Faunal turnover of arthropod assemblages along a wide gradient of
disturbance in Gabon
Y. Basset1*, O. Missa2, A. Alonso3, S.E. Miller4, G. Curletti5, M. De Meyer6, C.D. Eardley7,
M.W. Mansell8, V. Novotny9 & T. Wagner10
1Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama City, Republic of Panama
2Department of Biology, University of York, P.O. Box 373, York YO10 5YW, U.K.
3Smithsonian Institution/Monitoring and Assessment of Biodiversity Program, 1100 Jefferson Drive, S.W. Suite 3123,
Washington DC 20560-0705, U.S.A.
4Department of Systematic Biology, National Museum of Natural History, Smithsonian Institution, Washington D.C.
20560-0105, U.S.A.
5Museo Civico di Storia Naturale, Cas. Post. 89, 10022 Carmagnola TO, Italy
6Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
7Plant Protection Research Institute, Private Bag X134, Queenswood, Pretoria, 0121 South Africa
8Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002 South Africa
9Biology Center of the Czech Academy of Sciences and School of Biological Sciences, University of South Bohemia,
Branisovska 31, 370 05 Ceske Budejovice, Czech Republic
10Universit?t Koblenz-Landau, Institut f?r Integrierte Naturwissenschaften ? Biologie, Universit?tsstr. 1,
56070 Koblenz, Germany
We examined the results of a study in Gamba, Gabon, focusing on the impacts of disturbance
on arthropods, including more than 400 000 individuals, from which 21 focal taxa were sepa-
rated into 1534 morphospecies by parataxonomists. Replication included the understorey of
three sites in each of four different stages of forest succession and land use (= ?habitats?) after
logging (old and young forests, savanna and gardens), surveyed over a whole year with
three sampling methods. Generally, there was a good correspondence between the number
of species sorted by taxonomists and the number of morphospecies sorted by para-
taxonomists. Despite higher taxonomic groups being present in most habitats, a large
proportion of insect species was site- or habitat-specific. Anthropogenic modification of
habitats did not result in a monotonic decline of abundance and diversity, as many herbivore
pests and their associated predators and parasitoids invaded gardens, where plant produc-
tivity was kept artificially high year-round through watering and crop rotation. Because
gardens were colonized mostly by invasive crop pests with little relation with the forest
fauna, these results emphasize the concept of maintenance of ?quality biodiversity? and
the value of considering other variables than species richness alone in conservation studies.
Further, several lines of evidence indicated that savanna habitats at Gamba supported a
species-poor arthropod fauna distinct from that in nearby habitats. It is therefore question-
able whether in Africa insect assemblages of savanna represent a smaller subset of their
neighboring forest fauna.
Key words: biodiversity; parataxonomy; rainforest; savanna; species replacement, insect
conservation.
INTRODUCTION
The distribution of plant and animal species is a
major theme in ecology. Sadly, evaluating loss of
species following anthropogenic disturbance is
rapidly becoming another significant theme in
ecology and one of the main research topics in
conservation biology. The demise of tropical rain-
forests and the pace at which biodiversity is
inventoried within these forests, especially arthro-
pods, means that many organisms may go extinct
before they are known to science (Wilson 2000).
Whereas the magnitude of this process may be
debatable, what is certain is that we know little of
the majority of species? interactions within tropical
rainforests and therefore how vulnerable they
African Entomology 16(1): 47?59 (2008)
*To whom correspondence should be addressed.
E-mail: bassety@si.edu
may be to anthropogenic disturbance, how quickly
they will be lost and what can be attempted to slow
down these extinctions (Lawton & May 1995).
Reliable data on the vulnerability of species to
extinction and their extinction threats also require
sound biological monitoring of tropical ecosystems,
which is not limited to a few flagship or umbrella
species (Lawton et al. 1998). Thus, a crucial problem
is the consideration of multi-taxa assemblages,
including functional guilds, to properly assess
arthropod responses to disturbance (Didham et al.
1998; Lawton et al. 1998; Kotze & Samways 1999).
Perhaps 80?90 % of tropical taxa have never been
the focus of tropical conservation studies, and the
consequences of this taxonomic selectivity urgently
need to be assessed (Lewis & Basset 2007). Studies
of tropical arthropods and disturbance rarely
provided enough replication for a wide range of
taxa, because of the huge scale of biological effort
involved (Lawton et al. 1998). The task of monitoring
a sufficient number of taxa at various locations with
adequate time may appear daunting. In practice,
training and working with parataxonomists (i.e.
local assistants trained by professional biologists:
Janzen 1992) can help to alleviate these problems
and ensure that statistical replicates are represen-
tative of the system studied (Basset et al. 2004a).
In Africa, basic ecological information on described
species of tropical arthropods is typically fragmen-
tary and often relates to a few locality types.
Largely as a result of Africa?s colonial history, the
insect fauna is probably better known than other
tropical regions, but the information is stored in
European museums and libraries and therefore
often more difficult to locate (Miller & Rogo 2001).
Gaps in our knowledge are evident, even for
well-studied taxa (Miller & Rogo 2001). Further,
studies focused on the impact of anthropogenic
disturbance on arthropods (overview in Miller &
Rogo 2001) are relatively few and often examine a
handful of taxa, usually ants, dung beetles, butter-
flies, termites or mosquitoes (e.g. Nummelin &
Hanski 1989; Eggleton et al. 1995; Watt et al. 1997;
Wagner 2000; Zilihona & Nummelin 2001; Schulz
& Wagner 2002; Stork et al. 2003; Minakawa et al.
2005; Bobo et al. 2006; Lachat et al. 2006). To the best
of our knowledge, with perhaps the exception
of Lawton et al. (1998), there has been no study
(a) dedicated to studying a wide anthropogenic
gradient of disturbance (as opposed to studying
non-disturbed vs disturbed forests), and (b)
selecting a wide range of focal taxa that represent
diverse taxonomic and functional guilds.
Further, although many studies adequately sum-
marize their findings (i.e. by detailing different
variables accounting for community characteristics
and/or providing multivariate analyses displaying
most of the variance of the study system), they
often fail to discuss whether species may be re-
placed along disturbance gradients. Species re-
placement represents an important variable in
conservation studies, which can only be discussed
adequately with identified species (Summerville
2004). Species replacement may be evaluated
statistically by testing whether species may be
considered as site- or habitat-specific. This point is
important if, for example, one wants to discuss the
origin of arthropod assemblages associated with
savanna in Africa (Fisher & Robertson 2002). There
is currently a debate whether rainforest loss in
Africa (and subsequent invasion of savanna) has
been historically triggered by changes in climate
or prehistoric human impacts (Brncic et al. 2007).
