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Hibernation of predatory arthropods in semi-natural
habitats
Flavia Geiger ÆFelix L. Wa
¨ckers Æ
Felix J. J. A. Bianchi
Received: 4 March 2008 / Accepted: 8 December 2008 / Published online: 28 December 2008
ÓThe Author(s) 2008. This article is published with open access at Springerlink.com
Abstract Non-crop habitats provide important
resources for natural enemies. Many natural enemies
hibernate in non-crop habitats, from which they may
colonise arable fields in the spring. Spring colonisa-
tion ensures annual repopulation of the crop with
natural enemies, allowing them to keep pace with the
development of pest populations. The availability of
non-crop habitats can, therefore, be crucial to
successful conservation biological control. We quan-
tified the density of overwintering natural enemies
near organic Brussels sprout crops in five different
non-crop habitats (short grassy field margin, herba-
ceous field margin, herbaceous field margin under a
tree line, ditch and forest). Soil and litter samples of
non-crop habitats were taken at two sites. One site
was located in an open agricultural landscape, the
other in a landscape dominated by mixed forest.
Insects belonging to Staphylinidae, Araneae, Cara-
bidae, Coccinellidae and Dermaptera were the most
abundant. Mean densities of predatory arthropods
were higher in the open agricultural landscape (290
predators m
-2
) than in the forested landscape (137
predators m
-2
). Herbaceous habitat types supported
the highest densities of overwintering predators (up to
400 predators m
-2
), whereas densities in the forest
were lowest (10 predators m
-2
). These results
indicate that herbaceous non-crop habitats are
important refugia for predators and may play a vital
role in conservation biological control.
Keywords Agroecosystems Predators
Conservation biological control Overwintering
Non-crop habitat Pest control
Introduction
Habitat diversity may facilitate natural pest control in
annual arable cropping systems (Gurr et al. 2003;
Tscharntke et al. 2007). However, agricultural inten-
sification tends to lead to the simplification of
landscape composition and the reduction of habitat
diversity (Westmacott and Worthington 1997;
Manhoudt and de Snoo 2003). Non-crop habitats like
forests, hedgerows, tree lines, field margins and
ditchbanks are essential for the conservation of a
diversity of natural enemies in agricultural landscapes
Handling Editor: Arne Janssen.
F. Geiger (&)
Nature Conservation and Plant Ecology, Wageningen
University and Research Centre, P.O. Box 47,
6700 AA Wageningen, The Netherlands
e-mail: flavia.geiger@wur.nl
F. L. Wa
¨ckers
Centre for Sustainable Agriculture, Lancaster University,
L.E.C., Lancaster, UK
F. J. J. A. Bianchi
CSIRO Entomology, 120 Meiers Road, Indooroopilly,
QLD 4068, Australia
123
BioControl (2009) 54:529–535
DOI 10.1007/s10526-008-9206-5
that can play a role in suppressing pest populations in
crops (Duelli and Obrist 2003; Bianchi et al. 2006).
Non-crop habitats may provide plant-derived food
resources, e.g. nectar or pollen, alternative prey,
refuge from pesticides and other disturbances, shelter,
a moderate microclimate and hibernation sites (Landis
et al. 2000). By providing these resources, non-crop
habitats can support natural enemy populations and
help enhance their impact on pest population dyna-
mics (Wilkinson and Landis 2005).
The majority of natural enemies depends on non-
crop habitats for overwintering, as bare fields are
generally less suitable for hibernation (Andersen
1997; Pfiffner and Luka 2000). The presence of
hibernation sites near crop fields allows an effective
early season colonisation of crops, which may result
in effective pest suppression (Coombes and Sotherton
1986; Dennis and Fry 1992; Bianchi and van der Werf
2003). Especially, polyphagous predators, such as
Carabidae, Staphylinidae and Araneae, may play an
important role in pest regulation in the spring because
of their early activity and broad food range (Chiverton
1986; Chang and Kareiva 1999; Symondson et al.
2002). Besides the spatial distribution of crop and
non-crop habitats in the agroecosystem, the vegetation
structure of non-crop habitats may also play an
essential role in the winter survival of arthropods
(Dennis et al. 1994; Pfiffner and Luka 2000).
In this study, we compared different types of non-
crop habitats adjacent to Brussels sprouts fields with
respect to densities and the community structure of
overwintering predator populations. The identifica-
tion of suitable hibernation sites contributes to our
understanding of predator–prey interactions in agro-
ecosystems and may provide tools to enhance
conservation biological control.
