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Taxonomic and functional composition of arthropod assemblages across contrasting Amazonian forests

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Arthropods represent most of global biodiversity, with the highest diversity found in tropical rainforests. Nevertheless, we have a very incomplete understanding of how tropical arthropod communities are assembled.We conducted a comprehensive mass-sampling of arthropod communities within three major habitat types of lowland Amazonian rainforest, including terra firme clay, white-sand, and seasonally-flooded forests in Peru and French Guiana. We examined how taxonomic and functional composition (at the family level) differed across these habitat types in the two regions.The overall arthropod community composition exhibited strong turnover among habitats and between regions. In particular, seasonally-flooded forest habitats of both regions comprised unique assemblages. Overall, 17.7% (26 of 147) of arthropod families showed significant preferences for a particular habitat type.We present a first reproducible arthropod functional classification among the 147 taxa based on similarity among 21 functional traits describing feeding source, major mouthparts and microhabitats inhabited by each taxon. We identified seven distinct functional groups whose relative abundance contrasted strongly across the three habitats, with sap and leaf feeders showing higher abundances in terra firme clay forest.Our novel arthropod functional classification provides an important complement to link these contrasting patterns of composition to differences in forest functioning across geographic and environmental gradients. This study underlines that both environment and biogeographical processes are responsible for driving arthropod taxonomic composition while environmental filtering is the main driver of the variance in functional composition.This article is protected by copyright. All rights reserved.
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Taxonomic and functional composition of arthropod
assemblages across contrasting Amazonian forests
Greg P. A. Lamarre
1,2,3
*, Bruno H
erault
4
, Paul V. A. Fine
5
, Vincent Vedel
2,3
,
Roland Lupoli
3
, Italo Mesones
5
and Christopher Baraloto
2,6
1
Universit
e Antilles-Guyane, UMR Ecologie des For^
ets de Guyane, 97310 Kourou, French Guiana;
2
INRA, UMR
Ecologie des For^
ets de Guyane, 97310, Kourou, French Guiana;
3
Soci
et
e Entomologique Antilles-Guyane, 97354
R
emire-Montjoly, French Guiana;
4
CIRAD, UMR Ecologie des For^
ets de Guyane, 97310 Kourou, French Guiana;
5
Department of Integrative Biology, University of California, Berkeley, 1005 Valley Life Sciences Building #3140,
Berkeley, CA 94720, USA; and
6
International Center for Tropical Botany, Department of Biological Sciences,
International Center for Tropical Botany, Florida International University, Miami, FL 33199, USA
Summary
1. Arthropods represent most of global biodiversity, with the highest diversity found in tropi-
cal rain forests. Nevertheless, we have a very incomplete understanding of how tropical
arthropod communities are assembled.
2. We conducted a comprehensive mass sampling of arthropod communities within three
major habitat types of lowland Amazonian rain forest, including terra firme clay, white-sand
and seasonally flooded forests in Peru and French Guiana. We examined how taxonomic and
functional composition (at the family level) differed across these habitat types in the two
regions.
3. The overall arthropod community composition exhibited strong turnover among habitats
and between regions. In particular, seasonally flooded forest habitats of both regions com-
prised unique assemblages. Overall, 177% (26 of 147) of arthropod families showed signifi-
cant preferences for a particular habitat type.
4. We present a first reproducible arthropod functional classification among the 147 taxa
based on similarity among 21 functional traits describing feeding source, major mouthparts
and microhabitats inhabited by each taxon. We identified seven distinct functional groups
whose relative abundance contrasted strongly across the three habitats, with sap and leaf
feeders showing higher abundances in terra firme clay forest.
5. Our novel arthropod functional classification provides an important complement to link
these contrasting patterns of composition to differences in forest functioning across geograph-
ical and environmental gradients. This study underlines that both environment and biogeo-
graphical processes are responsible for driving arthropod taxonomic composition while
environmental filtering is the main driver of the variance in functional composition.
Key-words: Amazon, arthropod community, environmental filtering, forest habitat, French
Guiana, functional composition, mass sampling, Peru, trophic cascades
Introduction
Arthropods represent most of the world’s biodiversity,
with the highest species richness totals found in tropical
rain forests. Yet with less than 15 million species
described out of the estimated 6 million insect species
globally (Hamilton et al. 2011; Basset et al. 2012), we
have hardly scratched the surface in our attempt to
quantify arthropod diversity. Moreover, we have little
idea how arthropod communities are structured across
geographical and environmental gradients. In megadiverse
tropical forests, an important component of plant diver-
sity is the turnover of species composition across geo-
graphical regions and contrasting habitats (i.e. beta
diversity, Condit et al. 2002; Tuomisto et al. 2003). Cur-
rent evidence suggests that herbivorous insects may vary
in abundance because of changing environmental condi-
tions across habitat gradients (Novotny et al. 2005;
*Correspondence author. E-mail: greglamarre973@gmail.com
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society
Journal of Animal Ecology 2016, 85, 227–239 doi: 10.1111/1365-2656.12445
Rodriguez-Casta~
neda et al. 2010), or due to geographical
variation in co-evolutionary dynamics (Thompson & Cun-
ningham 2002). However, contrasting predictions have
been made for the contribution of beta diversity to regio-
nal diversity within lowland tropical forests. For instance,
Novotny et al. (2007) present evidence for a greater num-
ber of generalist herbivores resulting in a low species turn-
over across relatively large areas in Papua New Guinea.
In contrast, Dyer et al. (2007) suggest that tropical low-
land forests should have a high arthropod beta diversity
because of higher host specificity than in temperate
forests.
Pioneering attempts to study tropical insect assemblages
involved fogging several individuals of a single tree species
(Erwin 1982). Recently, studies have employed hand col-
lections of known host plant lineages to estimate alpha
and beta diversity and the degree of host specialization
(Novotny et al. 2002, 2006; Ødegaard, Diserud & Ostbye
2005; Dyer et al. 2007; Rodriguez-Casta~
neda et al. 2010;
Basset et al. 2012). While these studies have revealed
important patterns of diversity and specificity of particu-
lar arthropod lineages, they are far from representative of
complete arthropod communities (Ødegaard et al. 2000;
Sobek et al. 2009; Rodriguez-Casta~
neda et al. 2010; De
Vries et al. 2012) or are very restricted in geographical
area (Novotny et al. 2005; Basset et al. 2012). A more
comprehensive macroecological approach would sample
entire arthropod communities at large geographical scales
using a combination of traps in a wide variety of habitat
types. Yet to our knowledge, no such community-level
arthropod composition study has been conducted in tropi-
cal rain forests, and therefore, the factors governing
assembly rules in tropical arthropod communities are still
poorly understood.