Here we examine the results of a study based on
the work of trained parataxonomists in Gabon
(Basset et al. 2004b). Replication included three
sites in each of four different stages of forest
succession and land use (= ?habitats?) after logging,
surveyed over a whole year using three sampling
methods. We evaluated the impacts of disturbance
on a range of arthropod assemblages representing
different feeding guilds. Our specific questions in
this contribution are explicitly focused on taxonomy,
as opposed to analyzing community characteris-
tics (Basset et al. 2004b; 2008), and include whether
 pre-sorting of the material by parataxonomists is
reasonable compared to sorting by taxonomists;
 which higher arthropod taxa are most affected
by habitat changes, in terms of abundance; and
 which morphospecies/species may be considered
as site or habitat-specific in our study system.
MATERIAL AND METHODS
Study area and sites
The study area was in the Shell Gabon oil conces-
sion of Gamba (Table 1), within the Gamba Complex
of Protected Areas in South-East Gabon (see
Alonso et al. 2006 for background and botanical
information). The Gamba oil field includes a mosaic
of old growth secondary rainforests, younger
secondary rainforests and savanna areas, result-
ing mainly from anthropogenic action. Primary
rainforests are absent from the Gamba oil field
48 African Entomology Vol. 16, No. 1, 2008
Basset et al.: Tropical arthropods and disturbance 49
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following the selective logging of Okoum?
(Aucoumea klaineana Pierre). The mean annual
temperature in the area is 26 ?C and annual rainfall
amounts to 2093 mm per year, with the major dry
season from June to August (Alonso et al. 2006).
The Gamba oil field has been active since 1967 and
Gamba has grown from a small village in 1960 to a
town of 8000 inhabitants. The earliest cultivated
crop gardens of notable size were established near
the town in 1998.
We considered four distinct habitats of increas-
ing anthropogenic disturbance (i.e. increasing
forest clearing and introduction of exotic vegeta-
tion) and selected three sites (replicates) within
each habitat. The four habitat types were: (a) ?old
forests?, the understorey of the interior of old
secondary rainforests; (b) ?young forests?, the
understorey of the edge of young secondary rain-
forests; (c) ?savanna?, an area of rainforest cleared
to install oil rigs and subsequently invaded by
savanna; and (d) ?gardens?, cultivated crop gardens.
At the time of the study, there were no substantial
plantations in the area and these four habitat types
were predominant in the Gamba oil field. Salient
characteristics of the study sites (coded A to L) are
indicated in Table 1 (see also Basset et al. 2004b).
Arthropod collecting and processing
Each site was equipped with an identical set of
traps recommended for biological monitoring of
the flying and epigaeic arthropods of the under-
storey and litter: one ground Malaise trap, four
ground yellow pan traps and five pitfall traps
buried in the ground. At each site, a Malaise trap
occupied the center of the set of traps, with four
pitfall traps established to the North, South, East
and West, 10 m distant from the Malaise trap. Four
yellow-pan traps were set up at equal distances
between the pitfall traps, again 10 m distant from
the Malaise trap. The fifth pitfall trap was estab-
lished 30 m north of the Malaise trap. Other details
about the traps and mode of action are given by
Basset et al. (2004b). The 120 traps were operated
for three days during each of the 38 survey periods
from July 2001 to July 2002. A team of eight
parataxonomists was trained and supervised by a
professional entomologist throughout the project;
see Basset et al. (2004a) for detailed discussion of
this strategy and Krell (2004) for critical consider-
ations.
The material collected was first sorted into
families or higher taxa by the parataxonomists.
The material belonging to 21 focal taxa (Table 2)
was separated and pinned, and each individual
was identified by a unique specimen number. The
focal taxa were sorted to morphospecies (i.e.
unnamed species diagnosed using standard taxo-
nomic techniques, sensu Cranston 1990) by the
parataxonomists. Formal taxonomic study of this
material is ongoing but sub-samples of the material
belonging to seven taxa have been examined by
taxonomists (Table 3). The rationale for selecting
the focal taxa were (a) being well represented
in the samples (so that much information was
retained); (b) reasonably well-known taxonomi-
cally; (c) taxonomists having expressed interests in
working on the material; and (d) representation of
a variety of functional guilds and orders (Table 2).
Specimens were stored at the Smithsonian Bio-
diversity Conservation Center in Gamba, and
vouchers have been deposited at the National
Museum of Natural History (Washington D.C.)
and with taxonomists who helped with species
identification.
Statistical methods
As far as possible, we considered data sets of
highest possible taxonomic resolution, including a
mixture of morphospecies and species (see results
concerning the relationships between these two
variables; hereafter referred to as ?species? for sake
of simplicity). To gauge how sorting of insect
material by parataxonomists affected our interpre-
tation of the results and, particularly, the ranking
of sites along the disturbance gradient, we per-
formed a two step analysis. First, we chose a
straightforward approach by quantifying faunal
turnover among sites (beta-diversity) using
detrended correspondence analysis (DCA), with
options set as scaling with Hill?s scaling, detren-
ding the data by segments, and using untrans-
formed data (ter Braak & Smilauer 1998). The
differences between the scores of any two sites on
the first axis of the DCA represent a measure of
species turnover between these two sites. For this
analysis, we considered the larger dataset, includ-
ing the abundance of the most common species
and morphospecies at the different sites (?12 indi-
viduals; i.e. at least on average one individual
collected at each site; 227 morphospecies). Results
of this analysis are detailed and discussed in Basset
et al. (2008). Second, we compared the scores of
sites on Axis 1 of this DCA with similar scores
originating from two similar analyses: (a) a DCA
50 African Entomology Vol. 16, No. 1, 2008
comparing the most common species sorted by
taxonomists and (b) a DCA comparing the most
common morphotaxa as sorted by parataxono-
mists.
Overall abundance and observed species rich-
ness were extracted from raw data for each focal
taxon at each site, since sampling effort was similar
at each site (although not in terms of individuals
collected, species rarefaction detailed in Basset
et al. 2008). We pooled data of the three sampling
methods at a site (data from ten traps) for the 38
surveys and considered this to be a sample
(n = 12). Next, we tested whether arthropod abun-
dance for higher taxa varied significantly across
habitat types with one-way ANOVA and Tukey?s
tests, after log(x + 1) transforming data to satisfy
assumptions of normality (Kolmogorov-Smirnov-
Lilliefors tests, P > 0.05). We used the false discov-
ery rate method to correct for multiple tests. This
procedure calculates the expected proportion of
false positives among all significant hypotheses
with P < 0.05 (Garc?a 2004).