Materials and methods
The study was conducted at two sites, Achterberg and
Wageningen-Hoog, which are located near Wagen-
ingen, the Netherlands. The site in Wageningen-Hoog
is surrounded by mixed forest, whereas the site in
Achterberg is surrounded by grassland and arable
crops. Brussels sprouts fields of approximately
800 m
2
were established at both sites. Brussels sprout
was grown under organic management in order to
exclude possible undesirable effects of synthetic
agrochemicals on natural enemy densities. The fields
were surrounded by different types of non-crop
habitats. Mowed grassy field margins and unmowed
herbaceous field margins (various herbaceous and
grassy species) occurred in both Achterberg and
Wageningen-Hoog. A herbaceous field margin under
a tree line (beech) and mixed forest was only present
in Wageningen-Hoog, while a ditchbank with tall
grass (approximately 50 cm) was only found in
Achterberg. Sampling took place in the first week
of December 2003. In each non-crop habitat, ten
samples were taken in a transect at 1-m intervals.
Samples consisted of vegetation and the upper 10 cm
of soil in quadrates of 25 925 cm
2
. In addition,
other possible hibernation sites in the forest (e.g.
under stones and under the bark of trees) were
searched visually for the presence of arthropods. The
samples were taken to the laboratory in plastic bags
and stored at 4°C until further processing. Samples
were thoroughly broken up in white trays, after which
arthropods were extracted by hand. Carabidae,
Coccinellidae and Dermaptera were identified upon
the species level. Staphylinidae and Araneae were
identified to the genus level, except for the (sub)fam-
ilies Linyphiidae and Aleocharinae, which were not
further identified.
Statistical analyses
Distributions of arthropod communities in the differ-
ent habitat types and locations were analysed using
redundancy analyses (RDA) with CANOCO 4.53 (ter
Braak and S
ˇmilauer 2002). For the analyses of group
distributions at both sites and all habitat types, we
used a scaling based on inter-sample distances. For
RDA for the individual sites, inter-species correla-
tions was used as the scaling method to reveal
differences among species. Species scores were
divided by their standard deviations. The species
data table is centred by species (i.e. species are
weighted by their variance).
Results
Staphylinidae, Araneae, Carabidae, Coccinellidae and
Dermaptera were the most abundant taxonomic groups
of natural enemies. Most specimens of Staphylinidae
belonged to the sub-family Aleocharinae and the genus
530 F. Geiger et al.
123
Tachyporus (Table 1). Linyphiidae and Bembidion
were the most common representatives of Araneae
and Carabidae,respectively. The three genera Harpalus,
Dyschirius and Amara of the Carabidae family and
the only species from the Coccinellidae family, i.e.
Tytthaspis sedecimpunctata (Linnaeus), were excluded
from the data because they are not carnivorous (Freier
and Gruel 1993; Turin et al. 2000). Dermaptera were
only represented by Forficula auricularia (Linnaeus).
Redundancy analyses indicate that habitat type and
location account for 59% of the variance of the four
major taxonomic groups (Aranaea, Staphylinidae,
Carabidae and Dermaptera; Fig. 1). Predator groups
were not evenly distributed over habitat and land-
scape type (Table 2; Fig. 1). Dermaptera were only
found in the forest-dominated site (Wageningen-
Hoog). Carabidae were more numerous in Wagenin-
gen-Hoog, but also occurred in Achterberg, whereas
Araneae and Staphylinidae were the dominant groups
in the open landscape in Achterberg. The average
predator density was higher in Achterberg (288 m
-2
)
than in Wageningen-Hoog (130 m
-2
). This trend was
also apparent in grassy and herbaceous field margins
that occurred in both Achterberg and Wageningen-
Hoog (Fig. 2). In both sites, the highest densities of
predators were found in herbaceous field margins,
followed by herbaceous field margin under a tree line
in Wageningen-Hoog and ditch in Achterberg,
respectively (Fig. 2). In grassy field margins (Ach-
terberg) and forest (Wageningen-Hoog), the lowest
densities of hibernating predators were found. No
predators were found under tree bark and stones in
the forest of Wageningen-Hoog.