In the Amazon basin, three broad types of lowland for-
est habitats have been distinguished based on soil texture
and fertility and seasonal water stress, and associated for-
est structure (Baraloto et al. 2011): (i) nutrient-poor and
dry soils of the white-sand forest (hereafter WS) that are
often surrounded by (ii) terra firme clay forest with high
soil nutrient content (TF); and, in low-lying areas nears
rivers and streams (iii) seasonally flooded forests (SF) in
which episodic flooding often submerges soil surfaces dur-
ing periods of high precipitation or Andean snowmelt
(Baraloto et al. 2007). A unique floristic composition
among these three habitats has been detected, with a high
spatial turnover among tree species (Baraloto et al. 2007;
Fine et al. 2010; Wittmann, Sch
ongart & Junk 2010),
including host plant species on which arthropods rely for
nourishment and shelter (Price 2002). A recent study con-
ducted among habitat-specialist tree species has shown
contrasting patterns in leaf production and insect her-
bivory rates across habitats (Lamarre et al. 2014), with
consistently higher rates of leaf production in seasonally
flooded forests (Lamarre et al. 2012a). Contrasting
environmental conditions may therefore select for differ-
ent ecological strategies in tropical trees, including
evolutionary trade-offs in allocation to growth and
defence against herbivores (Fine, Mesones & Coley 2004;
Fine et al. 2006). We therefore predict that arthropod
community composition varies strongly among habitats
types because of differences in resource availability, plant
composition and habitat structure.
Complementary insights into the role of environmental
filtering in community assembly can be gleaned using anal-
yses of functional composition (Cadotte, Carscadden &
Mirotchnick 2011). Most studies examining insect diversity
have focused on species richness or taxonomic composition
(Erwin 1982; Novotny et al. 2002, 2007; May 2010; Basset
et al. 2012). Yet the literature on assembly rules in plant
communities has underlined contrasts between patterns of
taxonomic and functional diversity and composition (Bar-
aloto et al. 2012; Lavorel et al. 2013). It is not uncommon
for unrelated taxonomic groups of arthropods to share
similar functions, such as the leaf-chewing habit of Nym-
phalidae larvae (Lepidoptera) and Chrysomelidae (Coleop-
tera). If food substrates vary across forest types, as
suggested by studies showing denser leaf, stem and roots
tissues in white-sand forests (Fortunel et al. 2014), then we
would predict higher turnover in arthropod functional
composition than might be expected from patterns of turn-
over in taxonomic composition. Turnover in functional
composition may also provide a more meaningful assay of
the role of arthropod communities in ecosystem processes
such as decomposition (Lavorel et al. 2013). In this study,
we sampled representative arthropod communities across
white-sand, terra firme and flooded forests in lowland
Amazonian rain forests of Peru and French Guiana. We
then used these collections to investigate how taxonomic
and functional composition varied across the three con-
trasted tropical forest habitats at broad geographical
scales.
Materials and methods
study sites and environment
This study was conducted in 12 plots within four representative
sites (Fig. 1) that represent the entire range of variation in cli-
matic, edaphic and forest structure factors observed in a larger
plot network in lowland tropical forests of South America in
Loreto, Peru, and French Guiana (Baraloto et al. 2011). Each
plot consists of ten 10 950 m transects distributed throughout a
2-ha area that is chosen for homogeneity and to represent a given
forest habitat in a given region. UTM coordinates for each plot
(Universal Transverse Mercator system using WGS 1984 datum)
were collected using handheld Garmin 60csx units. Environmen-
tal variables describing climate, soil and forest structure were
used in order to define the environmental conditions of each
studied plot (for complete details, see Baraloto et al. 2011). Soil
physical and chemical descriptions were conducted on ten bulked
samples of surface soil (020 cm depth) collected throughout each
plot. Climatic variables were calculated using M
et
eo-France data
in French Guiana and from IIAP weather stations in Peru. Cli-
mate in the Guianas is driven by a marked seasonal alternation
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
228 G. P. A. Lamarre
between a wet season (December to August) and a dry season
(September to November). In French Guiana, the intertropical
convergence zone results in heavy rains with up to 120 mm on
some days in December to February and April to July. A marked
and short dry season in March is also characteristic of the Gui-
anas, in addition to a long dry period during August to Novem-
ber (Wagner et al. 2011). In contrast with the Guianas, there is
no distinctive dry season in northern Peru, although it also can
have short periods of heavy precipitation for several days (Mar-
engo 1998). Each habitat type was separated by 1 km to avoid
collecting specimens (i.e. avoiding the ‘tourist’ issue, see
Ødegaard 2004) from adjacent habitats.
sampling arthropod communities
Arthropod communities were sampled weekly in the twelve per-
manent plots from August to November 2010 in French Guiana
and between May and September 2011 in Peru, corresponding to
drier periods in each region. We employed a multiple trapping
method composed of two types of flight interception trap (FIT),
the malaise trap (MT) and the windowpane trap (WT); and two
types of attractive traps: the fruit trap (FT) and the automatic
light trap (ALT) (Fig. 1). For each plot, one pair of each FIT (2
MTs +2 WTs) and two pairs of FT were installed within the for-
est understorey of the 2-ha surface area covered. Malaise and
windowpane traps represent wide interception surfaces that are
together collecting a representative portion of flying arthropods
(Lamarre et al. 2012b). To capture multidirectional trajectories of
insects flying through the forest understorey, we installed one pair
of each MT and WT in or around gaps in each plot. These traps
were collected every 6 days during the study period in each
region.
Each fruit trap (4 FTs per plot) was installed and fixed in tree
branches between 3 and 5 m high and collected every 2 days.
These traps consist of a 1-m mosquito net cylinder in which a fer-
mented mixture of banana, sugar and rum actively attract fruit-
feeding butterflies and to a lesser extend nectar-feeding butterflies
and a few other taxa (i.e. grasshoppers, beetles and wasps).