To evaluate which species may be indicative of
particular sites and habitats, we used the indicator
value index (Dufr?ne & Legendre 1997). The indi-
cator values range from zero (no indication) to 100
(perfect indication). Perfect indication means that
the presence of a taxon points to a particular site or
habitat without error, at least with the data set
in hand. We restricted the data set to the most
Basset et al.: Tropical arthropods and disturbance 51
Table 2.Focal taxa considered in this study.Guild assignment follows the system of Moran & Southwood (1982). Ind =
no. individuals collected; Indm = no. individuals morphotyped by parataxonomists (some damaged or lost material
could not be morphotyped;some material collected by flight-interception traps was not considered in this study);Mor =
total no. of morphospecies sorted by parataxonomists from Indm.
Focal taxa Order Guild Ind Indm Mor
Mantodea Mantodea Predators 98 50 19
Acrididoidea1 Orthoptera Leaf-chewers 1129 360 40
Fulgoroidea2 Hemiptera Sap-suckers 4022 2345 233
Membracidae Hemiptera Sap-suckers 37 35 14
Buprestidae Coleoptera Wood-eaters 115 91 14
Scarabaeidae Coleoptera Leaf-chewers, scavengers 2240 1980 81
Coccinellidae Coleoptera Predators 1409 1200 32
Histeridae Coleoptera Predators 682 589 20
Cleridae Coleoptera Predators 45 18 12
Tenebrionidae Coleoptera Scavengers 839 605 54
Cerambycidae Coleoptera Wood-eaters 278 79 34
Chrysomelidae Coleoptera Leaf-chewers 2285 1,761 157
Neuroptera3 Neuroptera Predators 235 133 21
Asilidae Diptera Predators 409 333 47
Dolichopodidae4 Diptera Predators 7339 2113 38
Tephritidae Diptera Leaf-chewers5 535 426 34
Syrphidae Diptera Predators, scavengers 459 369 32
Pipunculidae Diptera Parasitoids 123 97 16
Ichneumonidae Hymenoptera Parasitoids 2302 1880 420
Chalcidoidea6 Hymenoptera Parasitoids 4577 1302 175
Apoidea7 Hymenoptera Leaf-chewers8 1239 1049 93
1Including Acrididae (Acr), Pyrgomorphidae (Pyr), and many juveniles, not morphotyped.
2Including Achilidae (Ach), Cixiidae (Cix), Delphacidae (Del), Derbidae (Der), Dictyopharidae (Dic), Eurybrachidae (Eub), Flatidae (Fla),
Fulgoridae (Ful), Issidae (Iss), Meenoplidae (Mee), Ricaniidae (Ric), Tettigometridae (Tem) and Tropiduchidae (Tro).
3Including Berothidae (Ber), Coniopterygidae (Con), Chrysopidae (Chy), Dilaridae (Dil), Hemerobiidae (Hem), Mantispidae (Mat),
Myrmeleontidae (Mym) and Osmylidae (Osm).
4Only morphotyped from July?December 2001, then kept unassigned in alcohol.
5Subguild: fruit-feeders.
6Only >2 mm and including Agaonidae (Aga), Chalcididae (Cha), Elasmidae (Ela), Encyrtidae (Enc), Eucharitidae (Euc), Eulophidae (Eul),
Eupelmidae (Eup), Eurytomidae (Eur), Leucospidae (Leu), Perilampidae (Per), Pteromalidae (Pte), Tetracampidae (Tet) and Torymidae
(Tor).
7Including Apidae (Api), Halictidae (Hal) and Megachilidae (Meg).
8Subguild: pollinators.
abundant morphospecies (?12 individuals;
n = 227) and tested whether morphospecies were
indicative of particular sites (?site-specific? species),
or of particular habitats (?habitat-specific? species),
particularly for old and young forests (133
morphospecies). The significance of the highest
indicator value for a given species across groups
was tested for each species by Monte Carlo ran-
domization with 1000 permutations, performed
with PC-ORD (McCune & Medford 1999).
RESULTS
In total, 400 404 arthropods were collected by all
collecting methods during the 38 sampling events,
representing 31 orders and at least 218 families.
The 21 focal taxa represented 16 855 individuals
and 1534 morphospecies (Table 2). Further, 347
species were recognized from the seven focal taxa
which to date have been examined by taxonomists
(Table 3). On average, the parataxonomist team
sorted 11 300 specimens for each survey. This
represents a sorting rate of approximately 100
specimens sorted to family and order level per
hour and per person. Most of the material exam-
ined by taxonomists could be assigned between
75?100 % to genera, and between 29?50 % to
known species (Table 3). Generally, there was a
significant and good correspondence between the
number of species sorted by taxonomists and the
number of morphospecies sorted by paratax-
onomists (r = 0.96, P < 0.01, n = 7). However,
parataxonomists often erred on sorting known
species, resulting in between 8 and 44 % of indi-
viduals being wrongly assigned. Most of the errors
involved splitting species into different morpho-
types (Table 3). Bees proved particularly difficult
to sort correctly by parataxonomists. There was a
highly significant correlation between the scores
of sites on Axis 1 of the DCAs performed with
taxonomist data and with parataxonomist data
(r = 0.998, P < 0.001). There were also highly
significant correlations between the scores of sites
on Axis 1 of the DCA based on the larger matrix
(i.e. including all species and morphospecies) and
similar scores from DCAs based on taxonomist
and parataxonomist data (r = 0.986 and r = 0.989,
respectively, P < 0.001).
Community characteristics accounting for the
intensity of faunal changes between habitats
(abundance; observed, rarefied and estimated
species richness; proportion of rare species; diver-
sity partitioning; evenness of assemblages; species
turnover; nestedness; proportion of site-specific
species and ratios of functional guilds) are detailed
elsewhere for each focal taxon (Basset et al. 2004b,
2008). In sum, these analyses indicated that overall
arthropod responses emphasized differences
between forests and open habitats, with cleared
forest subsequently invaded by savanna being the
least populated and less diverse habitat. As far as
species richness was concerned, we could not
consider our disturbance gradient as a series of
impoverished habitats derived from older forests.
When considered at this local scale, anthropogenic
modification of habitats did not result in a
monotonic decline of diversity, as many herbivore
pests and their associated predators and para-
sitoids invaded gardens, where plant productivity
was kept artificially high year-round through
watering and crop rotation. Responses to distur-
bance of most focal taxa were uncorrelated.
