1
2
TOPPING
CHRIS
J. TOPPING
and LÖVEI:
and
SPIDERS
GÁBORAND
L. LÖVEI
DISTURBANCE
IN AGROECOSYSTEMS
121
1
Horticulture Research International, Littlehampton, West Sussex BN17 5HL, U.K.
Present address: Department of Landscape Ecology, National Environmental Research Institute, Kalø,
Grenåvej 14, DK-8410 Rønde, Denmark. E-mail:cjt@dmu.dk
2
AgResearch, Flock House Agricultural Centre, Bulls and Horticulture and Food Research Institute,
Private Bag 11030, Palmerston North, New Zealand. E-mail: loveig@hort.cri.nz
2
Author for correspondence.
SPIDER DENSITY AND DIVERSITY IN RELATION TO
DISTURBANCE IN AGROECOSYSTEMS IN NEW ZEALAND,
WITH
A COMPARISON TO ENGLAND
__________________________________________________________________________________________________________________________________
Summary: Spider assemblages were sampled by quantitative sampling in pasture and arable habitats under
different management regimes in the lower North Island of New Zealand. Density and species diversity
increased with decreasing frequency and/or intensity of disturbance from two species and 1.8 individuals m-2
in wheat to 16 species and 130 indiv. m-2 in an abandoned, ungrazed pasture. The spider fauna was dominated
by introduced species of money spiders (Linyphiidae). The most abundant species, Lepthyphantes tenuis, is
also the most abundant one in British cultivated habitats. Additional pitfall trap samples from the same
location and the Waikato, central North Island, indicated a similar species range containing mainly European
species. A sample from a native tussock habitat had a completely different fauna, with only one species
shared with the most undisturbed cultivated area. Comparative samples showed that similarly structured, but
about twice as species-rich assemblages live in similar cultivated habitats in England.
__________________________________________________________________________________________________________________________________
Keywords: spiders, Lyniphiidae, density, diversity, agroecosystems, disturbance, New Zealand, England.
Introduction
Many spiders are preadapted to habitats with large
spatial and temporal variability (Wise, 1993) and
constitute an abundant and widespread group of
polyphagous predators in ephemeral and disturbed
habitats, including cultivated land. In the Northern
Hemisphere, spiders are regarded as significant
natural enemies of arthropod pests (Riechert and
Lockley, 1984; Nyffeler and Benz, 1988; Sunderland
et al., 1986).
Agricultural habitats in New Zealand are
evolutionally recent and bear close resemblance to
similar habitats in the Northern Hemisphere,
especially Europe, both in terms of flora and fauna
(Lövei, 1991). It is likely that spiders play an
important role in these habitats. However,
information on spiders in agricultural fields in New
Zealand is scarce. Martin (1983) listed 47 species
collected in pasture during three years near Nelson,
South Island. Most of the spiders were not identified
to species and general notes on abundance are given
for a few species only. European species of
linyphiids, Eperigone fradeorum (Berland)*,
*Misidentified as Erigone tridentata (A. MacLachlan,
pers. comm., Lincoln University, Lincoln, N.Z.)
E. wiltoni Locket, Leptyphanthes tenuis (Blackwall)
dominated in pitfall trap catches.
In this paper, we provide the first quantitative
data on the density and diversity of spiders in New
Zealand cultivated land under different management
regimes, and compare the species assemblages with
those found in similar habitats in England.
Methods
Quantitative sampling, New Zealand
Our main study site was on the AgResearch farm at
Flock House near Bulls (40o10’S, 175o23’E), in
southern North Island, New Zealand. Spiders were
collected from nine different agricultural habitats
during the southern spring (late November) of 1992.
In each habitat, five sampling units of 1 m2 each
were selected and isolated by a 150 mm tall steel
ring. Spiders were collected by a modified D-vac
suction sampler (30 sec suction) with subsequent
hand-searching (Topping and Sunderland, 1994).
This method provides a good estimate of ‘true’
density data for spiders; D-vac samples that are not
supplemented by hand-searching underestimate
spider density (Topping and Sunderland, 1994).