Finally, we installed one portable automatic light trap (ALT)
with an 8-W backlight tube to collect light-attracted arthropods
during each new moon of the study period (+/2 days). We
installed ALTs in the middle of each plot and trapped for a total
of 24 sampling nights over the study period. Each of the trap
types was separated by at least 20 m to avoid spatial interference
both between and within traps. We employed equal sampling
effort in terms of number of daynight periods for each trap in
each plot and in each country.
taxonomic sorting and collections
For each plot (aggregating the collections of multiple traps),
adult arthropods including five important major insect orders in
Insecta (Coleoptera, Lepidoptera, Hemiptera, Hymenoptera and
Orthoptera) in addition to spiders (Araneae) were counted and
(a)
(b)
(c)(d)
(e)
Fig. 1. Sampling sites and trap methods installed in the Amazon Basin. (a) Map of the Amazon region with major watersheds, illustrat-
ing sites (circles) and plots (dots) established in the northern (Porvenir) and southern (Jenaro Herrera) regions of Loreto, Peru; and the
western (Laussat) and eastern (Regina) regions of French Guiana. (b) Automatic light trap. (c) Malaise trap. (d) The new type of
windowpane trap developed in French Guiana. (e) Aerial fruit trap.
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
Drivers of Amazonian arthropod assemblages 229
identified to the family level. This level of taxonomic resolution
has been found to be sufficient for detecting some significant pat-
terns of community composition and beta diversity in temperate
systems (Timms et al. 2013). Moreover, family-level identification
has provided ecologically adequate surrogates for species in the
study of functional diversity (see also Cardoso et al. 2011 for
both temperate and tropical systems). Because of strong diver-
gence in life histories within some family-level taxa, eight diverse
groups were sorted further to the subfamily level (Lawrence et al.
1999): Ceratocanthinae (Hybosoridae), Colydiinae (Zopheridae),
Malachiinae (Melyridae), Paussinae (Carabidae), Platypodinae,
Scolytinae (Curculionidae), Noctuinae (Erebiidae) and Scydmaen-
inae (Staphylinidae). Three hymenopteran taxa (Chalcidoidea,
Ichneumonoidea and Proctotrupoidea) could be identified only to
the super-family due to our inability to consistently separate them
further. Due to the lack of knowledge in identification and classi-
fication of some groups, we excluded all Diptera, Odonata and
specimens in small orders (Phasmatodea, Mantodea). Most speci-
mens in Gryllacrididae, Anostostomatidae, Rhaphidophoridae
and Gryllidae families (Orthoptera) were highly damaged because
of the windowpane trap collecting methods and were therefore
excluded from the analysis. Because of their important functional
role in ecosystems (Cardoso et al. 2011), we included spiders in
our sample and were able to capture a representative portion of
them with our flight interception traps (Vedel, Camus & Lamarre
2011). Samples were sent to taxonomists that are collaborating
along with the Soci
et
e Entomologique Antilles-Guyane (SEAG)
representing hundreds of taxonomists from institutes, universities
and museums world-wide. Distribution records were added to the
lists of French Guiana (SEAG, Labex CEBA) and Peru (IIAP
Iquitos).
arthropod functional classification
Each arthropod family was described using 21 functional and
ecological traits belonging to three trait categories (Table 1,
Appendix S3, Supporting Information). Based on these functional
attributes, we constructed a matrix of binary functional traits
using the literature (Gauld & Bolton 1988; Delvare & Aberlenc
1989; Browne & Scholtz 1999; Lawrence et al. 1999) and con-
firmed by experts of the SEAG network. First, in order to extend
the designation of arthropods into major ecological guilds, we
classified each group by its most frequent food source. Secondly,
we described the general type of insect mouthparts as a comple-
mentary measure of feeding mode and morphological feature that
emphasizes resource use. We recognize that insect mouthparts
represent a complex structure in which variation may be con-
tributed to by at least 34 fundamental mouthpart types (Laban-
deira 1997). Nevertheless, we chose to distinguish three major
types of mouthparts (siphoning, piercingsucking and mandibu-
lates) that represent the ecological attributes of insect feeding
strategy among our studied arthropod taxa. Thirdly, we described
the different habitats and microhabitats inhabited by each taxa.
We classified ‘free-living’ insects in this third category because
these taxa are believed to be ‘tourist insects’ as defined by Mor
an
& Southwood (1982), implying high mobility across a wide range
of habitats. Some generalization of ecological characteristics was
made because detailed trait information is not yet available for
some invertebrate taxa and/or not in South America. In some
cases, when information was missing in the Amazon for a given
family, we used the data available for the same family in another
part of the world or those available for other related taxonomic
group. Despite the coarse taxonomic resolution of our data set
(i.e. mostly family level), this approach focussed on resource-cap-
ture and resource-use traits that are expected to capture most of
the evolutionarily conserved functional attributes at the family
level (see Timms et al. 2013 for discussion on optimal taxonomic
resolution).
statistical analyses
A taxonomic approach was first constructed based on the sum of
the relative abundance of each collected arthropod taxa for each
plot (i.e. mostly at the family level, in addition to seven subfami-
lies and three super-families). Dissimilarity in community-level
arthropod abundance among plots that is community turnover
was measured using BrayCurtis indices. Correlations between
taxonomic arthropod dissimilarity among habitat and countries
were visualized with a NMDS ordination and tested for signifi-
cant differences among habitats and across country with analysis
Table 1. List of the 21 functional traits used in this study
Categories Functional traits Details
b
Feeding source Leaf Leaf-feeding insect
Sap Including phloem,
xylem and mesophyll
cell sucker
Wood-related Including decayed
vegetation
(saproxylophagous)
Invertebrates Predator and parasitoid
Organic matter Including dung
Fruit and Flower Including seed, nectar
and pollen feeder
Fungi-related Fungivore
Scavenge Insects that scavenge
as resource-use
Mouthparts Mandibulates An insect having mandible
Piercingsucking Insect with mouthpart
modified for piercing
and sucking
Siphoning Insect with mouthpart
modified for siphoning
Habitats Terrestrial Insects that have
terrestrial habit
Aquatic Insects that have aquatic
or semi-aquatic habit
Riparian Living in river shore, sand
and muddy habitat
Litter Insects inhabiting the first
layer of soil profile
Wood Xylophage insects including
insect inhabiting under bark
Endophagy Insects performing leaf
mining, stem boring,
gall forming
Dead tree Decaying wood
Free-living Defined as ‘tourist’ insect
a
Dung and carrion Insects inhabiting dung
and carrion matter
a
Definition from Mor
an & Southwood (1982)
b
We tried to add all details concerning functional attributes for
both adult and larvae when information was available.