Of 55 families representing the focal taxa, 48, 47,
52 African Entomology Vol. 16, No. 1, 2008
Table 3. Target taxa identified by taxonomists. Ide = no. individuals identified by taxonomist; Spp = no. of species
sorted by taxonomist from Ide; Sm = no. of morphospecies sorted by parataxonomists from Ide (% error to no. of
species sorted);Spl = no.spp.split by parataxonomists;Lum = no.spp. lumped by parataxonomists; Indw = no. individ-
uals wrongly assigned by parataxonomists from Ide (% error to total identified); % G = % of generic identifications; %
S = % of species-level identifications; Nov = no. of new species recognized in the material identified.
Target taxa Taxonomist Ide Spp Sm (%) Spl Lum Indw (%) %G %S Nov
Cerambycidae S. Lingafelter 133 51 53 (4) 4 2 10 (8) 75 29 0
Chrysomelidae T. Wagner 899 157 169 (8) 15 3 105 (12) 25 3 3
Galerucini T. Wagner 259 37 49 (32) 15 3 95 (37) 81 11 3
Buprestidae G. Curletti 95 16 16 (0) 2 2 11 (12) 100 50 0
Pipunculidae M. De Meyer 95 22 16 (27) 9 15 32 (34) 100 32 3
Neuroptera M.W. Mansell 106 25 25 (0) 1 1 7 (7) 64 36 0
Apoidea C.D. Eardley 564 51 93 (82) 28 14 249 (44) 100 24 0
42 and 48 families occurred in old forests, young
forests, savanna and gardens, respectively. A few
families of Fulgoroidea were missing in savanna, a
few of Chalcidoidea in forests and savanna and a
few of Neuroptera in all habitats. Family occur-
rence was not significantly different across habi-
tats, as tested with a Kruskal-Wallis test (W =
3.348, P = 0.341). The abundance of 14 of 21 focal
taxa was significantly different among habitats
(Basset et al. 2008). Few taxa were significantly
more abundant in forests than in open habitats
(Cerambycidae, Cleridae and Ichneumonidae).
Many taxa were more abundant in non-forested
habitats and particularly in gardens (Fulgoroidea,
Buprestidae, Coccinellidae, Tenebrionidae,
Neuroptera, Dolichopodidae, Syrphidae,
Pipunculidae, Chalcidoidea and Apoidea). Only
Acridoidea were more abundant in savanna than
in other habitats. As a further illustration of this
trend, Fig. 1 details the abundance per habitat of
the 25 most abundant insect families in our collec-
tions. Among them clear differences emphasized
the better representation of Formicidae, Phoridae,
Cecidomyiidae, Staphylinidae and Gryllidae in
forests, against the clear preferences of Aphidiidae,
Sciaridae, Dolichopodidae and Bethylidae for
gardens. Since, overall, arthropod abundance was
correlated with observed species richness (r =
0.530, P < 0.014, n = 228; data presented in Basset
et al. 2008), we can expect to some extent distribu-
tion patterns of species richness to follow those
reported for abundance.
Most of the species tested could be considered
habitat- or site-specific (92 % and 82 % of species
tested, respectively). Four focal taxa included
species indicative of all habitats, Fulgoroidea,
Scarabaeidae, Dolichopodidae and Asilidae,
(Fig. 2). A high proportion of Apoidea species was
indicative of garden habitats (Appendix 1 online).
When we restricted our comparison between old
and young forests, 29 % of species could be consid-
ered as being significantly habitat-specific, includ-
ing 21 species for old forests and 17 for young
forests. The former category included 10 species of
Basset et al.: Tropical arthropods and disturbance 53
Fig. 1. Mean number of individuals (?1 S.E.) collected per site for the 25 most common insect families, detailed per
habitat (black = old forest, grey = young forest, stippled = savanna, white = garden).Figures indicate the P-value of an
ANOVA with habitat as factor: n.s. = not significant; * = multiple test significant with the false detection rate method
P = 0.003. For sake of clarity: # = all means per habitat scaled by a factor 1/3; $ = all means per habitat scaled by a
factor 1/5; @ = all means per habitat scaled by a factor 1/15.
is: 
# Cicadellidae n.s. 
Aphldiidae 0.0001* 
1 i Aleyrodidae n.s. 
t-j . . . - 
Gryllidae 0.031 
Staphylinidae 0.037 
3__, Scarabaeidae n.s. 
Elatehdae 0.037 
 1 .   Nitidulidae n.s. 
Chrysomelldae n.s. 
Curculionidae n.s. 
i $ Cecidomyiidae 0.042 
Sclahdae 0.011 
Mycetophilidae n.s. 
Chironomidae n.s. 
4 
# Phoridae 0.040 
^z 
H Empiddae 0.032 
-i 1 Drosophilidae n.s. 
34 Bethylldae 0.0001* 
i   Ichneumonidae n.s. 
^ Scelionidae n.s. 
Ddlchopodldae 0.003* 
Formicidae 0.001* 
M        H 
500 1000 1500 2000 
Mean number of individuals collected per site 
2500 3000 
Ichneumonidae, three of Chrysomelidae, two
each of Achilidae and Cixiidae, and one each of
Fulgoridae, Scarabaeidae, Asilidae and Dolicho-
podidae. Significant indicator species for young
forests included four species of Ichneumonidae,
three each of Derbidae and Scarabaeidae, two of
Chrysomelidae, and one each of Cixiidae, Histe-
ridae, Tenebrionidae, Asilidae and Chalcididae.
The most widespread species, as estimated by site
occupancy, included 22 species present in all four
habitats and at least in eight sites: ten species of
Dolichopodidae, four of Scarabaeidae, and one
each of Cixiidae, Histeridae, Chrysomelidae
[Galerudolphia tenuicornis (Jacoby)], Asilidae,
Ichneumonidae, Chalcididae and Apidae (Apis
mellifera L.).
We now briefly discuss species replacement
among habitats for species of focal taxa identified
at least to genus (Appendix 1 online). Beside a
species of Coptops common in gardens, Ceramby-
cidae were only abundant in forests and included
various species of Monochamus, Pseudoxylamia,
Litopus, etc. Apart from two species of Glenea and
Pseudoxylamia, common in both old and young for-
ests, most species were collected in low numbers
in one of the two forest habitats. Our chrysomelid
samples from old and young forests included
many species from a yet undescribed genus near
Barombiella, typical from lowland rainforests of the
Guineo-Congolian forest block. Other species
well-represented in our forest habitats included
Bonesia sp. and Galerudolphia tenuicornis, a species
which has been mainly recorded from forests
through the Congo Basin to Zambia (Bolz &
Wagner 2005). Many chrysomelid species re-
corded from gardens included crop pests, such as
Lema spp. often feeding on Convolvulaceae and
Dioscoreaceae; Diacantha, Lamprocopa, and Leptau-
laca feeding on Cucurbitaceae; Smaragrina feeding
on Polygonaceae and Solanaceae; and some rather
polyphagous species in the genera Luperus and
Exosoma (Jolivet & Hawkswood 1995).
