Grasshopper (Orthoptera: Acridoidea)
and plant community relationships
in the Argentine pampas
Sandra Torrusio1, Marı́a M. Cigliano2* and Marı́a L. de Wysiecki3 1Facultad de Ciencias

Naturales y Museo, 2Departamento Cientı́fico de Entomologı́a, Museo de Ciencias Naturales,

Paseo del Bosque s/n, 1900 La Plata, Argentina and 3Centro de Estudios Parasitológicos y de

Vectores (Cepave), Calle 2 Nro. 584, 1900 La Plata, Argentina

Abstract

Aim The objectives of this study were to relate species density, richness and relative
abundance of grasshoppers to habitat vegetation and to detect variations in these
variables among native and exotic plant communities which reflected disturbance
history.

Location Twenty-seven sites were selected in 2000 representing a variety of native and
exotic plant communities, with different degrees of disturbance history, in south-east
Buenos Aires province, Argentina.

Methods Grasshopper mean density, species relative abundance and species composi-
tion were estimated at each site via standard flushing and sweep net techniques. Plant
associations at each site were estimated by evaluating the percentage canopy of ground
cover of native perennial grasses, introduced perennial forbs, annual pastures,
halophilous species, perennial pastures, native perennial forbs, introduced annual forbs
and plant species richness. Based on vegetation variables, sites were classified into five
disturbance categories: native grasslands, halophilous grasslands, pastures, moderately
disturbed pastures and highly disturbed pastures.

Results Grasshopper communities from sites dominated by introduced plant species
(forbs, sown grasses and dicots), were characterized by relatively high densities and a
high proportion of potential pest species. Native grassland sites showed lower
grasshopper densities, while halophilous grassland had high densities, but with low
proportion of potential pest species.

Main conclusions Results from this study suggest that the most abundant and
economic important species of the pampas, Dichroplus elongatus, was associated with
sown pasture plants (grasses and dicots) and introduced forbs, and negatively correlated
with natural communities (native vegetation and halophilous species). These relation-
ships imply that appropriate management practices that leave more areas with natural
vegetation and include perennial pastures and native species in the rotations could show
beneficial in reducing the overall density and the proportion of the primary pest species
in south-eastern Buenos Aires province.

Keywords Grasshopper species diversity, plant associations, disturbance, pampas,
community ecology.

*Correspondence: M. M. Cigliano, Departamento Cientı́fico de Entomologı́a, Museo de Ciencias Naturales, Paseo del Bosque S/N, 1900 La Plata, Argentina.

E-mail: cigliano@museo.fcnym.unlp.edu.ar

Journal of Biogeography, 29, 221–229

Ó 2002 Blackwell Science Ltd



INTRODUCTION

Many studies have examined the associations between
grasshopper species and plant community composition.
Plants provide many of the resources required by grass-
hoppers, such as food, appropriate microclimate, and
refuge from predators (Joern, 1979). In grassland ecosys-
tems of North America, there is substantial evidence that
plant community composition determines which grasshop-
per species may occupy a given patch or site (Otte, 1976;
Joern, 1979, 1983; Evans, 1988; Kemp et al., 1990,
2001; Quinn et al., 1991; Kemp, 1992; Fielding &
Brusven, 1993a, 1995; Cigliano et al., 1995; Parajulee
et al., 1997; Schell & Lockwood, 1997; Craig et al.,
1999).

Grasslands are frequently subjected to disturbances and
perturbations that affect resident species. Grazing by verte-
brates can affect communities of both plants (Sala et al.,
1986; Facelli et al., 1988; Sala, 1988) as well as insect
herbivores in general and grasshoppers in particular (Cap-
inera & Sechrist, 1982; Pfadt, 1982; Capinera & Thompson,
1987; Quinn & Walgenbach, 1990; Fielding & Brusven,
1993b; Prendini et al., 1996; Onsager, 2000).