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
230 G. P. A. Lamarre
of variance (ANOVA on NMDS coordinates). We then explored
how arthropod taxa differ in abundance among the three differ-
ent forest habitats and between countries. The impact of habitats
and countries was modelled using a generalized linear model
framework. Because our response variable, that is the number of
individuals recorded in a plot, was discrete with positive values,
we modelled them with a Poisson distribution. The significance of
both habitat and country effects was assessed through the Wald
statistic Z (R software; R Development Core Team, 2013):
log E Indch
ðÞðÞ¼h0þhcþhh
where Ind
ch
is the number of individuals of a given taxa in coun-
try cand habitat hand hthe model parameters. To counteract
the problem of multiple comparisons, we used the HolmBonfer-
roni method (Holm 1979) to correct the significance values.
Secondly, in order to evaluate the degree of arthropod habitat
associations across the studied forests, we calculated indicator
taxa values (IndVal) for each arthropod taxon after Dufrene &
Legendre (1997).
The trait-based approach integrated the matrix of 21 functional
traits (Table 1) to create a pairwise functional dissimilarity matrix
for the studied plots. Functional distances between all taxa were
computed according to their trait value using the Gower’s metric
(Gower 1966). Then, we constructed a functional typology of the
overall arthropod community using Ward’s method (Everitt et al.
2011). We then computed the KGS penalty function (Kelley,
Gardner & Sutcliffe 1996) to decide where to prune the tree in
order to delimit arthropod functional groups. The minimum of
this function represents the suggested pruning size. The consis-
tency of each arthropod taxon’s membership to a given func-
tional group (i.e. suggested pruning) was computed and validated
using a silhouette plot (Rousseeuw 1987). We then tested for dif-
ferences in functional group abundances among the three habitats
using a GLM Poisson model in the same way as for the taxo-
nomic approach.
Finally, we partitioned the degree to which spatial variation in
community composition (taxonomic and functional group com-
position) was explained by environmental and geographical com-
ponents using a canonical partitioning procedure (Legendre,
Borcard & Peres-Neto 2005). We used geographical distances
between pairs of plots calculated from the UTM coordinates of
each permanent plot. An environmental distance matrix of the 24
environmental variables (i.e. forest stand, climatic and edaphic
variables, see Baraloto et al. 2011) was calculated for each plot
pair following a principal component analysis of the environmen-
tal data set of the entire 74 plot network. We first calculated two
principal coordinates of neighbour matrices (PCNM), the first
one on the community composition and the second one on the
geographical distance matrices. We then extracted the first five
eigenvectors of each PCNM and used these eigenvectors in two
partial constrained correspondence analyses (pCCA), the first in
which community composition was constrained by environmental
eigenvectors while partitioning out the effect of geographical
eigenvectors, and the second in which community composition
was constrained by geographical eigenvectors while partitioning
out the effect of environmental eigenvectors. We were able to
partition the variance in community composition that is solely
attributable to environmental effects, to geographical effects and
to ‘shared’ variation among environment and geography
(Table 2).
Results
changes in arthropod taxonomic composition
In total, 60 123 specimens of arthropods were collected
and assigned to 147 taxonomic groups, representing 108
super-families in seven arthropod orders (Appendix S1).
Variance partitioning showed that geographical distances
and environmental dissimilarity among plots explained
most of the variation in arthropod community taxonomic
composition (Table 2). Geographical distance (controlling
for environment) explained slightly more (39% vs 34%)
of the variation in community composition than environ-
mental distance (controlling for geography).
These results can be visualized in the ordinations pre-
sented in Fig. 2, which show a clear separation in arthro-
pod composition between SF forest and the two other
forest habitats (axis 2; F
(1, 6)
=418; P=00003). We also
Table 2. Partitioning the effect of environment and geography on variation in arthropod community taxonomic and functional composi-
tion. We used partial canonical correspondence analyses. A first correspondence analysis (CA) was run on the taxonomic and functional
composition matrices to quantify all variation in the data. Then, canonical correspondence analyses (CCA) were run to decipher the part
variance that can be explained by one constraint (environment or geography) while controlling for the other. The first 5 axes summarize
more than 99% of the observed variation in constraints
Inertia
a
Axis 1
b
Axis 2
b
Axis 3
b
Axis 4
b
Axis 5
b
MSC
c
Taxonomic composition
CA 088
CCA Environment 030 011 007 006 003 002 343%
CCA Geography 035 012 010 008 0003 002 393%
Functional composition
CA 027
CCA Environment 012 010 001 001 000 000 426%
CCA Geography 007 003 003 001 000 000 260%
a
sum of eigenvalues.
b
eigenvalues.
c
MSC =(inertia of CCA/inertia of CA)*100; it provides an indication of the proportion of the variance accounted for by environment
or geography.
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
Drivers of Amazonian arthropod assemblages 231
found convergent patterns of dissimilarity among habitat
types between Peru and French Guiana. In particular,
overall community composition in SF forest was remark-
ably similar in the two countries, mainly because of a
consistent dominance of aquatic insect communities in
these habitats (Appendix S1 and Table 3). We observed a
high similarity in taxonomic composition in terra firme
clay forest and to a lower extent in white-sand forest
habitats within each country (Fig. 2). Taxonomic compo-
sition was strongly and significantly differentiated between
Peru and French Guiana (axis 1; F
(1, 6)
=2004;
P<0001). The partitioning analysis clearly showed that
the effect of geographical variation in community taxo-
nomic composition was stronger than the effect of envi-
ronment (Table 2), a pattern also confirmed by the visual
inspection of the NMDS ordination.
arthropod habitat associations
Overall, arthropod taxa exhibited striking contrasts in
habitat associations across the studied forest communities,
with more than 17% (26 out of 147) of arthropod taxo-
nomic groups having significant preferences for a single
habitat type (Table 3). Arthropod families that showed
clear habitat associations were mostly detected in high-
resource habitats (e.g. TF and SF). Nevertheless, white-
sand forest communities were preferred habitats for two
moth families (Dalceridae and Nolidae), in addition to
two Auchenorrhyncha families (Delphacidae and Fulgo-
ridae). Ground beetles (i.e. Carabidae) were the beetle
family exhibiting the strongest association with a partic-
ular forest habitat, with nearly two-thirds of all individ-
uals collected in SF forests. We also found that more
than 60% of the individuals in Mordellidae flower bee-
tles were collected in TF forest (see Table 1). These
patterns are consistent with the results of the general-
ized linear model (Appendix S1) in which we found
Fig. 2. Non-metric dimensional scaling
(NMDS) ordinations illustrating similarity
in arthropod taxonomic composition
among plots of different habitats, regions
and countries. French Guiana plots are
coloured in blue and Peruvian plots in
red. Habitats include terra firme clay for-
est (circles), white-sand forest (triangles)
and seasonally flooded forest (squares).