New Zealand Journal of Ecology (1997) 21(2): 121-128 ©New Zealand Ecological Society
122
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 21, NO. 2, 1997
We selected nine habitats forming a series of
management operations (disturbance) of different
intensity and frequency:
1. Conventionally managed spring wheat paddock
{CW}, in its second consecutive year in wheat.
2. Organically managed spring wheat {OW}, first
year in wheat. This plot had an ‘organic’
certification, conforming to the international
Bio-Gro standards. No artificial fertiliser or
pesticide was applied. Weeds were controlled
mechanically, twice during early spring, when
the wheat plants were not taller than 15 cm.
The previous crop was a ryegrass (Lolium
perenne L.) - white clover (Trifolium repens L.)
pasture.
3-5. Ryegrass - white clover pasture blocks
subjected to rotational sheep grazing at high
(HG; 28 ewes ha-1), medium (MG; 15 ewes
ha-1) and low stocking rates (LG; 5 ewes ha-1).
An area within the paddock was grazed for
about one week every 15 weeks.
6. a ryegrass - white clover pasture ungrazed
for 6 months {NG}, previously under
rotational grazing at medium stocking rates by
sheep.
7. a ryegrass - white clover pasture abandoned for
one year {AP}, previously under rotational
grazing at medium stocking rates by sheep.
Habitats marked 1-7 were 2 - 2.3 ha in size.
8. a roadside grassy verge, subject to mowing once
a year, during the summer {RV}. The dominant
plant species were perennial ryegrass, Poa
annua L., Phleum pratense L., and sparse
flowering weeds (Matricaria sp., Lamium sp.,
A. Maclean and J.M. Hickman, pers. comm.).
9. An experimental plot of species-rich pasture
(0.5 ha), planted with a grass/herb mixture
containing 16 species {HP}. This plot was
planted two years before the sampling, and was
not treated, cut or grazed.
Pitfall trapping, New Zealand
Additionally, spiders were collected by pitfall
trapping from an organically managed, ungrazed
plot of serradella (Ornithopus sativus Brotero) at
Flock House, over seven weeks between 20
December 1990 and 7 February 1991. The serradella
was in its first year, and the plot was free of weeds,
except sparse mayweed (Matricaria sp.) plants
around the edges. Ten pitfall traps were deployed
along a straight line, starting from the edge of the
paddock and running towards the centre. Individual
traps were 10 m from each other. A pitfall trap
consisted of a 0.5 L plastic pot filled with 300 mL of
70% ethylene glycol, and covered by a metal square
‘roof’ to protect the catch from birds, small
mammals and rain. Traps were controlled weekly
and the catch was collected, sieved, and stored in
70% ethanol until identification. The total trapping
effort was 490 trap-days.
Two further series of pitfall trap sampling were
used for comparisons, collected from two pastures
near Hamilton (37o47’S, 175o17’E), in the Waikato
region of the North Island, New Zealand, during
October-December 1990. Site A at Ruakura was
sown in 1980 with perennial ryegrass and white
clover (Trifolium repens L.). At the time of
sampling, it had substantial ingress of P. annua and
was grazed by dairy cows. Trapping effort here was
350 trap-days. Site B, Rukuhia, was sown in 1978
with perennial ryegrass cv. ‘Grasslands Nui’ and
white clover cv. ‘Grasslands Pitau’. By 1990, it also
had ingress of P. annua. This pasture was grazed by
sheep. The trapping effort was 560 trap-days. At
both sites, 10 pitfall traps, with ethylene glycol as
preservative, were deployed.
Quantitative sampling from non-cultivated
habitat, New Zealand
For comparison with the spider assemblage of
cultivated habitats, ten D-Vac suction samples of
1m2 (using the metal ring and hand searching as for
the other quantitative samples) were also taken from
a scarce tussockland habitat, dominated by
Chinochloa rubra on the central Volcanic Plateau of
the North Island near the top of the Desert Road
(850 m a.s.l.; 39o13’S, 175o45’E), in November
1992.