The Pampas, which occupy the Argentine province of
Buenos Aires and parts of the provinces of Entre Rı́os,
Santa Fé, Córdoba, La Pampa and San Luis, originally
supported low density populations of mega herbivores,
while fire, drought and flood may have been the main
forms of natural disturbance (Sala et al., 1986). During the
past 70 years, this region has been the scene of the
development of a vast livestock industry as well as
the centre for a rapid increase of arable farming (Soriano,
1992). Much of the original natural grassland in the
pampas has been replaced by cropland and by arable
pastures, grazing pressure by livestock has led to the
displacement of native grasses by exotic species and dicots
of low forage quality (Sala et al., 1986; Chaneton et al.,
1988; Facelli et al., 1988). Furthermore, in recent years,
increasing number of farmers have abandoned the practice
of including perennial pasture crops in rotations. Introduc-
tion of forage-crop technology from temperate humid
areas, and the lack of appropriate evaluation of natural
resources, have also contributed to a poor understanding of
the value of native grasslands to the farming economy
(Soriano, 1992).

Grasshoppers are the dominant native herbivore through-
out the pampas and occasionally cause extensive damage to
grasslands and crops in the region (Cigliano & Lange, 1998;
Cigliano et al., 2000). Despite the economic importance of
grasshoppers, little work has been conducted on analysing
the relationship between them and plant communities in the
pampas (Sánchez & de Wysiecki, 1993; de Wysiecki et al.,
2000).

The objectives of this study were to relate species density,
richness and relative abundance of grasshoppers to veget-
ation associations and to detect variations in these variables
among native and exotic plant communities which reflected
disturbance history.

MATERIALS AND METHODS

Study area

The study area was located in Benito Juárez county (530,
772 ha), south-east of Buenos Aires province (60°30¢W,
59°15¢W/37°15¢S 38°00¢S) (Fig. 1). Mean temperature is
21 °C in summer and 7 °C in winter. Average annual
precipitation ranges from 700 in the west to 800 mm in the
east. The dominant native vegetation in the region formerly
consisted of perennial grasses (mostly species of Stipa and
Piptochaetium) (Cabrera, 1968). The area is flat and is
principally used for crop production (winter and summer
crops, covering 28% of the area) and livestock production
(pastures and rangelands covering 60%), with the exception
of some hilly portions (8%) where pristine vegetation can
still be found.

Sampling procedures

Twenty-seven sites were selected in 2000, representing a
variety of native and exotic plant communities and different
degrees of disturbance. Ten sites were native communities,
five of them perennial grasslands dominated by Stipa
caudata, S. neesiana, S. papposa, Piptochaetium stipoides,
P. medium, and Paspalum quadrifarium, and five on
halomorphic soils comprising of a short grass steppe,
dominated by a sparse cover of the grass Distichlis spicata
(Soriano et al., 1992). Six sites were pastures with sown
grasses and dicots (annual and perennial, Avena sp., Melil-
otus officinalis, Medicago sativa, Lolium multiflorum,
Thynopyrum ponticum, among others). The remaining
eleven sites were disturbed pastures invaded by introduced
weeds (perennial and annual forbs) and grazed by livestock.

Vegetation sampling

The vegetation at every site was sampled during January to
coincide with peak standing cover of plants. Five 0.10-m2

(20 · 50 cm) quadrats were sampled along a randomly
selected transect within each site. In each quadrat,

km

Figure 1 Sites used for collection of grasshopper and plant
community data in 2000, Benito Juárez county, Buenos Aires
province, Argentina.

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222 S. Torrusio et al.



percentage canopy cover of each plant species was
estimated in 5% increments following the methods
described by Daunbenmire (1959). Subsequent analysis
were based on pooled mean cover values by plant species
over all quadrats at a point. Plant species that were
unidentifiable in the field were collected and taken to the
laboratory for identification.

Grasshopper sampling

Adult grasshoppers were sampled at each site three times
during the summer (late-December, mid-January and early
February) to maximize chances of detection of species with
different phenological patterns, and to coincide with peak
densities. Community density was estimated by counting the
number of grasshoppers flushed from a series of thirty rings
(0.1 m2), each placed c. 5 m along three transects, following
the method developed by Onsager & Henry (1977). The
relative abundance of each species was determined from 200
net sweeps per site at each sampling period, collected
between 09:30 and 17:00 h under sunny skies and light
winds. Each sweep consisted of traversing an arc of 180°
through the vegetation with a net as described by Evans
(1984, 1988). Grasshoppers collected via sweep net were
placed in plastic bags, put on ice and returned to the
laboratory for identification of species. Density of each
species was calculated by multiplying the proportion of each
species by overall grasshopper density. Averages of the three
grasshopper samples were used for subsequent analyses.