Light and dark blue symbols represent the
Laussat and Regina regions of French
Guiana, respectively. Light and dark red
symbols represent the Porvenir and Jenaro
Herrera regions of Peru, respectively (see
Fig. 1). The colour version of this figure is
available online.
Table 3. Arthropod taxa with significant associations with each
of the studied forest habitats. Indicator taxa values after Dufrene
& Legendre (1997) and the probability of obtaining as great an
indicator value as observed over 1000 iterations
Order Taxa
Preferred
forest
habitat
Indicator
value P
Coleoptera Carabidae Flooded 0738 0007
Coleoptera Cicindelidae Flooded 0912 0013
Coleoptera Heteroceridae Flooded 0891 0013
Coleoptera Hydrophilidae Flooded 0805 0016
Coleoptera Hydrochidae Flooded 0864 0019
Coleoptera Dytiscidae Flooded 0967 0066
Hemiptera Gerridae Flooded 0933 0006
Isoptera Termitidae Flooded 0852 0008
Lepidoptera Hesperiidae Flooded 0593 0047
Coleoptera Scarabaeidae terra firme 0681 0007
Coleoptera Ptilodactylidae terra firme 0588 0019
Coleoptera Nitidulidae terra firme 063 0038
Coleoptera Phengodidae terra firme 07005
Coleoptera Curculionidae terra firme 0483 0067
Coleoptera Erotylidae terra firme 0579 0089
Coleoptera Mordellidae terra firme 0656 0006
Hemiptera Cicadellidae terra firme 046 0071
Hemiptera Flatidae terra firme 070073
Lepidoptera Nymphalidae terra firme 0496 001
Lepidoptera Saturniidae terra firme 0611 001
Orthoptera Acrididae terra firme 0567 002
Araneae Salticidae terra firme 0634 0045
Hemiptera Delphacidae White sand 0824 0013
Hemiptera Fulgoridae White sand 081 0019
Lepidoptera Dalceridae White sand 1 0007
Lepidoptera Nolidae White sand 0675 0059
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
232 G. P. A. Lamarre
that 82 out of 147 taxonomic groups (i.e. 558 %) dif-
fered significantly in their abundance among the three
studied forest habitats.
changes in arthropod functional composition
The functional typology of the 147 taxa identified seven
distinct functional groups (Fig. 3), or clusters of taxo-
Fig. 3. Cluster functional dendrogram of
the overall arthropod community. Results
for the functional-based approach inte-
grated the matrix of 21 functional traits to
create a pairwise functional dissimilarity
matrix. Functional distances between all
taxa were computed according to their
trait value using the Gower’s metric.
Arthropod orders are coloured to visualize
phylogenetic conservatism in functional
attributes; red =Hemiptera, green
=Coleoptera, blue =Lepidoptera, yel-
low =Araneae, orange =Orthoptera, bla
ck =Hymenoptera, purple=Scutigeromor-
pha and burgundy =Isoptera. The colour
version of this figure is available online.
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
Drivers of Amazonian arthropod assemblages 233
nomic groups sharing similar ecological and functional
attributes and that are therefore likely to be similar in
their response to their environment and/or their effects on
ecosystem functioning (Diaz & Cabido 2001). Figure 3
illustrates the clear separation between arthropod groups
related to leaf resources (groups 1 and 4), those repre-
sented by predators and parasitoids (groups 2 and 3) and
those feeding on wood and fungi (groups 5 and 6). Our
approach also discriminated different feeding sources (e.g.
groups 1 and 4 feed on leaf tissue) from morphological
traits related to foraging (hemipterans from Group 1 but
also Group 2 harbour the same piercingsucking stylet).
Each of the seven functional groups had contrasting
distributions across the three forest habitat types (Fig. 4).
Most groups exhibited higher abundance in high-resource
environments (i.e. SF and/or TF). Herbivores (leaf feeders
(a)
(b)
(c)
(e)
(f)
(g)
(d)
Fig. 4. Relative abundances of arthropod functional groups differ among contrasted types of habitats (TF =terra firme clay forest,
SF =seasonally flooded forest, WS =white-sand forest). (a) Sap-sucker; (b) leaf-feeder; (c) woodfungi feeder; (d) mixed beetle; (e)
aquatic beetle; (f) hemipteran predator (+Araneae) and (g) insect predator and parasitoid. Different letters indicate significant differences
in mean abundance among habitats at P<005.
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
234 G. P. A. Lamarre
and sap suckers), mixed beetles and insect predators
showed a higher abundance of individuals in TF than in
both SF and WS forests. Woodfungi feeders and aquatic
insects were most abundant in SF forests.
Variance partitioning showed that geographical distance
and environmental dissimilarity among plots also
explained most of the variation in arthropod community
functional composition (Table 2). However, functional
composition was much more clearly linked to environ-
mental effects than to geographical distance. Geographical
distance (controlling for environment) explained only
26% of the variation in community functional composi-
tion, whereas environmental distance (controlling for
geography) explained 43% of variation in arthropod com-
munity functional composition.
Discussion
habitat filtering shapes arthropod
taxonomic composition
In our study, arthropod community composition varied
markedly across contrasting tropical forest habitats. This
strong pattern of turnover among habitat types is concor-
dant with the few previous studies of arthropod commu-
nity composition in tropical forests (Smith, Hallwachs &
Janzen 2014). For instance, Novotny et al. (2005) found a
high turnover in caterpillars associated with the host plant
genus Ficus along altitudinal gradients. Rodriguez-Cas-
ta~
neda et al. (2010) also found high beta diversity in both
plant and insect communities across a tropical montane
gradient in four distinct elevation zones (see also Smith,
Hallwachs & Janzen 2014 for ants). Our study therefore
confirms that marked shifts in environmental conditions
can strongly influence spatial patterns in arthropod com-
munities, here in lowland Neotropical forests. We sampled
a limited number of sites as comprehensively as possible.
Nevertheless, our statistical approach allowed us to com-
pare the relative contributions of geography and environ-
ment in shaping arthropod community composition,
which were relatively equal and explained most of varia-
tion (Table 2).