Among Buprestidae, Agrilus spp. mostly recruited
from forest habitats but Chrysobothris dorsata could
be considered as indicator of gardens. Forest habi-
tats often included neuropteran genera such as
Podallea, Ankylopteryx, Oyochrysa and Spilosmylus,
whereas open habitats were more likely to include
Chrysoperla, Italochrysa, Myrmeleon and Nemoleon.
The pipunculid genera, Eudorylas and Tomosvaryella,
were almost exclusively collected from savanna
and gardens. Eudorylas spp. are confirmed parasi-
toids of Cicadellidae (Skevington & Marshall, 1997).
Bees collected in the understorey mostly origi-
nated from savanna and gardens, with genera
such as Allodape, Apis, Braunapis, Lipotriches,
Halictus, Lasiglossum and Patellapis particularly
common in gardens.
54 African Entomology Vol. 16, No. 1, 2008
Fig. 2. Number of habitat-specific species for each focal taxon, detailed per habitat (black = old forest, grey = young
forest, stippled = savanna, white = garden).
ZZ]   Mantodea 
? i 3 Acridoidea 
' i 
Fulgoroidea 
? 
Membracidae 
Buprestidae 
3 Coccinellidae 
] Histeridae 
Clehdae 
3 Tenebrionidae 
Cerambycidae 
Neuroptera 
i     ? ? Asilidae 
3 Tephritidae 
3   Syrphidae 
3 Pipunculidae 
3 ScarabaeWae 
Chrysomelidae 
Dolichopodidae 
Ichneumonidae 
3 Chalcidoidea 
3   Apoidea 
10 20 
Number of habitat-specific species 
30 
DISCUSSION
Limitations of the study
Our project is unusual for a study on the effects
of anthropogenic disturbance on tropical arthro-
pods because (a) it considers a wide gradient of
disturbance beyond the usual disturbed/undis-
turbed forest dichotomy; (b) high spatial and
seasonal replication; (c) use of different sampling
methods; (d) it examines high numbers of individ-
uals, morphospecies or species; and (e) considers a
wide range of arthropod taxa, accounting for a
variety of orders and functional guilds. That said,
three caveats related to methodological constraints
are evident in our study. First, although sampling
methods used in this study were non-destructive
and easily deployed and maintained during a year
at all studied habitats, they were inadequate for
many arthropod taxa (e.g. Lepidoptera are better
collected with light traps, Agrilinae better collected
with yellow sticky traps, etc.). Entomologists have
devised protocols to survey specific taxa with the
aims of maximizing species inventory. However,
most of these rather qualitative protocols are diffi-
cult to implement in the context of biological
monitoring for assessing the effects of ecosystem
changes on arthropods. Thus, one must recall that
protocols developed for biological monitoring,
such as those used in this study, are not adequate
to estimate local or regional species richness.
Second, forest canopies were not sampled, but
most likely support a significant proportion of
species not overlapping with those foraging in the
understorey (Basset et al. 2001). For example, in
central forests of Gabon at La Makand?, about
300 km from our sites, insect herbivores are
2.5 times more speciose in the upper canopy than
in the understorey (Basset et al. 2001). Further,
most species of Agrilus collected both at La
Makand? and Gamba recruit from the under-
storey of old and young forests, not from the
canopy (Curletti 2000, 2003). Agrilus species rich-
ness at La Makand? was estimated to be about four
times higher in the canopy than in the under-
storey (Basset et al. 2001). Thus, overall estimates of
species richness, including canopy habitats, are
most likely higher in forests than in savanna or
gardens. Third, even if the percentage of
site-specific species may appear high (relative to
the number of species tested), we consider these
results as underestimates, as passive traps are more
likely to collect common, rather unspecialized and
mobile species (Gaston & Lawton 1988). In prac-
tice, the fidelity of many insect species for particu-
lar habitats and study sites is probably higher than
our data suggest.
Working with parataxonomists
Most of the field work, processing and pre-
sorting of the material was achieved by a team of
dedicated parataxonomists (Basset et al. 2000,
2004a). As far as we know, this is the first time a
parataxonomist approach has been used on this
scale in Africa for arthropods. The sorting accuracy
of parataxonomists was reasonable, generally
resulting in good correspondence between their
morphospecies assignment and species sorting by
taxonomists. There were notable exceptions (bees)
that could have been improved by taxonomist
feedback. This critical factor for a sound sorting of
insect material by parataxonomists, not taken
into account in Krell?s (2004) critical review of
parataxonomist studies, was difficult to imple-
ment in our study. Most errors in species assign-
ment resulted from ?splitting? (see Krell 2004 for
similar results), which was encouraged in our
context of low taxonomist feedback. Since sub-
samples sent to taxonomists included a high
proportion of ?doubtful? specimens, the para-
taxonomists probably assigned in reality a higher
proportion of specimens correctly than proportions
reported in Table 3. Although parataxonomists
often sorted species with errors of less than 20 % of
total species, it must be noted that overall levels of
synonymy within the taxonomic community are
also close to 20 % (May & Nee 1995). What might
be the consequences of sorting errors for the inter-
pretation of our data? Admittedly, our morpho-
species assignment may preclude a sound discus-
sion of local species richness for particular assem-
blages. However, since we checked that the
ranking of sites along our obvious gradient of
disturbance was not affected by either paratax-
onomists? or taxonomists? assignments, we con-
clude that this factor is unlikely to greatly modify
the interpretation of our results. In summary, we
agree with Krell (2004) that the work of paratax-
onomists in general has been a great benefit for
biodiversity studies, but that it only represents the
first step in sorting and identifying biological
samples.
Overall differences among habitats studied
In Africa and elsewhere in the tropics, large
arthropod surveys along anthropogenic gradients
Basset et al.: Tropical arthropods and disturbance 55
of disturbance typically examined distribution
patterns for less than 10 000 individuals represent-
ing fewer than 500 species, often belonging to one
of a few taxa (Nummelin & Hanski 1989; Zilihona
& Nummelin 2001; Stork et al. 2003; Bobo et al.
2006; Lachat et al. 2006). Studies performed with
pyrethrum knockdown (Watt et al. 1997; Wagner
2000; Schulz & Wagner 2002) or targeting social
insects or the minute soil fauna (Critchley et al.