Site classification and vegetation analysis

We tentatively categorized the twenty-seven sites according
to a visual impression of the dominant vegetation, which
reflected disturbance history, as described by Fielding &
Brusven (1993b). Five sites dominated by native grasses were
classified as ‘native grasslands’. Five sites represented by
associations on halomorphic soils were classified as ‘haloph-
ilous grasslands’. Six sites categorized as ‘pastures’ were
dominated by sown pasture plants, both annual and peren-
nial species. The remaining eleven sites were divided into
two categories: ‘moderately disturbed pastures’ (six sites)
and ‘highly disturbed pastures’ (five sites) with different
proportions of introduced, sown and native species of
grasses and forbs. The disturbances included intensive
livestock grazing and the ploughing and sowing of intro-
duced species of grasses and forbs.

Detrended Correspondence Analysis (DCA, the software
MVSP 3.1, 2000) was used for analysis of site classification
into disturbance categories (Hill & Gauche, 1980). Categor-
ies of plant species were considered as variables (e.g.
perennial, annual, natives, introduced) rather than particular
plant species in the analysis. The vegetation variables were:
percentage cover of native perennial grasses, native perennial
forbs, halophilous species, introduced perennial forbs, intro-
duced annual forbs, annual pastures and perennial pastures.

Differences among disturbance categories in percentage
cover of vegetation variables and species richness were

summarized and tested with the non-parametric Kruskall–
Wallis test (SYSTAT 5.02, 1993).

Grasshopper community analysis

Canonical correspondence analysis (CCA – the software
MVSP 3.1, 2000 was employed for this ordination technique)
(ter Braak, 1986, 1987) was used to relate grasshopper
species to the vegetation variables described above. With
CCA, the species ordination axes are constrained to be linear
combinations of specified environmental variables (ter Bra-
ak, 1986, 1987). In our case, the initial vegetation variables
were combined into four groups: native species (native
perennial grasses plus native perennial forbs), halophilous
species, introduced species (introduced perennial plus annual
forbs) and pastures (annual plus perennial grasses). The
results of the CCA ordination were expressed with a biplot
of grasshopper species (Ten grasshopper species found in
four or more sites) and vegetation variables. Species optima
(i.e. the centre of distribution of a species along an
environmental gradient (ter Braak, 1987)), were represented
as points, and vegetation gradients were represented as
arrows extending from the origin of the plot. The length of
each arrow is proportional to the influence that the variable
has on grasshopper species composition (ter Braak, 1986,
1987).

We used Kruskal–Wallis non-parametric one-way analysis
of variance (Siegel & Castellan, 1995; Mendenhall &
Sincich, 1997) to test for differences among the disturbance
categories in grasshopper species richness and total grass-
hopper abundance. Finally, we supplemented and extended
these comparisons using Pearson’s correlation analyses
between the grasshopper and plant variables (e.g. grasshop-
per species richness vs. plant species richness, or Covasacris
albitarsis density vs. percentage cover of halophilous spe-
cies).

RESULTS

Vegetation

The DCA ordination of vegetation variables confirmed the
initial classification by a clear separation among the distur-
bance categories (Fig. 2). The results of the Kruskal–Wallis
tests identified vegetation variables (halophilous species,
introduced perennial forbs, native perennial grasses, peren-
nial pastures) that differed among the disturbance categories
(Table 1). Approximately 72% of the vegetative cover in the
native grassland sites consisted of native perennial species
(52% grasses: Piptochaetium medium, P. ruprechtianum,
P. stipoides, S. neessiana, S. papposa, P. quadrifarium and
20% forbs: Plantago berroi, Eryngium nudicaule, Cliococca
selaginoides). The halophilous associations were dominated
by D. spicata and other halophilous species such as
Hordeum euclaston, Puccinellia glaucescens, Sisyrinchium
sp. and Spergula vilosa. The pastures had high proportion of
sown species (annual and perennial) such as Avena sp. and
different species of Medicago, Melilotus and Lolium. The

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Grasshopper and plant communities in the pampas 223



moderately and highly disturbed pastures were characterized
by different proportions of introduced perennial forbs
(Carduus acanthoides, Taraxacum officinale, Centaurea
solsistialis, Amni majus, etc.), and low percentage of sown
species and native grasses (P. medium, S. formicarum,
S. trichotoma, Bromus brevis). The halophilous associations
and pastures had significantly fewer plant species than the
native grasslands and disturbed pasture sites (Table 1).