The low overlap in overall arthropod composition
between highly contrasted forest habitats may be driven
by differences in habitat structure, changes in host plant
species richness and composition and host plant func-
tional traits. The three forest habitats we studied differ
markedly in forest structure and soil texture and fertility
(Baraloto et al. 2011), with potential consequences for
arthropod community composition. For instance, forests
with less limiting mineral nutrients and a more rapid turn-
over of plant tissue (Lamarre et al. 2012a, 2014) support
higher abundances of herbivorous insects and associated
predators. A recent study showed that a single tree species
may host different assemblages of insect herbivores in
white-sand and terra firme sites and that this pattern
might be directly linked to variations in soil nutrient
availability (Fine et al. 2013). Because of higher resources
and presumably greater niche partitioning (food, seasonal-
ity and space), we also found significant differences in cas-
cading trophic level structure with higher abundances in
high-resource habitats than low-resource habitats (e.g.
white-sand forest). For example, rove beetles (Staphylin-
idae) had nearly five times more individuals in high-
resource habitats (both SF and TF) than in white-sand
forests (Appendix S1).
Previous studies have shown that plant species composi-
tion shows strong turnover among local communities
(Tuomisto et al. 2003) and across different habitats types
in the Amazon (Fine et al. 2010). Indeed, each habitat
considered in our study harbours a unique floristic com-
position (Baraloto et al. 2007; Fine et al. 2010) that
includes many habitat specialists (Lamarre et al. 2012a).
Finally, we believe that host plant functional traits may
be influencing herbivore community structure. Leaf traits
promoting higher resource conservation are expected in
low-resource habitats, whereas terra firme tree species are
allocating, in turn, more resources into growth with
higher specific leaf area and higher nutrient concentra-
tions (Baraloto et al. 2010; Fortunel et al. 2014; Lamarre
et al. 2014). We would therefore expect strong turnover in
arthropod communities dependent on plant community
composition, especially host-specialist herbivores (Nov
otny et al. 2006). In general, we found a high turnover of
arthropod communities across forest communities with
different floristic composition (Fine et al. 2010). For
instance, leaf beetle (Chrysomelidae) and weevil (Cur-
culionidae), which are the most diverse insect families,
support, respectively, 27 and 21 more individuals in TF
forests than in WS forests (Appendix S1). Furthermore,
moth and butterfly communities also showed striking dif-
ferences in abundance between habitat types with a clear
dominance in high-resource habitats (for Nymphalidae,
Notodontidae, Saturniidae, Sphingidae and Noctuidae).
arthropod habitat association
Most arthropod families in both regions showed striking
differences in their relative abundances among the three
studied habitats. In particular, we found strong differ-
ences in arthropod composition between seasonally
flooded forests and the two other forest habitats (Fig. 2).
In particular, the ground beetle family (Carabidae) exhib-
ited 43 more individuals in SF than in TF forests
(Appendix S1). Seasonally flooded forests exhibited a con-
vergent effect on overall community composition that was
remarkably similar in the two countries. A recent study
found a high rate of treefall disturbances in French Guia-
nan flooded forests, resulting in a more rapid forest turn-
over than in terra firme forests (Ferry et al. 2010). We
speculate that the more rapid forest dynamics in flooded
forests may increase resources available for specific feed-
ing guilds such as predators. Disturbance caused by
water-table fluctuation in seasonally flooded forests is
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
Drivers of Amazonian arthropod assemblages 235
likely to influence arthropod community composition
(Ellis et al. 2001; Baccaro et al. 2013). Additional expla-
nations to the trend observed may lie in physiological
stressors among host plant assemblages subjected to regu-
lar flooding regimes that may drive herbivore and associ-
ated higher trophic level in lowland tropical forests.
towards a functional classification of
tropical arthropods
Several authors first described the guild concept for
arthropods based on feeding strategy (Mor
an & South-
wood 1982). As a novel application to the feeding guild
approach, we propose a functional composition approach
based on feeding, habitat and mouthpart traits that are
inherent to each arthropod family. Although we recognize
that the functional traits assigned in our study (e.g. at the
family level) may be a simplistic representation of insect
ecological niches, we believe this is a novel approach that
may help investigating arthropod community patterns.
Based on trait-based similarity, each of the 147 taxa was
classified and grouped into seven functional groups. The
visual inspection of the silhouette plot, a graphical aid for
validation of cluster analysis, showed high consistency of
affiliation for each taxon within each functional group
(Appendix S2). Such a functional tree can be considered
as a first step towards describing more accurately the roles
of arthropods in ecosystem functioning. For instance, the
functional clustering obtained from our data set highlights
that Coleoptera (in green), one of the most diverse groups
of arthropods, comprise taxa with highly contrasting
functional roles in lowland tropical forests. We believe
that a refined approach to functional characterizations
(Flynn et al. 2009; Moretti et al. 2009), in concert with
phylogenetic data (Smith, Hallwachs & Janzen 2014;
Lamarre et al. in press), will allow enhancing and gen-
eralizing this functional approach for future studies of
arthropods.
contrasting functional composition across
lowland tropical forests
Overall, our functional approach using simple functional
and ecological traits at the family level reveals strong pat-
terns of dissimilarity in functional structure among
arthropod communities collected in terra firme, flooded
forest and white-sand forest plots (Fig. 4). Environmental
filtering should translate taxonomic turnover into func-
tional turnover across these steep habitat gradients (e.g.
low functional redundancy, see Flynn et al. 2009; but see
Vill
eger et al. 2012). In our study, we observed that taxo-
nomic turnover was accompanied by marked changes in
functional composition. Most of the functional groups
showed greatest abundance in high-resource habitats com-
pared to low-resource habitats (Fig. 4). This result is con-
sistent with previous studies that have reported greater
herbivory rates in high-resource habitats (Fine et al. 2006;
Lamarre et al. 2014). For example, insects associated with
wood and fungi resource uses are found to be more com-
mon in seasonally flooded forest, in which more forest
dynamics, microclimate (e.g. moisture) and natural pertur-
bation occur and are favourable for specific insect guilds.
Our results are thus consistent with recent research con-
ducted in some of the same forest sites that showed a sig-
nificantly lower wood density in seasonally flooded plant
specialists (Fortunel et al. 2014). The pattern found on
functional Group 5 (see Fig. 3) would not have been
detected unless using a functional approach (Group 5
includes 21 taxonomically distinct beetle families).
The strength of environmental filtering on functional
community composition may be even stronger because we
included white-sand forests that are characterized by vege-
tation with pronounced sclerophylly, low diversity and
high endemism in plant species (Medina, Garcia & Cue-
vas 1990; Fine et al. 2010). We predicted that a unique
assemblage of insect herbivores would be able to feed on
the thicker and tougher leaves, for example the white-sand
habitat specialists such as Delphacidae and Fulgoridae
(Table 3). Our functional approach confirmed this gener-
ally as we found that functional composition in leaf-
chewer and sap-sucker taxa clearly differed in relative
abundance among the three contrasted habitats with a
higher abundance in terra firme clay forest (Fig. 4 and
Table 2). A high allocation to secondary compounds
restricts the relative abundance of leaf and sap feeders,
and these properties are more characteristic of white-sand
forests (Coley, Bryant & Chapin 1985; Fine et al. 2006).