1979; Eggleton et al. 1995; Noti et al. 1996) usually
collected larger sample sizes but remained restric-
ted to a few taxa. The pioneering multi-taxa study
of Lawton et al. (1998) with a relatively large sam-
ple size remains unrivaled to date and, therefore,
the generality of its conclusions are difficult to
assess.
Overall differences, considering all focal taxa,
among our habitats were clear. Plant productivity
in gardens was kept artificially high year-round
through watering and crop rotation. This resulted
in higher insect abundance and observed species
richness (Basset et al. 2008). Most arthropod vari-
ables emphasized large differences between
forests and non-forests habitats. Despite higher
taxonomic groups being present in most habitats
and study sites, a large proportion of insect species
was site- or habitat-specific. For example, in
gardens, herbivores were not recruited from the
pool of generalist herbivores in forests, but in-
cluded many insect pests feeding on specific
crops. However, despite the presence of several
habitat-specific species, old and young forests
were difficult to distinguish from one another.
In sum, these results are consistent with other
African studies that indicated few differences
between old-growth and degraded forests when
focusing on the observed richness of a variety of
taxa (Lawton et al. 1998; Nummelin & Hanski 1989;
Stork et al. 2003; Lachat et al. 2006). Our data also
agree with a range of studies, detailed below,
examining particular taxa and indicating either a
decrease or increase of abundance in open habi-
tats. Most of these patterns can be easily explained
by the different life-histories and resource bases of
relevant taxa.
Responses of particular focal taxa to
disturbance
Three focal taxa showed obvious preferences for
forests. As wood-eaters, Cerambycidae are tied
with wood resources and their decline in savanna
or in gardens is therefore understandable (Lachat
et al. 2006). Cleridae are often predators of other
wood-eating species, such as Scolytinae, and are
also expected to decline in open habitats. Desicca-
tion seems to be a critical factor limiting the activity
of parasitoids such as Ichneumonidae (Shapiro &
Pickering 2000), which are rarely collected in hot,
dry and sunny habitats (Gauld 1987).
The high abundance and diversity of African
Acridoidea and Coccinellidae in open and disturbed
habitats, and the fewer but distinct and specialized
species belonging to these taxa in forests, is well
documented (Couturier et al. 1984; Chazeau &
Couturier 1985; Magagula & Samways 2001).
Tenebrionidae are often generalist scavengers
feeding on decaying matter of plant origin and
tended to prefer gardens. Dolichopodidae are
known to be particularly abundant in African
savanna and gardens, where they may be preying
on a variety of homopteran herbivores (Couturier
& Duviard 1976). The later may explain, along
with good flying abilities, why some species of
dolichopodid occurred at nearly all study sites.
The high occurrence of Syrphidae and Pipunculidae
in gardens is likewise probably related to the abun-
dance of their homopterous prey (Aphidiidae,
Aleyrodidae, Cicadellidae) in this habitat. There
are at least two explanations to account for the
high abundance and species richness of Apoidea
in non-forested habitats. First, in forests bees tend
to forage at the top of flowering trees, which were
not sampled in this study. Second, many bees,
especially social bees (Apis, Allodape, Liotrigona,
Meliponula), are dependent on flower density and
generalists and therefore are often more dominant
in disturbed, weedy areas with a high diversity of
flowering plants (Liow et al. 2001; Tylianakis et al.
2006).
Other focal taxa showed no obvious preferences
for particular habitats. Fulgoroidea represent a
diverse assemblage of several families of which
Cixiidae, Derbidae and Fulgoridae preferred forests,
and Delphacidae and Meenoplidae gardens.
Dung beetles were more abundant in savanna
than in other habitats, but of similar species rich-
ness in all habitats studied. In particular, few
differences existed between old and young forests,
as recorded by Nummelin & Hanski (1989) in
Uganda. Dung beetle occurrence is mainly related
to the presence of dung resources provided by
mammals (Nummelin & Hanski 1989) and in our
garden sites probably resulted from soil fertiliza-
tion by compost and manure.
56 African Entomology Vol. 16, No. 1, 2008
CONCLUSIONS
Noti et al. (1996) emphasized the faunal continuum
of soil arthropods from forest to savanna sites in
Congo. However, this situation may be different
for epigaeic and airborne arthropods. Several lines
of evidence in this study indicated that savanna
habitats at Gamba support a species-poor arthro-
pod fauna distinct from that in nearby habitats. As
noted for ants in Madagascar, it is therefore ques-
tionable whether insect assemblages of African
savanna represent a smaller subset of their neigh-
boring forest fauna (Fisher & Robertson 2002).
Whether the faunal assemblages in coastal savan-
nas of Gabon, which today are isolated from the
rich and diverse savannas south and north of the
Congolian forest block (Duviard & Pollet 1973), are
different from assemblages in savannas elsewhere
in Africa would equally represent an issue worthy
of investigation.
Since 1998, garden sites at Gamba have been
colonized mostly by invasive crop pests with little
relation to the forest fauna. Garden assemblages at
Gamba emphasize the concepts of maintenance of
?quality biodiversity? (Magagula & Samways
2001). While these assemblages have high local
alpha diversity (Basset et al. 2008) and may be con-
sidered quite habitat-specific at the local or
meso-scale, they consist mostly of pests, vagrant
and generalist species of lower conservation value
which are unlikely to contribute to high spatial
beta-diversity and overall species richness at the
regional scale. Hence, conservation studies assess-
ing the effects of ecosystem change should imper-
atively report additional variables to species
richness, such as abundance or spatial and tempo-
ral partitioning of species turnover (Tylianakis
et al. 2006), for a sound interpretation of results.
ACKNOWLEDGEMENTS
F. Dallmeier, J. Comiskey, M. Lee, J. Mavoungou
and J.B. Mikissa helped to implement the project.
Parataxonomists B. Amvame, N. Koumba, S.
Mboumba Ditona, G. Moussavou, P. Ngoma, J.
Syssou, L. Tchignoumba and E. Tobi collected,
sorted and data-based most of the insect material
with great competence. S.W. Lingafelter, M.
Foldvari and F.C. Thompson helped with
cerambycid, pipunculid and syrphid identifica-
tions. The project was funded by the Smithsonian
Institution, National Zoological Park, Conserva-
tion and Research Center/MAB Program through
grants from the Shell Foundation and Shell
Gabon. This is contribution No. 105 of the Gabon
Biodiversity Program.
REFERENCES
ALONSO, A., LEE, M.E., CAMPBELL, P., PAUWELS,
O.S.G. & DALLMEIER, F. (Eds) 2006. Gamba, Gabon:
Biodiversit? d?une for?t ?quatoriale africaine/Gamba,
Gabon: Biodiversity of an equatorial African rain-
forest. Bulletin of the Biological Society of Washington 12:
1?436.
