they do not build hunting nets. They can be from 1 to 30 mm large and have 8 eyes in 3 rows.
Females carry their young in a cocoon, which is a typical pattern for them. [3]
Jumping spiders is the biggest family of spiders, it contains of about 5000 described species,
which is 13 % of all described ones. They have 6 eyes and very good eye-sight. Their legs are
short and strong, they can jump very well, what they use for hunting. They do not build nets
either, just small cocoon, where they live in. [4]
Crab spiders have a flat and wide body with the two last legs shorter. They wait for their victim
and catch it with strong front legs, without using a net. Their name comes from the way they
move – like a crab. They live on plants. [5]
Orb-weavers are the most common group of spiral net-builders. They have 8 eyes and a typical
cross on their back. They use their net for catching flying insects like flies or mosquitos, using
the signal fibre, which tells them that the victim is in the net. The nets are built between trees or
plants. [6]
In this research investigated spiders are divided into two main groups – the ones using the net
for hunting and the ones hunting on the ground. They are investigated in open patches in three
different altitudes of the subalpine zone. The aim of our project is to investigate whether the
population sizes of spiders, as well as the diversity, depend on the altitude. Smaller population
of spiders and lower diversity is expected in the high area.
1
Methods and material
The whole research took place in the Val Mora, Graubünden, Switzerland. We collected spider
at three different altitudes (Fig. 1) from the 24th to 26th of June 2013. There were two areas of
10x10 meters in every altitude chosen. For each area open country with one tree was chosen.
Figure 1: The three sampling locations in the Val Mora.
In every square some specifications were investigated. It was geology, exposition of the slope
and percentage coverage of the square with vegetation, bare soil and scree. The description of
every area is written in Tab. 1.
Table 1: The description of the 6 investigated squares.
Date of collecting
25. 6. 2013
25. 6. 2013
25. 6. 2013
26. 6. 2013
26. 6. 2013
26. 6. 2013
Place/altitude
Alp Mora
1/low
the river
1/middle
the cottage
1/high
Alp Mora
2/low
the river
2/middle
the cottage
2/high
Exposition
South
Northeast
Northeast
South
Northeast
Northeast
Degree of slope
30°
20°
15°
30°
60°
10°
Topographic
context
slope
slope
Top of the
hill
slope
Slope
Top of the
hill
Geology
Verrucano
Limestone
Limestone
Verrucano
Limestone
Limestone
10 %
35 %
40 %
15 %
35 %
50%
1%
5%
20 %
1%
5%
20 %
89 %
60 %
40 %
84 %
60 %
30 %
Cover of scree
(%)
Cover of bare soil
(%)
Cover of
vegetation (%)
The spiders were not only observed but collected because of the GEO-Tag der Artenvielfalt and
handed to A. Hänggi (Naturhistorisches Museum Basel) for further investigation (For further
questions please contact SJF). To collect spiders in the squares, three methods were used. As
the first method the traps with soapwater were used. The soap causes a lower surface tension,
so the spiders cannot escape from the traps. Traps were made from plastic cups which were put
2
into the ground. There were placed two traps in every area for two days. The traps were
checked every day.
The second method was manual collecting of spiders. The spiders were collected by three
people for half an hour in every square. They were caught into plastic tubes and then put into
ethanol. The last method was catching the spiders from all trees in the area with a net. Spiders
were also put in the tubes with ethanol and also handed to A. Hänggi (Naturhistorisches
Museum Basel).
One area of every altitude per day was investigated with the two last mentioned methods.
Spiders were then counted and assigned into two hunting groups: on the ground hunting
spiders and net-building spiders. Morphospecies were determined and also the sex was
specified on the ground hunting group.
Results
25
60
20
15
Web-spinning
spiders
10
Ground-hunting
spiders
5
0
Amount of spiders
Number of morphospecies
In total, 154 spiders were trapped and 32 different morphospecies were identified. Figure 2A
shows the number of morphospecies found at different altitudes. The results show that the
number of different morphospecies of both, web-spinning and ground-hunting spiders varies
greatly at different altitudes. The highest amount of morphospecies can be found in the middle
altitude for both, web-spinning and ground-hunting spiders. Also, it shows that for web-spinning
spiders the variance is greater than for ground-hunting spiders.
50
40
Low alt.
30
Middle alt.
20
High alt.
10
0
1
Altitude
2A
2
3
4
5
6
Morphaspecie
7
8
2B
Figure 2A: Number of morphospecies at different altitudes. Figure 2B: Reoccurring morphospecies in the
squares.
Some morphospecies were reoccurred in both squares at the three different altitudes (Fig. 2B).
In the middle altitude, the most morphospecies occurred more than once, 48 individuals from 7
morphospecies in total. These are 63.2 % of all collected spiders. In the high altitude, 59 of all
spiders belong to 3 morphospecies, which is 90.8 % of all spiders found in that area. In the low
altitude, 49 individuals belong into 5 reoccurring morphospecies, which is 89%. On the other
hand just 2 morphospecies were found in all three altitudes. The amount of the concrete spiders
depends on the altitude, which can also be seen in the graph.