Further investigations are needed on the functions of dif-
ferent plant tissues (resource conservation and/or defence)
that would allow us to test whether plant functional
trade-offs are directly influencing arthropod functional
community structure in tropical forests. We envision a
bottom-up model by which herbivore species and associ-
ated natural enemies are filtered among habitat types
based on shifts in host plant community functional com-
position correlated with environmental changes.
partitioning effects on arthropod community
composition
The NMDS ordination clearly suggests that arthropod
taxonomic assemblages are partitioned in two regions,
Loreto, Peru, and French Guiana, representing distinct
biogeographical regions that differ in geological and
edaphic histories in addition to highly contrasted rainfall
seasonality (Hoorn et al. 2010). The considerable turnover
found between countries is also consistent with the results
of the generalized linear model in which we found that
nearly 47% of the arthropod taxonomic groups (69 out of
147) differed significantly in their abundance between
French Guiana and Peru (Appendix S1). We believe this
pattern is particularly evident because of the contrast in
soil profiles at both ends of the Amazon that are expected
to influence both host plant and associated arthropod
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
236 G. P. A. Lamarre
community composition (Radtke, da Fonseca & Wil-
liamson 2007; Lamarre et al. in press). In our study, we
attempt to quantify the degree to which the effect of envi-
ronment and geography explain the variation in commu-
nity composition using both taxonomic and functional
approaches (Table 2). Our results showed that the varia-
tion in community taxonomic composition is explained by
both geography and the environment while community
functional composition is chiefly explained by the effect of
environment. Very few studies have disentangled the rela-
tive contribution of biogeographical processes driving
community composition in tropical arthropods, and the
study of several additional sites would be required to
understand general patterns of biogeographical processes
driving arthropod composition. This result is rather inter-
esting as the strong turnover found between French Gui-
ana and Peru may be explained by the Amazonian rivers
and Guiana shield that act as a major barrier to dispersal
(Wallace 1852). Furthermore, the variation in community
functional composition is largely driven by the environ-
ment (43% of the variance explained), a pattern consis-
tent with the greatest abundance of functional groups
found in high-resource habitats (Fig. 4). This finding rein-
forces the idea that habitat filtering is shaping functional
attributes in arthropod assemblages that allow a species
to persist (or not) in a given habitat and confirms the
importance to attempt arthropod functional classification
across contrasting tropical rain forests.
conclusion
Our broad sampling approach in concert with the first
attempt of arthropod functional classification reveals the
importance of environmental filtering and biogeographical
processes in shaping patterns of arthropod community
assembly in lowland Amazonian forests. Multiple taxo-
nomic groups share similar functions in these forests, and
functional groups have markedly different abundances
across habitat gradients. Nevertheless, we recommend
more detailed taxonomic information in such broad sur-
veys across multiple sites and for refined descriptions of
important functional traits across arthropod groups. We
believe this will require improved collaborations between
taxonomists and ecologists. Further coordinated study
will be necessary to examine the consistency of patterns
we observed by combining mass sampling, metabarcoding
and host specialization approaches across multiple habi-
tats throughout tropical regions that differ in seasonality
and geological history. Then, we will be able to more pre-
cisely disentangle biogeographical processes and environ-
mental determinants that drive regional patterns of
arthropod diversity across tropical forests.
Acknowledgements
We thank the many colleagues and friends who participated in the field
work in Peru: Julio Sanchez, Julio Grandez, Magno V
asquez Pilco, Mila-
gros Ayarza Zuniga and Cyrus Harp; and in French Guiana: Anthony
Percevaux, Xavier Leroy, Benjamin Leudet, Benoit Burban, Jean-Yves
Goret and Jocelyn Cazal. We also thank taxonomists from the Soci
et
e
Entomologique Antilles-Guyane for their help during identification, in par-
ticular Robert Constantin, St
ephane Br^
ul
e, Fr
ed
eric B
en
eluz, Philippe Col-
let and Marc Tussac. We thank the Direction of Areas Naturales
Protegidas y Fauna Silvestre (INRENA) which provided necessary permits
for study and exportation of specimens and the Jefatura de la Reserve
Nacional Allpahuayo-Mishana (005-2011-SERNANP-RNAM-J, permiso
de exportaci
on 006736). We also thank C
esar A. Delgado Vasquez and
Jos
e
Alvarez Alonzo from Instituto de Investigations de la Amazonia
Peruana (IIAP) for logistical support to work in and around the Esta-
ci
ones Allpahuayo-Mishana and the Centro de Investigation Jenaro Her-
rera. Thibaud Deca
ens, S
ebastien Vill
eger and Vojtech Novotny gave
valuable comments to previous drafts of this paper. Research was sup-
ported by a collaborative NSF grant (DEB-0743103/0743800) to C. Bar-
aloto and P.V.A. Fine, the Fond Social Europ
een (FSE) to G.P.A.
Lamarre and an INRA Package grant to C. Baraloto. This work has bene-
fited from an ‘Investissement d’Avenir’ grant managed by Agence Natio-
nale de la Recherche (CEBA, ANR-10-LABX-25-01).
Data accessibility
All data for relative abundance of the taxonomic groups in each
habitat are listed in Appendix S1. Data are available from the
Dryad Digital Repository http://dx.doi.org/10.5061/dryad.mv60m
(Lamarre et al. 2015).
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Supporting Information
Additional Supporting Information may be found in the online version
of this article.
Appendix S1. Arthropod taxonomic structure illustrated by the
total abundance in each habitat and country.
Appendix S2. Silhouette plot showing the consistency of each
arthropod taxon memberships into each of the seven arthropod
functional clusters.