Quantitative sampling, England
Intercontinental comparisons of the assemblage
structure were made with spider assemblages
collected from two fields of winter wheat in Sussex,
southern England (Grid Refs. TQ0403, 50o49’N,
00o31’W, and TQ1807, 50o51’N, 00o19’W, Both
fields were sampled using 15 density samples of
0.5 m2 each in an identical manner to that used for
the New Zealand sampling (Topping and
Sunderland, 1994). These were conventionally
managed winter wheat fields receiving fungicide and
fertiliser but no insecticide applications during the
sample seasons (i.e. none were necessary). Both
fields were in rotation with grass and oil-seed rape.
TQ 1807 was in grass the year before, the other in
wheat. The fields were at 20 m and 70 m a.s.l.,
respectively.
TOPPING and LÖVEI: SPIDERS AND DISTURBANCE IN AGROECOSYSTEMS
123
Table 1: Total spider catch resulting from density sampling of nine agricultural habitats, arranged in decreasing degree of
disturbance, at Flock House, Bulls, New Zealand. CW - conventional wheat; OW - organic wheat; HG, MG, LG, NG grazed paddocks, with high, medium, low and no grazing; RV - roadside verge; AP - abandoned pasture; HP - herb/
pasture. For more details, see Methods.
__________________________________________________________________________________________________________________________________
Species
CW
OW
HG
MG
LG
NG
RV
AP
HP
Total
0
0
4
0
0
3
2
0
0
0
3
4
0
0
0
5
11
0
0
0
76
0
50
0
0
2
11
0
0
0
24
0
41
0
0
37
69
0
0
2
15
0
1
0
0
5
49
0
3
15
1
0
0
0
1
40
403
0
35
98
2
0
0
2
0
37
184
1
4
136
0
0
1
2
0
21
268
0
32
213
129
4
118
4
1
153
998
1
74
464
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
2
0
0
0
0
0
0
0
0
5
1
0
0
0
0
0
0
0
4
3
0
0
1
1
2
8
1
1
30
1
1
0
0
5
3
1
15
34
1
1
1
1
7
11
0
0
0
0
0
0
0
2
2
0
0
0
0
0
0
0
0
0
0
1
0
1
2
1
1
3
3
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
0
0
2
0
0
0
1
2
3
0
0
4
85
11
16
17
107
0
0
0
0
0
0
0
0
0
0
0
0
2
3
0
1
2
4
0
0
0
0
0
0
0
0
2
1
0
0
0
0
0
0
2
1
0
0
0
0
0
0
0
0
0
0
0
2
1
3
0
0
1
5
0
0
1
0
0
0
0
0
1
0
0
0
0
0
2
2
42
46
25
12
13
4
5.0
142
81
61
4
28.4
174
62
112
5
34.8
99
30
69
7
19.8
__________________________________________________________________________________________________________________________________
LINYPHIIDAE
Erigone wiltoni
8
Eperigone fradeorum
0
Erigonine Immatures
21
Diplocephalus cristatus
0
Microtenonyx subitaneus (O.-P. Cambridge) 0
Lepthypantes tenuis
3
L. tenuis immatures
1
Diplocenta spp.
0
Mynoglenes diloris
0
M. diloris immatures
0
THERIDIIDAE
Th1
0
Th2
0
Th2 immature
0
Th3
0
Th4
0
Th5
0
Th5 immature
0
Th7
0
Th7 immature
0
TETRAGNATHIDAE
Tetragnatha spp.
0
ARANEIDAE
Ar1 immatures
0
Ar2 immatures
0
SALTICIDAE
Sa1 immature
0
Sa2
0
LYCOSIDAE
Ly1
0
Ly11 Immatures
0
OXYOPIDAE
Ox1
0
Immatures
0
GNAPHOSIDAE
Anzacia gemmea Dalmas
0
Anzacia spp. immature
0
CLUBIONIDAE
Clubiona clima Forster
0
Immatures
0
CYATHOLIPIDAE
Tekelloides spp.