Grasshoppers

A total of fifteen grasshopper species (eight Melanoplinae,
three Gomphocerinae, two Acridinae, one Copiocerinae, and
one Leptysminae) were collected at the twenty-seven sample
sites. Five of these species (Dichroplus elongatus, Covasacris
albitarsis, Scotussa lemniscata, D. pratensis and Borellia

bruneri) comprised 87% of the grasshopper assemblage,
while the six least abundant species (Dichroplus conspersus,
Scotussa daguerrei, Baeacris pseudopunctulatus, Sinipta
dalmani, Dichroplus maculipennis and Aleuas lineatus)
together made up 12.3%; four species (Allotruxalis strigata,
Leptysma argentina, Leiotettix pulcher and Scyllinula vari-
abilis) were rare and represented less than 0.7% of the
assemblage. Table 2 lists the fifteen species found with mean
density estimates and feeding habits where known.

Direct gradient analysis by CCA showed relationships of
grasshopper species to the vegetation variables. The CCA
biplot (Fig. 3) indicates, by arrow length, that percentage
cover of halophilous species and native perennial species had
the greatest influence on grasshopper species composition.
The biplot reflects that C. albitarsis and B. bruneri had
optima located in the direction of halophilous species
(halomorphic associations). These two species are grass-
feeders and occupied an average of 11.5 sites. Sinipta
dalmani, S. daguerrei, D. pratensis and B. pseudopunctul-
atus were located in the direction of native perennial species
(native grassland). The first two had a narrower distribution
occupying seven and four sites, respectively, while the
remaining two showed a broader distribution, D. pratensis
being at fourteen sites and B. pseudopunctulatus at nine. The
length of the arrow representing perennial and annual
pastures (sown grasses and dicots) indicates that these
variables were also important in structuring grasshopper
communities. This arrow and the introduced species arrow
are at nearly the same angle, representing pastures and
disturbed sites, respectively. Dichroplus elongatus and
S. lemniscata were located in the quadrant associated with
these variables, indicating a favourable response to sown and
disturbed areas. These species had occupied an average of
sixteen sites. Aleuas lineatus and D. conspersus show no
evident relation with the vegetation variables used in the
CCA analysis.

Results of the Kruskall–Wallis test showed no significant
variation of grasshopper species richness and of total
grasshopper abundance across disturbance categories.
However, grasshopper richness tended to be higher in

Figure 2 Detrended correspondence analysis ordination of study
sites based on five vegetation variables. Sites are indicated by
number. Native grasslands (sites: 5, 19, 22, 25, 30, indicated with
squares), halophilous grasslands (sites: 3, 12, 17, 20, 28, indicated
with triangles), pastures (sites: 1, 2, 6, 9, 14, 15, indicated with
diamonds), moderately disturbed pastures (sites: 7, 10, 11, 13, 16,
21, indicated with circles), highly disturbed pastures (sites: 4, 8, 18,
27, 31, indicated with pentagons).

Table 1 Mean values (ranges) of vegetation variables by disturbance category

Disturbance category

Vegetation variables
Native
grasslands

Halophilous
grasslands Pastures

Moderately disturbed
pastures

Highly disturbed
pastures

% Ground cover
Native perennial grasses* 48 (30–90) 9 (0–20) 1.66 (0–10) 28.3 (10–35) 6 (0–10)
Introduced perennial forbs* 9 (0–25) 3 (0–15) 1.66 (0–5) 24.16 (5–40) 44 (10–75)
Annual pastures 2 (0–10) 2 (0–10) 24.16 (0–100) 20 (0–55) 21 (0–55)
Halophilous species* 0 63 (30–90) 5.83 (0–25) 2.5 (0–15) 0
Perennial pastures* 1 (0–5) 6 (0–20) 61.66 (0–85) 19.16 (0–60) 13 (0–40)
Native perennial forbs 17 (0–35) 2 (0–5) 0.83 (0–5) 1.66 (0–10) 9 (0–35)
Introduced annual forbs 4 (0–10) 0 0 1.66 (0–10) 4 (0–15)
Species richness* 7.2 (3–10) 4.2 (2–7) 4.16 (3–6) 7.16 (6–9) 8.2 (6–11)

*Vegetation variables significantly different among the disturbance category (Kruskal–Wallis tests, P < 0.05).