BASSET, Y., ABERLENC, H-P., BARRIOS, H., CURLETTI,
G., B?RANGER, J-M., VESCO, J-P., CAUSSE, P.,
HAUG, A., HENNION, A-S., LESOBRE, L.,
MARQUES, F. & O?MEARA, R. 2001. Stratification
and diel activity of arthropods in a lowland rainforest
in Gabon. Biological Journal of the Linnean Society 72:
585?607.
BASSET, Y., MAVOUNGOU, J.F., MIKISSA, J.B., MISSA,
O., MILLER, S.E., KITCHING, R.L. & ALONSO, A.
2004. Discriminatory power of different arthropod
data sets for the biological monitoring of anthro-
pogenic disturbance in tropical forests. Biodiversity
and Conservation 13: 709?732.
BASSET, Y., MISSA, O., ALONSO, A., MILLER, S.E.,
CURLETTI, G., DE MEYER, M., EARDLEY, C.,
LEWIS, O.T., MANSELL, M.W., NOVOTNY, V. &
WAGNER, T. 2008. Choice of metrics for studying
arthropod responses to habitat disturbance: one
example from Gabon. Insect Conservation and
Diversity 1: 55?66.
BASSET, Y., NOVOTNY, V., MILLER, S.E. & PYLE, R.
2000. Quantifying biodiversity: experience with
parataxonomists and digital photography in New
Guinea and Guyana. BioScience 50: 899?908.
BASSET, Y., NOVOTNY, V., MILLER, S.E., WEIBLEN,
G.D., MISSA, O. & STEWART, A.J.A. 2004. Conserva-
tion and biological monitoring of tropical forests: the
role of parataxonomists. Journal of Applied Ecology 41:
163?174.
BOBO, K.S. , WALTERT, M., FERMON, H.,
NJOKAGBOR, J. & M?HLENBERG, M. 2006. From
forest to farmland: butterfly diversity and habitat
associations along a gradient of forest conversion in
southwestern Cameroon. Journal of Insect Conserva-
tion 10: 29?42.
BOLZ, H. & WAGNER, T. 2005. Revision of Galerudolphia
Hincks, 1949 (Coleoptera: Chrysomelidae,
Galerucinae). Insect Systematics and Evolution 35:
361?400.
BRNCIC, T.M., WILLIS, K.J., HARRIS D.J. & WASHING-
TON, R. 2007. Culture or climate? The relative influ-
ence of past processes on the composition of the
lowland Congo rainforest. Philosophical Transactions of
the Royal Society of London, Series B. 362: 229?242.
CHAZEAU, J. & COUTURIER, G. 1985. Col?opt?res
Coccinellidae de C?te d?Ivoire: la faune de la for?t de
Basset et al.: Tropical arthropods and disturbance 57
Ta?. Revue Fran?aise d? Entomologie 7: 309?330.
COUTURIER, G., DONKSOFF, M., DUVIARD, D. &
LECORDIER, C. 1984. Influence de la p?n?tration
humaine sur les peuplements entomologiques en
for?t de Ta? (C?te d?Ivoire). II. Les peuplements
Acridiens. Annales de l? Universit? d? Abidjan, s?rie E
(Ecologie) 17: 153?182.
COUTURIER, G. & DUVIARD, D. 1976. Ethologie des
peuplements de Dolichopodidae (Diptera) des sava-
nes vierges et cultiv?es de C?te d?Ivoire Centrale.
Cahiers de l? ORSTOM, s?rie Biologie 11: 97?113.
CRANSTON, P.S. 1990. Biomonitoring and invertebrate
taxonomy. Environmental and Monitoring Assessement
14: 265?273.
CRITCHLEY, B.R., COOK, A.G., CRITCHLEY, U.,
PERFECT, T.J., RUSSEL-SMITH, A. & YEADON, R.
1979. Effects of bush clearing and soil cultivation on
the invertebrate fauna of a forest soil in the humid
tropics. Pedobiologia 19: 425?438.
CURLETTI, G. 2000. Gli Agrilus della spedizione ?Radeau
des cimes? ? Gabon 1999 (Coleoptera, Buprestidae).
Lambillionea 100: 459?470.
CURLETTI, G. 2003. Les esp?ces du genre Agrilus (Curtis,
1825) recueillies au Gabon par le programme
d??valuation et de surveillance de la biodiversit? de la
Smithsonian Institution. (Coleoptera, Buprestidae).
Entomologia Africana 8: 14?20.
DIDHAM, R.K., HAMMOND, P.M., LAWTON, J.H.,
EGGLETON, P. & STORK, N.E. 1998. Beetle species
richness responses to tropical forest fragmentation.
Ecological Monographs 68: 295?323.
DUFR?NE, M. & LEGENDRE, P. 1997. Species assem-
blages and indicator species: the need for a flexible
assymetrical approach. Ecological Monographs 67:
345?366.
DUVIARD, D. & POLLET, A. 1973. Spatial and seasonal
distr ibution of Diptera, Homoptera and
Hymenoptera in a moist shrub savanna : ecological
behavior of winged insect populations in the savan-
nas of Ivory Coast I. Oikos 24: 42?57.
EGGLETON, P., BIGNELL, D.E., SANDS, W.A.,
MAWDSLEY, N.A., LAWTON, J.H., WOOD, T.G. &
BIGNELL, N.C. 1995. The diversity, abundance
and biomass of termites under differing levels of
disturbance in the Mbalmayo Forest Reserve, south-
ern Cameroon. Philosophical Transactions of the Royal
Society of London, Series B 351: 51?68.
FISHER, B.L. & ROBERTSON, H.G. 2002. Comparison
and origin of forest and grassland ant assemblages in
the High Plateau of Madagascar (Hymenoptera:
Formicidae). Biotropica 34: 155?167.
GARC?A, L.V. 2004. Escaping the Bonferroni iron claw in
ecological studies. Oikos 105: 657?663.
GASTON, K.J. & LAWTON, J.H. 1988. Patterns in the
distribution and abundance of insect populations.
Nature 331: 709?712.
GAULD, I.D. 1987. Some factors affecting the composi-
tion of tropical ichneumonid faunas. Biological Journal
of the Linnean Society 30: 299?312.
JANZEN, D.H. 1992. A south?north perspective on
science in the management, use, and economic
development of biodiversity. In: Sandlaund, O.T.,
Hindar, K. & Brown, A.H.D. (Eds) Conservation of
Biodiversity for Sustainable Development. 27?52,
Scandinavian University Press, Oslo.