In Wageningen-Hoog, Araneae and Carabidae
tended to be more abundant in the herbaceous field
margin, whereas Staphylinidae had the highest den-
sities in herbaceous field margins under a tree line
(Table 2). RDA revealed that the species within the
families of Carabidae, Staphylinidae and Araneae
were not evenly distributed over the habitat types. For
instance, two carabid species Bembidion quadrima-
culatum (Linnaeus) and B. properans (Stephens)
were strongly associated with grassy habitats,
whereas the other carabid species were most abun-
dant in the herbaceous habitats (Fig. 3). In
Wageningen-Hoog, the herbaceous field margin
showed the strongest correlation with the first (hor-
izontal) RDA axis, while herbaceous field margin
under a tree line showed the strongest correlation
with the second (vertical) axis. The three habitats
together accounted for 63% of the variance in the
group composition of Carabidae. As for Araneae, the
family Linyphiidae was strongly associated with
grassy field margins, whereas most of the other
groups were found in herbaceous field margins (data
not shown).
In Achterberg, Staphylinidae and Araneae were
most abundant in the herbaceous field margin,
whereas Carabidae were most abundant in the ditch
vegetation (Table 2). The species composition within
the three taxonomic groups also differed between the
habitat types in Achterberg. For example, almost all
genera of Araneae were most abundant in the
herbaceous field margins, except for Linyphiidae
and the genus Clubiona, which preferred the grassy
field margin (Fig. 4). The three habitat types together
accounted for 32% of the variance in the Araneae
composition. Carabid species showed a similar
distribution across habitats as in Wageningen-Hoog.
B. properans and Anisodactylus binotatus (Fabricius)
were the only species occurring in grassy field
margins, while the other species were found in
herbaceous field margins or in the ditch margin (data
not shown).
Discussion
We quantified the densities of hibernating natural
enemies in five non-crop habitats in two contrasting
landscapes. Peak densities of predators in our study
(400 predators m
-2
) were lower than in other studies,
where the densities ranged between 1,100 and 1,500
predators m
-2
(Thomas et al. 1991; Lys and Nentwig
1994; Pfiffner and Luka 2000). These differences
may reflect a variation in the predator densities
between studies, but the differences may also be
caused by different sampling and extraction methods.
As we used similar methods to Thomas et al. (1991),
i.e. 10-cm-deep soil samples and hand-sorting of
arthropods, we can conclude that the predator
densities in our study were indeed lower than in the
study by Thomas et al. (1991). This suggests that
predator densities in hibernation sites can be lower
than generally assumed.