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224 S. Torrusio et al.



moderately disturbed sites and densities were higher in both
halophilous grasslands and in moderately disturbed pas-
tures (Table 3).

Correlations between grasshopper species and the most
important vegetation variables generally agree with results of
the CCA (Table 4). Some vegetation variables were com-
bined for the correlation analysis. Species positively correla-
ted with percentage cover of halophilous plants (C. albitarsis
and B. bruneri) were located near the halophilous species
arrow. Dichroplus pratensis and S. dalmani were positively
correlated with native plants (native perennial grasses and

forbs) and they were near the native species arrow. Scotussa
lemniscata was positively correlated with sown grasses and
was near this arrow. The remaining grasshoppers species
(D. elongatus, B. pseudopunctulatus, A. lineatus) were not
significantly correlated with any of the variables included in
the study.

Results from correlation analyses between plant species
richness and grasshopper variables (species richness, total
abundance and relative abundance of individual grasshopper
species) are shown in Table 5. Both grasshopper species
richness and total abundance are not significantly correla-
ted with plant species richness. The abundance of both
D. pratensis and D. elongatus increases with plant species
richness, although they prefer different communities, the
former is mostly found on native grasslands and the latter
on moderately disturbed sites. Two grasshopper species
(C. albitarsis and B. bruneri) were negatively correlated with
plant species richness, and occur on halophytic associa-
tions dominated by some grass species. S. dalmani and
B. pseudopunctulatus were positively correlated with plant
richness, and are present on native grassland communities
with a high mean value of plant diversity.

DISCUSSION

Our results yielded broad trends in plant and grasshopper
community patterns in Benito Juarez county. From a
taxonomic perspective, the Melanoplinae was the most
abundant and diverse subfamily, followed by the Gompho-
cerinae, Acridinae, Copiocerinae, and Leptysminae. Similar
patterns were observed at a smaller scale in pastures of La
Pampa province (Sánchez & de Wysiecki, 1993; de Wysiecki
et al., 2000), and at a regional level in the pampas region

Table 2 Mean density, number of sites occupied and food habits of grasshopper species

Subfamily/species Abbreviation *Density Per m2 No. sites occupied Food habits

Melanoplinae
Dichroplus pratensis Bruner Dipr 1.54 14 Mixed-feeders
Dichroplus elongatus Giglio-Tos Diel 3.31 21 Mixed-feeders
Dichroplus conspersus Bruner Dico 0.1 4 n.a**
Dichroplus maculipennis (Blanch.) Dima 0.1 3 Mixed-feeders
Scotussa daguerrei Libermann Scda 0.07 4 n.a**
Scotussa lemniscata (Stal) Scle 1.8 11 n.a**
Baeacris pseudopunctulatus (Ronderos) Baps 0.37 9 n.a**
Leiotettix pulcher (Rehn) Lepu <0.1 2 n.a**
Gomphocerinae
Borellia bruneri Rehn Bobr 1.04 11 Grass-feeders
Sinipta dalmani Stal Sida 0.3 7 Grass-feeders
Scyllinula variabilis (Bruner) Scva <0.1 1 n.a**
Acridinae
Covasacris albitarsis Liebermann Coal 2.35 12 Grass-feeders
Allotruxalis strigata (Bruner) Alst <0.1 1 Grass-feeders
Copiocerinae
Aleuas lineatus Stal Alli 0.47 15 Grass-feeders
Leptysminae
Leptysma argentina Bruner Lear <0.1 1 n.a**

*Mean value, n ¼ 27; **Not available.

– – – –

Figure 3 Canonical correspondence analysis ordination biplot of
the 10 grasshopper species (triangles) (abbreviations listed in
Table 2) occurring at four or more sites and vegetation variables
(arrows) with greatest influence on grasshopper species composition
on Benito Juárez county, Buenos Aires province, Argentina.

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Grasshopper and plant communities in the pampas 225



(Cigliano et al., 2000). However, in the northern range of
the pampas region, at a smaller scale, in Córdoba and Santa
Fé provinces, recent studies showed the Gomphocerinae as
diverse and abundant as the Melanoplinae (Zequı́n et al.,
1999; Beltrame et al., 2001).