3
Figure 3A shows the number of individuals of web-spinning and ground-hunting spiders found at
different altitudes. The results indicate that significantly more ground-hunting spiders were found
than web-spinning individuals. Also, the variance of numbers of specimens was smaller for the
ground-hunting spiders.
35
70
Amount of spiders
Number of individuals
80
60
50
40
Web-spinning
spiders
30
Ground-hunting
spiders
20
10
30
25
20
Female
15
Male
10
5
0
0
High Middle Low
Altitude
Low
3A
Middle
Altitudes
High
3B
Figure 3A: Amount of spider individuals at different altitudes. Figure 3B: Sex of caught ground hunting
spiders at different altitudes.
The sex of caught ground-hunting spiders was also checked. More females then males were
trapped (Fig. 3B). According to the data, the number of active females is increasing with
altitude.
5. Discussion
The greatest diversity of spiders was found in the middle altitude where it was less windy,
exposed to sun and had screes abundantly that provide habitat for ground-hunting spiders.
There were also bigger trees and shrubs on the ground that provide habitat for web-spinning
spiders. In the higher altitude, only ground-hunting spiders were caught, probably because of
the nearly lack of trees and stronger wind. In the low altitude, both hunting types were found but
it was less exposed to sun, what may cause the smaller diversity. Another explanation could be
that this low area lies in a pasture, that provide less microstructures then the middle altitude.
Also, the greater amount of scree slopes (about 10% more than in other altitudes) provides
habitat for boreal invertebrates that spiders can feed on, a possible explanation that about 14%
more ground-hunting spiders were caught in the higher altitude than in other altitudes.
2 morphospecies were found in all altitudes, indicating that they are resistant to big
environmental changes like strong wind and cold temperatures. In higher altitudes, the
specimens were also found in bigger numbers then in the other two altitudes, probably because
of less competition. However, another reason for the small number of reoccurring
morphospecies was probably the fault of limited searching time and the varying weather
conditions. Nevertheless, all together there were 8 morphospecies that were caught in both
squares in an altitude.
From the results it also appears that for ground-hunting spiders, the greater the altitude, the
more active female specimens are – in the low altitude, male and female individuals were
caught in equal numbers but as the altitude increased, more females than males were caught.
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Since in spiders, usually females are larger than males, the increasing altitudinal and hence
more extreme conditions may explain why larger specimens – i.e. the females – were more
active. [10]
During the research, the importance of weather in the activeness of spiders was noticed. In the
second day when it was warmer and less windy, more spiders were caught in all altitudes. For
example in the highest altitude 38 specimens were found the second day, compared to the first
day when only 27 specimens were found. The middle altitude also showed the same difference.
Other studies also indicate that spiders in higher altitudes prefer more sun-exposed habitats.
Another reason for the increased catching success could also be the greater experience in
catching. This could also explain why more specimens were caught in the low altitude on the
second day, even though the weather conditions did not differ that greatly in the morning when
the catching was carried out. Nevertheless, further investigations could be made concerning the
activity of spider both males and females influenced by whether conditions.
6. Acknowledgements
We would like to thank the Schweizer Jugend Forscht, who enabled this research. Another
thanks belongs to our national organizations: Národní institut dětí a mládeže ČR (NIDM ČR),
Õpilaste Teaduslik Ühing and Unga Forskare, which enabled our participation in the camp. Last
but not least we like to thank Salome Steiner for guiding and tutoring.
7. References
1) Bellmann, H. Der Kosmos Spinnenführer, Stuttgart: Franckh-Kosmos Verlags-GmbH &
Co. KG, 2010, ISBN 978-3-440-10114-8
2) Nagy, L. Alpine Biodiversity in Europe, Heidelberg: Springer, 2003, ISBN 9783642623875
3) University of California Three ways to Identify Your Spider, last accessed 24.06.2013
‹http://biokeys.berkeley.edu/inverts/spiders/›
4) Polish Journal of Ecology, last accessed 24.06.2013, ‹http://www.pol.j.ecol.cbe-pan.pl/›
5) Bowden, Joseph Fecundity and sexual size dimorphism of wolf spiders (Araneae:
Lycosidae) along an elevational gradient in the Arctic, last accessed 24.06.2013,
‹http://link.springer.com/article/10.1007%2Fs00300-013-1308-6›
6) Last accessed 24.06.2013, ‹http://map.geo.admin.ch/›
7) Wolf Spider, last accessed 24.06.2013, ‹http://en.wikipedia.org/wiki/Wolf_spider›
8) Jumping Spider, last accessed 24.06.2013, ‹http://en.wikipedia.org/wiki/Jumping_spider›
9) Crab Spider, last accessed 24.06.2013, ‹http://en.wikipedia.org/wiki/Crab_spider›
10) Orb-weaver Spider, 24.06.2013, ‹http://en.wikipedia.org/wiki/Orb-weaver_spider›
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