The overall density of hibernating predators were
higher in the open agricultural landscape (Achter-
berg) as compared to the landscape dominated by
Hibernation of predatory arthropods 531
123
Table 1 Overview of Staphylinidae, Araneae, Carabidae and
Dermaptera found in Wageningen-Hoog (WH) and Achterberg
(A) in grassy field margins (GFM), herbaceous field margins
(HFM), herbaceous field margin under a tree line (TFM), forest
(F) and ditch (D). The number of specimens are indicated in
brackets
WH A
Staphylinidae Aleocharinae (146) HFM, TFM, GFM, F HFM, GFM, D
Tachyporus (Gravenhorst) (67) HFM, TFM, F HFM, GFM, D
Xantholinus (Dejean) (34) HFM, TFM HFM, GFM, D
Philonthus (Stephens) (32) TFM, F HFM, GFM, D
Gabrius
a
(Stephens) (18) HFM, TFM HFM, GFM, D
Stilicus (Berthold) (11) HFM HFM, GFM, D
Tachinus (Gravenhorst) (5) HFM, GFM, D
Conosoma (Kraatz) (3) HFM D
Stenus (Latreille) (3) D
Lathrobium (Gravenhorst) (2) D
Oxytelus (Gravenhorst) (2) HFM
Trogophloeus (Mannerheim) (1) D
Othius (Stephens) (1) TFM
Araneae Linyphiidae (125) HFM, TFM, GFM, F HFM, GFM, D
Trochosa (Koch) (26) HFM, TFM HFM, D
Pachygnatha (Sundevall) (25) HFM, TFM HFM, D
Pardosa (Koch) (24) TFM, GFM HFM, GFM, D
Alopecosa (Simon) (19) HFM HFM, D
Xysticus (Koch) (12) HFM HFM, GFM, D
Heliophanus (Koch) (11) HFM
Clubiona (Latreille) (6) HFM GFM
Pisaura (Simon) (4) TFM HFM, D
Zelotes (Gistel) (3) HFM HFM
Juveniles (31) HFM, TFM HFM, GFM, D
Carabidae Bembidion femoratum (Sturm) (2) HFM
Bembidion guttula (Fabricius) (3) HFM, D
Bembidion lampros (Herbst) (156) HFM, TFM HFM, D
Bembidion properans (Stephens) (3) GFM GFM, D
Bembidion quadrimaculatum (Linnaeus) (1) GFM
Bembidion tetracolum (Say) (30) HFM, TFM HFM
Syntomus foveatus (Geoffroy) (23) HFM HFM, D
Syntomus truncatellus (Linnaeus) (3) HFM HFM
Pterostichus strenuus (Panzer) (6) TFM D
Pterostichus vernalis (Panzer) (13) HFM, TFM HFM, D
Notiophilus biguttatus (Fabricius) (3) TFM
Notiophilus palustris (Duftschmid) (3) HFM HFM
Agonum dorsale (Pontoppidan) (2) D
Agonum muelleri (Herbst) (2) HFM
Calathus melanocephalus (Linnaeus) (3) HFM
Stenolophus teutonus (Schrank) (2) HFM, D
Anisodactylus binotatus (Fabricius) (1) GFM
Microlestes minutulus (Goeze) (1) D
532 F. Geiger et al.
123
forest (Wageningen-Hoog; Fig. 2). The higher den-
sity of predators in Achterberg may be explained by a
higher pest pressure in Achterberg (Geiger, personal
observation), which may have supported a larger
community of predators as compared to Wageningen-
Hoog. Alternatively, the lower density of non-crop
habitats in Achterberg may have resulted in a
concentration of overwintering predators in the few
non-crop habitats present.
Table 1 continued
WH A
Clivina fossor (Linnaeus) (1) D
Dermaptera Forficula auricularia (Linnaeus) (6) HFM, TFM
a
Identification is uncertain
Axis 2
Axis 1 2.5-1.5
2.0-1.5
Araneae
Staphylinidae
Carabidae
Dermaptera
WH GFM
WH HFM
WH TFM
WH F A GFM
A HFM
A D
Fig. 1 Biplot diagram of the redundancy analysis focussing on
the distribution of Araneae, Staphylinidae, Carabidae and
Dermaptera in relation to habitat types in Wageningen-Hoog
and Achterberg. The first ordination axis (axis 1) had an
eigenvalue of 0.38 and species–environment correlation of
0.85. The second ordination axis (axis 2) had an eigenvalue
of 0.21 and species–environment correlation of 0.82. WH =
Wageningen-Hoog (filled triangles), GFM =grassy field
margin (open squares), HFM =herbaceous field margin (open
circles), TFM =herbaceous field margin under a tree line
(open diamonds), F =forest (pluses), A =Achterberg
(upside-down filled triangles), HFM =herbaceous field mar-
gin (filled circles), GFM =grassy field margin (filled squares),
D ditch (crosses)
0
100
200
300
400
500
TFM
predator densitiey (m-2)
DFHFMGFM
Fig. 2 Cumulative mean densities of Carabidae, Staphylini-
dae, Araneae and Dermaptera in grassy field margins (GFM),
herbaceous field margins (HFM), herbaceous field margins
under a tree line (TFM), forest (F) and ditch (D) in
Wageningen-Hoog (filled bars) and/or Achterberg (hatched
bars). The error bars indicate the standard error of the mean
(SEM; n=10)
Table 2 Densities of arthropods (m
-2
;n=10; SEM =stan-
dard error of the mean) and proportion (%) of total predator
densities in five habitat types in Wageningen-Hoog and
Achterberg (GFM =grassy field margin, HFM =herbaceous
field margin, TFM =herbaceous field margin under a tree line,
F=forest, D =ditch)
Wageningen-Hoog Achterberg
GFM HFM TFM FMean SEM GFM HFM DMean SEM
Staphylinidae 1.6 32 40 8 20.4 0.57 48 206.4 184 146.13 3.73
Araneae 33.6 48 41.6 1.6 31.2 0.84 104 176 48 109.3 2.53
Carabidae 3.2 206.4 94.4 0 76 2.48 3.2 25.6 70.4 33.1 1.19
Dermaptera 0 4.8 4.8 0 2.4 0.17 0 0 0 0 0.00
Total 38.4 291.2 180.8 9.6 130 3.28 155.2 408 302.4 288.5 4.89
% 7.4 56 34.8 1.8 17.9 47.1 34.9
Hibernation of predatory arthropods 533
123
The five habitat types supported different densities
of hibernating predators. In this study, herbaceous
field margins and ditch vegetation supported the
highest predator densities (Table 2). These habitats
have a dense and tall vegetation cover (30–50 cm)
and may provide suitable microclimatic conditions in
winter (Dennis et al. 1994). For instance, Burki and
Hausammann (1993) demonstrated that the minimum
soil temperatures in dense weed strips were 5°C
higher than in arable fields. Predator densities in
forest edges and grassy field margins were lower than
in herbaceous habitats (Table 2). However, as these
habitats covered a much larger area than the herba-
ceous habitats, the total number of predators
hibernating in forest edges and grassy field margins
may still have been considerable. Linyphiidae were
the only predators with a clear preference for grassy
habitats. This family is active at temperatures as low
as 0.5°C and may have an improved winter cold-
hardiness as compared to most other spiders that
hibernate in herbaceous habitats (Bayram and Luff
1993).