0
Unknown Family
Un1 immatures
0
Total
Adults
Immatures
Number of species
Density, individuals m-2
33
11
22
2
6.6
9
3
6
2
1.8
599
491
82
60
507
431
8
16
120.0 98.2
651 2213
77
418
574 1795
14
23
130.0
__________________________________________________________________________________________________________________________________
124
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 21, NO. 2, 1997
Pitfall trapping, England
Pitfall trap samples from two perennial ryegrass
pastures, obtained from the northeast of England
(Grid Ref. NZ 1367, 55o00’N, 01o48’W, 100 m
a.s.l.) were compared to pitfall trap catches from
New Zealand.
Pitfall traps consisted of 110 mm deep x 85 mm
diameter polypropylene cups, with undiluted
ethylene glycol as preservative. Lids or covers were
not used on the traps. Traps were placed in a transect
across the sampled area consisting of 12 traps 1 m
apart. The first nine undamaged traps recovered
were used in the analysis.
Both pasture sites were 1 y old perennial
ryegrass swards. Two cuts of silage were taken
during the sample year and the sites were grazed by
cattle afterwards. The samples were taken in late
May which corresponded in season to those taken
in New Zealand. The total trapping effort was 360
trap-days
Evaluation and identification
To describe the diversity of spider assemblages, we
used species richness (S), which is the simplest but
legitimate measure of diversity, and is often as
informative as the more complicated diversity
indices (Southwood, 1978).
All spiders were identified using the available
identification keys (Forster, 1967, 1970, Forster and
Wilton, 1968, 1973; Forster and Blest, 1979;
Roberts, 1987, Forster et al., 1988). The taxonomic
status of many New Zealand spider species is still in
doubt, hence a number of morpho-species
encountered could not be identified and were
allotted code numbers. Nomenclature of the
European species follows Roberts (1987).
Results
Spider assemblages in relation to disturbance
in New Zealand
A total of 23 species of spiders were identified in
the quantitative samples from nine habitats sampled
at Flock House. Among habitats, spider species
richness ranged between two and 16, and the
densities varied between 1.8 and 130 individuals m-2
(Table 1).
There was a general trend towards higher
numbers of individuals and species as disturbance
(defined as the frequency/intensity of agricultural
management and/or grazing) decreased. Very high
disturbance levels of the two cultivated sites resulted
in low spider density and a species-poor assemblage
(two species). The most disturbed habitats were the
pasture and cultivated ones. These had a simple
spider assemblage, comprising the introduced
species L. tenuis, E. wiltoni, Mynoglenes diloris
(Urquhart) and a few incidentals such as Eperigone
fradeorum and Diplocephalus cristatus (Blackwall)
(Tables 1- 3). Only three native species were
regularly recorded in the agricultural samples
Table 2: Spider assemblages on an experimental pasture plot, Bulls, North Island, New Zealand. Each sample consited of
10 pitfall traps.
__________________________________________________________________________________________________________________________________
Species
27 Dec
3 Jan
10 Jan
Date
17 Jan
24 Jan
31 Jan
7 Feb
Total
5
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
2
5
2
2
1
10
13
0
15
5
0
3
10
0
9
6
0
19
8
0
20
6
0
40
4
1
116
52
2
2
2
2
0
9
12
29
1
0
0
1
0
0
0
2
1
0
0
0
0
1
0
2
33
23
15
18
27
36
59
211
__________________________________________________________________________________________________________________________________
LINYPHIIDAE
Erigone wiltoni
Eperigone fradeorum
Diplocephalus cristatus
Ostearius melanopygius
(O-P. Cambridge)
Lepthyphantes tenuis
Mynoglenes diloris
LYCOSIDAE
Ly1
DOLOMEDIDAE
Do1
THERIDIIDAE
Th2
__________________________________________________________________________________________________________________________________
Total
__________________________________________________________________________________________________________________________________
TOPPING and LÖVEI: SPIDERS AND DISTURBANCE IN AGROECOSYSTEMS
125
Table 3: Spider assemblages on pastures in the Waikato region, North Island, New Zealand, according to results of pitfall
trap catches.