The five most abundant species (D. elongatus, C. albitar-
sis, S. lemniscata, D. pratensis and B. bruneri) that
comprised 87% of the grasshopper assemblage, had their
highest densities in different communities. The first ranked
species, D. elongatus, tended to be associated with intro-
duced forbs and sown grasses, dominant in pastures and
disturbed sites. This species, which appears to prefer a mixed
diet of forbs and grasses (Gangwere & Ronderos, 1975), is
very common and widely distributed throughout Argentina,
Chile and Uruguay, considered to be one of the twelve most
important acridid pest species in Argentina (Liebermann,
1972). Dichroplus elongatus can be found almost every-
where in grassland habitats, but it is not common in dry
situations where grass is short or scarce and seems to prefer
low humid habitats, and is also common in cultivated fields
(COPR, 1982). Regional scale grassland surveys reveal that
D. elongatus ranks first in abundance in the pampas
(Cigliano et al., 2000) except in the northern portion of
the pampas region where it lags behind Rhammatocerus
pictus (Zequı́n et al., 1999).

The second most abundant species collected during this
study, C. albitarsis, was closely associated with native
halophilous associations. There are no studies or data
available on the ecology of this species, which has been
recorded for the Argentine provinces of Córdoba, Santa Fé,

Buenos Aires and La Pampa, and for Uruguay. The abun-
dance of B. bruneri was less positively correlated with
percentage coverage of halophilous plant species. This grass-
feeder is found throughout Uruguay, Argentina as far south
as 41°S, and all over Rio Grande do Sul in Brazil (Ronderos,
1968). It is a common grassland species which thrives in
areas of sparse vegetation with patches of bare soil, and is
less abundant where the vegetation is dense and tall
(Carbonell, 1995).

The third-ranked species, S. lemniscata, was positively
correlated with sown grasses and dicots dominant in
pastures and disturbed sites. It is a common grassland
species in Argentina, Uruguay and southern Brazil, and
apparently prefers low, moist places with dense grass
(COPR, 1982).

The fourth-ranked species, D. pratensis, exhibited high
densities in association with native vegetation (grasses and
forbs). This pattern is consistent with published information
on the diet of D. pratensis suggesting it to be a polygphagous
species with a strong preference for forbs (Sánchez & de
Wysiecki, 1990; de Wysiecki & Sánchez, 1992). Dichroplus
pratensis is found throughout Argentina, Uruguay and
southern Brazil, being quite abundant in elevated and
relatively dry grasslands, and is considered to be one of the
twelve species requiring special attention as pests in Argentina
(COPR, 1982). Region-scale grassland surveys showed that
D. pratensis ranks second in abundance, behind D. elongatus
(Cigliano et al., 2000), although, in wide areas of grasslands
in La Pampa province it is the most abundant species (de
Wysiecki & Sánchez, 1993; de Wysiecki et al., 2000).

Table 3 Mean values (ranges) of grasshopper population measures by disturbance category

Disturbance category

Grasshopper
variables

Native grassland
(n ¼ 5)

Halophilous grassland
(n ¼ 5)

Pasture
(n ¼ 6)

Moderately disturbed pastures
(n ¼ 5)

Highly disturbed pasture
(n ¼ 6)

Species richness 4.2 (2–8) 4 (2–7) 4.33 (3–6) 5 (4–7) 3.8 (3–5)
Density (ind. m)2) 8.1 18.98 11.59 12.34 10.72
Individuals/200

sweeps
20 114 44 54 39

Table 4 Results of Pearson’s correlation analysis between densities of individual grasshopper species occupying seven or more sites and
percentage cover of different plant categories

Species
abbreviation

Native vegetation
(grasses and forbs)

Halophilous
species

Sown grasses and dicots
(annual and perennial)

Introduced forbs
(annual and perennial)

Dipr 0.4* )0.21 )0.07 0.007
Diel )0.17 )0.06 0.05 0.13
Scle 0.03 )0.22 0.38* 0.04
Baps )0.04 )0.15 )0.16 0.23
Bobr )0.19 0.63* )0.14 )0.16
Sida 0.63** )0.24 )0.16 )0.01
Coal )0.23 0.95** )0.12 )0.33
Alli )0.03 0.08 0.18 0.06

*P < 0.05, **P < 0.01, n ¼ 27.