In our study, we showed that non-crop habitats, in
particular those that contain herbaceous vegetation,
are important hibernation sites for generalist
predators. Unmanaged margins near crop fields
may, therefore, act as sources of natural enemies
that colonise arable fields in the spring. Therefore, the
establishment of non-crop habitats not only increases
the aesthetic and recreational value of agricultural
landscapes, but it may also boost biological control
and reduce the dependency on chemical pesticides.
Acknowledgments We thank I.M.A. Heitko
¨nig (Resource
Ecology Group, Wageningen University and Research Centre)
and C.J.F. ter Braak (Biometris, Plant Research International)
for the statistical advice, and J. Burgers, W.K.R.E. van
Wingerden (both Alterra, Wageningen University and
Research Centre) and I.M.G. Vollhardt (Department of
Agroecology, Georg-August University, Go
¨ttingen, Germany)
for their help in the identification of the arthropods. We further
thank D. Kleijn (Nature Conservation and Plant Ecology
Group, Wageningen University and Research Centre) for
providing the laboratory facilities. We gratefully
acknowledge the comments and helpful suggestions from the
anonymous reviewers and the editors.
1.5-1.0
-0.5 0.5
Bem lam
Bem tet
Bem qua
Bem pro
Bem fem
Syn fov Syn tru
Pte ver
Pte str
Not pal
Not big
Cal mel
GFM
HFM
TFM
Axis 1
Axis 2
Fig. 3 Biplot diagram of the redundancy analysis focussing on
the distribution of carabid species in Wageningen-Hoog in
grassy (GFM), herbaceous (HFM) and herbaceous field
margins under a tree line (TFM). Forest is not included
because carabid species were not found in the forest soil.
Species scores are divided by their standard deviations. The
first ordination axis (axis 1) had an eigenvalue of 0.59 and
species–environment correlation of 0.84. The second ordi-
nation axis (axis 2) had an eigenvalue of 0.04 and species–
environment correlation of 0.53. Bem fem =Bembidion
femoratum (Sturm), Bem lam =B. lampros (Herbst), Bem
pro =B. properans (Stephens), Bem tet =B. tetracolum
(Say), Bem qua =B. quadrimaculatum (Linnaeus), Cal
mel =Calathus melanocephalus (Linnaeus), Not big =
Notiophilus biguttatus (Duftschmid), Not pal =N. palustris
(Duftschmid), Syn fov =Syntomus foveayus (Geoffroy), Syn
tru =S. truncatellus (Linnaeus), Pte str =Pterostichus
strenuus (Panzer), Pte ver =P. vernalis (Panzer)
Axis 2
Axis 1 0.10.1-
0.10.1-
Liny
Club Clu
Lyc Tro
Lyc Alo
Lyc Par
Lyc juv
Thom Xys
Tet Pach
Pis Pis
Sal Hel
Gna Zel
HFM
GFM
D
Fig. 4 Biplot diagram of the redundancy analysis focussing on
the distribution of spiders in Achterberg in the ditch (D), grassy
(GFM) and herbaceous field margins (HFM). Species scores
are divided by their standard deviations. The first ordination
axis (axis 1) had an eigenvalue of 0.23 and species–
environment correlation of 0.63. The second ordination axis
(axis 2) had an eigenvalue of 0.10 and species–environment
correlation of 0.67. Club Clu =Clubionidae Clubiona
(Latreille), Gna Zel =Gnaphosidae Zelotes (Gistel), Lyc
Alo =Lycosidae Alopecosa (Simon), Lyc Par =Lycosidae
Pardosa (Koch), Lyc Tro =Lycosidae Trochosa (Koch), Lyc
juv =Lycosidae juvenile, Pis Pis =Pisauridae Pisaura
(Simon), Sal Hel =Salticidae Heliophanus (Koch), Thom
Xys =Thomisidae Xysticus (Koch), Tet Pach =Tetragnathi-
dae Pachygnatha (Sundevall), Liny =Linyphiidae
534 F. Geiger et al.
123
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