__________________________________________________________________________________________________________________________________
Location, species
25 Oct
15 Nov
Date
22 Nov
29 Nov
Total
0
2
2
1
34
1
2
1
0
0
5
2
19
6
4
3
53
9
13
7
2
7
5
43
4
11
4
36
15
97
4 Oct
11 Oct
25 Oct
15 Nov
6 Dec
Total
38
11
0
1
5
3
19
8
0
0
10
3
4
4
0
0
1
0
33
10
0
0
12
6
96
26
1
1
15
11
190
59
1
2
43
23
1
59
4
44
5
14
8
69
6
156
24
342
__________________________________________________________________________________________________________________________________
Ruakura
LINYPHIIDAE
Erigone wiltoni
Eperigone fradeorum
Lepthyphantes tenuis
Mynoglenes diloris
LYCOSIDAE
Ly1
Total
Rukuhia
LINYPHIIDAE
Erigone wiltoni
Eperigone fradeorum
Latesia bellissima
Diplopecta spp.
Lepthyphantes tenuis
Mynoglenes diloris
LYCOSIDAE
Ly1
Total
__________________________________________________________________________________________________________________________________
(M. diloris, Th2 and Ly1). Almost all species
recorded from these habitats were money spiders
(Linyphiidae).
The organically managed wheat field did not
support more spiders than the conventionally
managed one: both had only two species, and the
density ratio was 3.5:1 in favour of the conventional
field (Table 1). For the grazed pastures, the species
richness steadily increased with the decreasing
intensity of grazing (from high intensity grazing to
abandoned pasture). In contrast, the density was
highest in the least grazed habitat, and the mediumgrazed habitat had higher spider population density
than the abandoned one (Table 1). Density but not
species richness was three times greater in the
roadside verge than the least grazed pasture. Spider
density in the other two types of ‘abandoned’
habitats (AP and HP) was similar to that recorded in
the roadside verge habitat. Species richness,
however, was higher (Table 1).
In habitats with reduced disturbance, E. wiltoni
no longer formed a significant part of the
assemblage. In contrast, L. tenuis numbers were
higher. M. diloris did not seem to tolerate grazing: of
all the grazed habitats, only two immatures (and no
adults) were caught in the low-intensity grazed
habitat. The prevalence of this species was
consistently higher in less disturbed habitats.
The trends in abundance estimates of the adult
and immature stages roughly coincided, although
habitats with the highest densities had
disproportionately high numbers of immatures
(Table 1).
Spider fauna sampled by pitfall traps
Flock House, Manawatu
A total of 211 individuals of nine species were
collected (Table 2). Weekly catches ranged between
two and seven species, and 15- 59 individuals.
L. tenuis was the most numerous species in pitfall
trap samples followed by the native M. diloris.
These two species made up 80% of the total catch.
The third-ranking species was an unidentified native
lycosid spider, which was caught, although in small
numbers, on all but one sampling occasion.
Ruakura, Waikato
Five species and 97 individuals were caught over the
five weeks of pitfall trapping. Four of these were
introduced linyphiid spiders. The only native species
was the same lycosid caught at Flock House, also
126
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 21, NO. 2, 1997
constantly present in the captures in small numbers.
On two occasions, all the species on the total list
were present in the weekly catch. The number of
individuals per week ranged between 7 and 56. The
catch was dominated by E. wiltoni and L. tenuis
(Table 3).
Rukuhia, Waikato
Seven species and 312 individuals were collected
over eight weeks. Five of these were introduced
linyphiids, with two natives: M. diloris and the
unknown lycosid (Table 3). All the species were
caught in several weekly or fortnightly catches, and
the number of individuals per week varied between 7
and 78. The most numerous species in the catch was
E. wiltoni, followed by E. fradeorum, L. tenuis, and
M. diloris.
Table 4: Spiders collected by suction sampling in
tussockland habitat on the Volcanic Plateau, North Island.
Altitude: 850 m a.s.l. All species thought to be native.