KOTZE, D.J. & SAMWAYS, M.J. 1999. Support for the
multi-taxa approach in biodiversity assessment, as
shown by epigaeic invertebrates in an Afromontane
forest archipelago. Journal of Insect Conservation 3:
125?143.
KRELL, F-T. 2004. Parataxonomy vs. taxonomy in
biodiversity studies ? pitfalls and applicability of
?morphospecies? sorting. Biodiversity and Conservation
13: 795?812.
JOLIVET, P. & HAWKESWOOD, T.J. 1995. Host-Plants of
Chrysomelidae of the World. Backhuys Publishers,
Leiden.
LACHAT, T., ATTIGNON, S., DJEGO, J., GOERGEN, G.,
NAGEL, P., SINSIN, B. & PEVELING, R. 2006. Arthro-
pod diversity in Lama forest reserve (South Benin), a
mosaic of natural, degraded and plantation forests.
Biodiversity and Conservation 15: 3?23.
LAWTON, J.H., BIGNELL, D.E., BOLTON, B.,
BLOEMERS, G.F., EGGLETON, P., HAMMOND,
P.M., HODDA, M., HOLT, R.D., LARSEN, T.B.,
MAWDSLEY, N.A., STORK, N.E., SRIVASTAVA, D.S.
& WATT, A.D. 1998. Biodiversity inventories, indica-
tor taxa and effects of habitat modification in tropical
forest. Nature 391: 72?76.
LAWTON, J.H. & MAY, R.M. 1995. Extinction Rates.
Oxford University Press, Oxford, U.K.
LEWIS, O.T. & BASSET, Y. 2007. Insect conservation in
tropical forests. In: Stewart, A.J.A., New, T.R. & Lewis,
O.T. (Eds) Insect Conservation Biology. 34?56. The Royal
Entomological Society and CABI Publishing,
Wallingford.
LIOW, L.H., SODHI, N.S. & ELMQVIST, T. 2001. Bee
diversity along a disturbance gradient in tropical
lowland forests of south-east Asia. Journal of Applied
Ecology 38: 180?192.
MAGAGULA, C.N. & SAMWAYS, M.J. 2001. Mainte-
nance of ladybeetle diversity across a heterogeneous
African agricultural/savanna land mosaic. Biodiver-
sity and Conservation 10: 209?222.
MAY, R.M. & NEE, S. 1995. The species alias problem.
Nature 378: 447?448.
McCUNE, B. & MEDFORD, M.J. 1999. Multivariate
Analysis of Ecological Data Version 4.10. MjM Software,
Gleneden Beach, Oregon.
MILLER, S.E. & ROGO, L.M. 2001. Challenges and
opportunities in understanding and utilisation of
African insect diversity. Cimbebasia 17: 197?218.
MINAKAWA, N., MUNGA, S., ATIELI, F., MUSHIN-
ZIMANA, E., ZHOU, G., GITHEKO, A.K. & YAN, G.
2005. Spatial distribution of anopheline larval habi-
tats in western Kenyan highlands: effects of land
cover types and topography. American Journal of Tropi-
cal Medicine and Hygiene 73: 157?165.
MORAN, C.V. & SOUTHWOOD, T.R.E. 1982. The guild
composition of arthropod communities in trees. Jour-
nal of Animal Ecology 51: 289?306.
NOTI, M-I., ANDR?, H-M. & DUFR?NE, M. 1996. Soil
oribatid mite communities (Acari: Oribatida) from
high Shaba (Za?re) in relation to vegetation. Applied
Soil and Ecology 5: 81?96.
NUMMELIN, M. & HANSKI, I. 1989. Dung beetles of the
58 African Entomology Vol. 16, No. 1, 2008
Kibale Forest, Uganda: comparison between virgin
and managed forests. Journal of Tropical Ecology 5:
349?352.
SCHULZ, A. & WAGNER, T. 2002. Influence of forest
type and tree species on canopy ants (Hymenoptera:
Formicidae) in Budongo Forest, Uganda. Oecologia
133: 224?232.
SHAPIRO, B.A. & PICKERING, J. 2000. Rainfall and para-
sitic wasp (Hymenoptera: Ichneumonoidea) activity
in successional forest stages at Barro Colorado
Nature Monument, Panama, and La Selva Biological
Station, Costa Rica. Agricultural and Forest Entomology
2: 39?47.
SKEVINGTON, J.H. & MARSHALL, S.A. 1997. First
record of a big-headed fly, Eudorylas alternatus
(Cresson) (Diptera: Pipunculidae), reared from the
subfamily Cicadellinae (Homoptera: Cicadellidae),
with as overview of pipunculid-host associations in
the Nearctic Region. The Canadian Entomologist 129:
387?398.
STORK, N.E., SRIVASTAVA, D.S., WATT, A.D. &
LARSEN, T.B. 2003. Butterfly diversity and silvi-
cultural practice in lowland rainforests of Cameroon.
Biodiversity and Conservation 12: 387?410.
SUMMERVILLE, K.S. 2004. Functional groups and
species replacement: testing for the effects of habitat
loss on moth communities. Journal of the Lepidopterist
Society 58: 114?117.
TER BRAAK, C.J.F. & SMILAUER, P. 1998. CANOCO
reference manual and user?s guide to Canoco for Windows:
Software for Canonical Community Ordination (Version
4). Mirocomputer Power, Ithaca, NY.
TYLIANAKIS, J.M., KLEIN, A-M., LOZADA, T. &
TSCHARNTKE, T. 2006. Spatial scale of observation
affects ?, ? and ? diversity of cavity-nesting bees and
wasps across a tropical land-use gradient. Journal of
Biogeography 33: 1295?1304.
WAGNER, T. 2000. Influence of forest type and tree
species on canopy-dwelling beetles in Budongo
forest, Uganda. Biotropica 32: 502?514.
WATT, A.D., STORK, N.E., McBEATH, C. & LAWSON,
G.L. 1997. Impact of forest management on insect
abundance and damage in a lowland tropical forest
in southern Cameroon. Journal of Applied Ecology 34:
985?998.
WILSON, E.O. 2000. On the future of conservation
biology. Conservation Biology 14: 1?4.
ZILIHONA, I.J.E. & NUMMELIN, M. 2001. Coleopteran
diversity and abundance in different habitats near
Kikhansi waterfalls, in the Udzungwa Mountains,
Tanzania. Biodiversity and Conservation 10: 769?777.
This article is accompanied by supplementary material online at
http://journals.sabinet.co.za/essa
Accepted 21 December 2007
Basset et al.: Tropical arthropods and disturbance 59