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226 S. Torrusio et al.



In our study, grasshopper species richness was not signi-
ficantly correlated with plant species richness. Previous
studies conducted on a diversity of scales also revealed that
grasshopper species richness is probably not a simple
function of the number of plant species. In a study of New
World deserts and arid grasslands, Otte (1976) found that
plant and grasshopper species richness was correlated within
but not between regions. On a smaller scale, among tall grass
prairie sites in Kansas, USA, Evans (1988) reported a positive
correlation between plant and grasshopper species richness
but concluded that the nature of the linkage was not clear.
Fielding & Brusven (1993b) also reported a positive corre-
lation between plant and grasshopper species richness on
Southern Idaho rangeland, USA, but concluded that they
could not identify the underlying processes that generated the
patterns. Recent studies at a landscape level (Kemp et al.,
2001) and at a larger spatial scale along an elevation gradient
(Wachter et al., 1998) in Montana rangeland, USA, did not
yield any clear links between plant and grasshopper species
richness in spite of the observed community level associa-
tions. Similarly, at our study, plant species richness was a
weak predictor of overall grasshopper distribution. Accord-
ing to Kemp et al., 2001) it may be that plant richness is too
coarse a variable to summarize plant community composi-
tion because different sites with similar plant richness values
may have very different plant associations and thus different
ecological resources for the grasshoppers.

Contrary to what was expected, grasshopper species
richness, densities and total abundance did not vary signi-
ficantly among the disturbance categories, although, densi-
ties and total abundance tended to be higher in pastures and
disturbed sites than in native grasslands. Densities were also
comparatively high in halophilous association, mostly be-
cause of the presence of C. albitarsis, which was largely
restricted to this community.

Results from this study suggest that the most abundant
and economic important species of the pampas, D. elong-
atus, was associated with sown plants (grasses and dicots)
and introduced forbs, and negatively correlated with natural
communities (native vegetation and halophilous species).
These relationships imply that appropriate management
practices (for example, Onsager, 2000), that leave more

areas with natural vegetation and include perennial pastures
and native species in the rotations could be beneficial in
reducing the overall density and the proportion of the
primary pest species in south-eastern Buenos Aires province.

We point out, however, that these data were taken during
a year of generally low grasshopper densities (unpublished
data). Long-term monitoring will determine whether these
habitat relationships will change during more favourable
years.

ACKNOWLEDGMENTS

The review and comments of earlier drafts of this manuscript
by W. P. Kemp, J. Lockwood, and anonymous reviewer are
sincerely appreciated. This study was funded in part by a
grant (PIP 653/97) from Consejo Nacional de Investigaci-
ones Cientı́ficas y Técnicas (CONICET), Argentina, and it is
a result of a co-operative programme between the ‘Facultad
de Ciencias Naturales y Museo, UNLP’, the ‘Dirección de
Aplicación de Imágenes Satelitarias, DAIS, Ministerio de
Obras y Servicios Públicos de la Provincia de Buenos Aires’,
and the ‘Municipalidad de Benito Juárez, Provincia de
Buenos Aires’.

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Table 5 Results of Pearson’s correlation analysis between plant
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Grasshopper variables Plant species richness

Species richness 0.23
Total abundance )0.29
Dipra abundance 0.21
Diel abundance 0.17
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BIOSKETCHES

Sandra Torrusio is a PhD student of La Plata National University, Argentina. She has expertise in Remote Sensing and
Geographic Information System Techniques and has worked on several projects from the United Nations Development
Programme (UNDP). Her research interest is the application of GIS and remote sensing to studies on the ecology of grasshopper
communities.

Marı́a Marta Cigliano is Adjunct Professor of Taxonomy in La Plata National University and a Research Scientist from the
National Research Council of Argentina (CONICET). She has conducted research on phylogenetic sytematics, biogeography and
the community ecology of grasshoppers in the United States and Argentina.

Marı́a Laura de Wysiecki is Adjunct Professor at La Plata National University, Argentina. Her research interests include several
topics of grasshopper and locust ecology (Orthopetra: Acridoidea) and the different functional processes of natural grasslands.

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