______________________________________________________________
Species
Number of
individuals
______________________________________________________________
LINYPHIIDAE
Diploplecta communis Millidge
Laetesia trispathulata (Urquhart)
Laetesia amoena Millidge
SYMPHYTOGNATHIDAE
Sy1
THERIDIIDAE
Th2
Th8
Th9
Th10
Th11
Th12
LYCOSIDAE
Ly2
Total
Adults
Immatures
Number of species
Density, individuals m-2
12
4
1
2
14
1
1
1
1
1
1
305
39
266
11
30.5
______________________________________________________________
Spider density in native tussockland
Suction sampling from native New Zealand tussock
grassland yielded 305 individuals comprising ten
species (Table 4), of which only three were
linyphiids. Only the most abundant species (theridiid
Th2; see Table 2), was found in samples taken from
the least disturbed agricultural habitats (AG, RV, AP
and HP).
Intercontinental comparisons
Only partial comparisons were feasible, because of
the lack of comparative material. We compared
spider density estimates in English and New Zealand
wheat fields, and pitfall trap catches in ryegrass
pastures in New Zealand and England.
Samples taken using identical methods in
Britain showed that wheat fields in England
contained more spider species than New Zealand
fields (14 and 15 species vs. two species in New
Zealand), and densities were five times higher
(Table 5). Both faunas were dominated by linyphiid
spiders, and L. tenuis was abundant in both. The
New Zealand assemblage can be considered a
subset of the European fauna.
In ryegrass pastures, the same trends were
observed as for the density sampling: there were
more species and higher numbers in Britain than in
New Zealand (Table 6). Linyphiidae again
dominated in both areas.
Discussion
Although the structure of the spider assemblages in
our study area of agricultural land in New Zealand
was similar to that found in England, both species
richness and density were lower in New Zealand.
The New Zealand samples had approximately half
the number of species expected for comparable
habitats in England. The majority of the spiders in
agricultural habitats in both countries were money
spiders (Linyphiidae). Money spiders are highly
dispersive (Duffey, 1956; Sunderland, 1991). In
contrast, New Zealand native species generally have
an allopatric distribution. M. diloris appears to be an
exception to this and has been observed ballooning
in large numbers (R.R. Forster, pers. comm.). Thus,
its dispersal ability, atypical of New Zealand native
spiders, may explain the high abundance of M.
diloris in agricultural habitats. M. diloris seemed to
prefer a complex vegetational architecture, as the
highest densities were found in the two habitats
which are floristically and structurally the most
complex ones (G.L. Lövei and V.K. Brown,
unpublished).
Possibly the most interesting aspect of New
Zealand agricultural spider assemblages is that the
species appear to occupy very similar habitats to
those found in Europe. L. tenuis is the most
abundant spider, with E. wiltoni, also common,
favouring the shorter, more heavily managed swards.
This is almost identical to the situation in Britain
where L. tenuis is often the most abundant and
ubiquitous spider while short swards or arable land
TOPPING and LÖVEI: SPIDERS AND DISTURBANCE IN AGROECOSYSTEMS
Table 5: Spider assemblages in two fields of winter wheat in
Sussex, England, during spring (May 1990). Samples
obtained by D-Vac suction and subsequent hand-searching
on 7.5m2.
______________________________________________________________
Species
Field A,
17 May
Field B,
21 May
0
1
1
1
4
2
10
1
4
2
5
41
3
2
1
6
4
0
1
0
3
0
5
4
9
1
0
1
1
0
2
3
0
1
1
0
0
1
283
204
79
15
37.7
285
243
42
14
38.0
______________________________________________________________
LINYPHIIDAE
Oedothorax apicatus (Blackwall)
O. fuscus (Blackwall)
O. retusus (Westring)
Tiso vagens (Blackwall)
Dismodicus bifrons (Blackwall)
Pananamops sulcifrons (Wider)
Milleriana inerrans (O.P.-Cambridge)
Erigone atra
E. dentipalpis
E. promiscua
Meioneta rurestris (C.L. Koch)
Lepthyphantes tenuis
Bathyphantes gracilis (Blackwall)
THERIDIIDAE
Theridion pallens Blackwall
TETRAGNATHIDAE
Pachygnata degeeri Sundevall
LYCOSIDAE
Pardosa palustris (L.)
THOMISIDAE
Oxyptila sanctuaria (O.P.-Cambridge)
CLUBIONIDAE
Clubiona reclusa O.P.-Cambridge
C. brevipes Blackwall
Total
Immatures
Adults
Number of species
Density, individuals m-2
______________________________________________________________
are favoured by the Erigone species E. atra
(Blackwall), E. dentipalpis (Wider) and E.
promiscua (O.P.-Cambridge) (Topping, 1991;
Topping and Sunderland, 1992). This suggests that
the ecological niches occupied by these species are
broadly similar between continents. If this is the
case, then the lower spider density and diversity in
New Zealand agroecosystems could be due to
differences in habitat structure and a lower
availability of niches, a lack of available colonists or
lower prey resource. New Zealand pastures are
relatively recent, and were established with
European grasses and forage legumes, on land
formerly in forest. New Zealand pastures are in
appearance similar to those in England. Poor
dispersal power may mitigate against successful
invasion of this new habitat by endemic species,
whilst non-native species may not have had the
opportunity to invade. For similar reasons, suitable
prey may be low in abundance and thus limit the
127
occupation of the agricultural habitats to only the
most efficient competitors. Comparative trophic
studies in agroecosystems in Europe and New
Zealand would be necessary to give support to either
of these hypotheses.
Since most of lowland and mid-altitude areas in
New Zealand were covered with forests until the
arrival of man (Wardle, 1991), tussockland was
chosen as an example of a native habitat most likely
to contain spiders pre-adapted to conditions in
cultivated habitats. Although our sample was very
limited, the structure of the spider community found
in tussock was remarkably different from the
agricultural samples. All species collected from the
tussock grassland site were thought to be endemic to
New Zealand and only one (theridiid Th2) was
shared with the agricultural sites sampled. Thus, the
tussock grassland habitat, although apparently
structurally close to some agricultural habitats,
seems to be sufficiently different to almost totally
exclude species overlap.
This pattern is typical of many other groups of
animals and plants in New Zealand (Kuschel, 1990;
Lövei, 1991) leading to the peculiar situation
whereby the ‘imported’ agricultural habitats with
virtually no evolutionary history in New Zealand are
Table 6: Adult spider assemblages on two ryegrass
pastures from the Tyne Valley, England, obtained by pitfall
trapping.
______________________________________________________________
Species
Field 1
Field 2
______________________________________________________________
LINYPHIIDAE
Oedothorax fuscus
32
Oe. retusus
11
Monocephalus fuscipes (Simon)
1
Gongylideillum vivum (O.P.-Cambridge)
0
Savignya frontata (Blackwall)
0
Areoncus humilis (Blackwall)
0
Milleriana inerrans
8
Erigone dentipalpis
327
E. atra
206
Meioneta rurestris
3
Centromerita bicolor (Blackwall)
0
Bathyphantes gracilis
0
Lepthyphantes tenuis
6
TETRAGNATHIDAE
Pachygnatha degeeri
1
P. clerki Sundevall
2
LYCOSIDAE
Pardosa amentata (Clerck)
1
P. palustris
6
P. pullata (Clerck)
1
CLUBIONIDAE
Clubiona reclusa
0
Total
605
Number of species
13
6
1
6
1
4
3
3
98
143
9
1
7
17
1
0
3
0
4
0
307
16
______________________________________________________________
128
NEW ZEALAND JOURNAL OF ECOLOGY, VOL. 21, NO. 2, 1997
found side-by-side with the native habitats. Since
agroecosystems are largely species-poor and
populated by introduced species, there is great
potential for studying the ecological aspects of
community organisation in a simplified natural
environment. With fewer species, niches may be
more easily defined and inter-species interactions
may be less complex and more easily investigated.
Acknowledgements
We would like to thank G. Barker for the use of his
pitfall trap samples, D.J. Hodgson and K.D.
Sunderland for their help with density sampling in
New Zealand, and Britain, respectively, R.R.
Forster, J.M. Hickman, A. Maclachlan, A. Macleod,
W. Stiefel, C. Vink for information, and two
anonymous reviewers for comments on the
manuscript. CJT was supported by a fellowship
under the OECD Project on Biological Resource
Management and a travel grant from the British
Council (Higher Education Link 00984). GLL would
like to thank N.D. Barlow for taking over the
editorial responsibilities for this manuscript.
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