Appendix S3. Taxon-by-functional-trait matrix (supplementary
data in an online Excel file)
©2015 The Authors. Journal of Animal Ecology ©2015 British Ecological Society, Journal of Animal Ecology,85, 227–239
Drivers of Amazonian arthropod assemblages 239
... Terra firme forests are the most widespread forest type in the Amazon Basin while FP forests are riparian forests subject to episodic inundations by adjacent rivers during periods of high precipitation or upland Andean precipitation and/or snowmelt (Prance 1979;Junk et al. 1989;Worbes 1997;ter Steege et al. 2000;Parolin et al. 2004;Junk and Piedade 2010;Myster 2014Myster , 2016. Previous studies show that both forest types are rich in species but TF forests are generally more species rich than FP forests for many taxa (Campbell et al. 1986;Balslev et al. 1987;Gascon et al. 2000;Haugaasen and Peres 2005;Myster 2016;Bredin et al. 2020) including arthropods: spiders (Höffer 1997), ants (Wilson 1987;Majer and Delabie 1994;Mertl et al. 2009), canopy arthropods (Erwin 1983a;Adis et al. 1984Adis et al. , 2010 and terrestrial arthropods in general (Adis 1997;Adis and Junk 2002;Lamarre et al. 2016). However, only a relatively small amount of comparative data is currently available in Amazonian forests, particularly for groups of understory Coleoptera (Adis and Junk 2002). ...
... Few ecological studies have compared understory arthropod diversity and species assemblages from different forest types within Amazonia (Adis 1981;Pearson and Derr 1986;Majer and Delabie 1994;Zerm et al. 2001;Mertl et al. 2009;Lamarre et al. 2016;Santos-Silva et al. 2018). Even fewer report forest understory diversity and community data for the highly diverse Carabidae (Irmler 1979a, b;Zerm et al. 2001;Lamarre et al. 2016;Cajaiba et al. 2018), which includes a range of trophic roles including predaceous, predominately phytophagous and omnivorous species as well as some with specialized modes of nutrition (Thiele 1977;Lövei and Sunderland 1996). ...
... Few ecological studies have compared understory arthropod diversity and species assemblages from different forest types within Amazonia (Adis 1981;Pearson and Derr 1986;Majer and Delabie 1994;Zerm et al. 2001;Mertl et al. 2009;Lamarre et al. 2016;Santos-Silva et al. 2018). Even fewer report forest understory diversity and community data for the highly diverse Carabidae (Irmler 1979a, b;Zerm et al. 2001;Lamarre et al. 2016;Cajaiba et al. 2018), which includes a range of trophic roles including predaceous, predominately phytophagous and omnivorous species as well as some with specialized modes of nutrition (Thiele 1977;Lövei and Sunderland 1996). Current knowledge of Amazonian carabids in the understory of FP forests is largely based on research within Central Amazonia where flooded forests are annually inundated by several meters of water for several months a year (Irmler 1979a, b;Adis 1981;Paarmann et al. 1982;Zerm et al. 2001). ...
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... Each Identifying thousands of individuals and taxa represents a significant challenge for arthropod assemblage investigation. Researchers suggest order (Biaggini et al., 2007), family (Høye et al., 2021;Lamarre et al., 2016;Timms et al., 2013) or genus (Souza et al., 2016) as the most cost-efficient identification levels. We adopted a multiple resolution strategy to identify arthropods. ...
... In this study, we collected diversified arthropod samples composed of many taxonomic and functional groups (Lamarre et al., 2016). We expected to find differences in the abundance, diversity and taxonomic composition of arthropods between major studied habitats as documented from the study region (Didham, 1997;Vasconcelos & Bruna, 2012) and other parts of the Amazon (Barlow et al., 2007;Cajaiba & Silva, 2017). ...
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The diversity and phylogenetic community structure of many organisms is negatively affected by factors that covary with elevation. On the Pacific slope of the Cordillera Guanacaste within Area de Conservación Guanacaste (ACG) in northwestern Costa Rica we found a negative relationship between elevation and ant diversity on each of three volcanos. This pattern was evident when diversity was measured through molecular operational taxonomic units (MOTU) or by phylogenetic diversity (PD) based on DNA barcodes or a multi-gene phylogeny. We observed an asymmetrical mid-elevation peak at approximately 600–800 m and we found high species turnover between sites on the same mountain and among the three mountains. At the highest elevation cloud forest sites we found evidence of significant phylogenetic clustering, the expected result of environmental filtering. The narrow elevational range of each species, coupled with the high diversity at each sampling point, emphasizes that climate change will bring strong changes in the location and composition of biodiversity on these mountains. The structure and composition of the hyperdiverse communities present at any one elevation is extremely vulnerable to a changing climate.
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Cluster analysis comprises a range of methods for classifying multivariate data into subgroups. By organizing multivariate data into such subgroups, clustering can help reveal the characteristics of any structure or patterns present. These techniques have proven useful in a wide range of areas such as medicine, psychology, market research and bioinformatics. This fifth edition of the highly successful Cluster Analysis includes coverage of the latest developments in the field and a new chapter dealing with finite mixture models for structured data. Real life examples are used throughout to demonstrate the application of the theory, and figures are used extensively to illustrate graphical techniques. The book is comprehensive yet relatively non-mathematical, focusing on the practical aspects of cluster analysis. Key Features: textbullet} Presents a comprehensive guide to clustering techniques, with focus on the practical aspects of cluster analysis. textbullet{ Provides a thorough revision of the fourth edition, including new developments in clustering longitudinal data and examples from bioinformatics and gene studies textbullet Updates the chapter on mixture models to include recent developments and presents a new chapter on mixture modeling for structured data. Practitioners and researchers working in cluster analysis and data analysis will benefit from this book.
Article
Terrestrial arthropod communities remain poorly described for riparian ecosystems of the arid southwestern United States, and the effects of extensive river regulation and habitat alteration on these potentially important invertebrates are largely unknown. Beginning in 1991, surface-active arthropods were trapped at two riparian sites along the Rio Grande, in central New Mexico, for 2 years. One site was then experimentally flooded from mid-May to mid-June for each of the next 3 years to simulate historic, low intensity flooding, after which arthropod collections were continued. These primary sites. located outside the riverside levee, and isolated from flooding for about 50 years prior to the experiment, were compared with a naturally flooded site and a second non-flooded reference. Experimental flooding and observations of the naturally flooded site indicated that flooding did not affect total taxonomic richness, nor richness of spiders, beetles or ante. However, flooding may have slightly increased the number of carabid beetle taxa present. Flooding altered the overall composition for all taxa, insects, beetles and carabid beetles. Spider taxa composition may be insensitive to flooding, while ant responses were not clear. Abundance of terrestrial isopods and spiders decreased after flooding, while overall beetle abundance did not change. Abundance of crickets and carabid beetles increased, but the response was delayed until after the second flood. Changes in taxa composition and abundance after experimental flooding were generally consistent with arthropod community structure observed at a nearby naturally flooded site. This similarity suggests that reorganization of the terrestrial arthropod community may follow restoration of flooding to this riparian ecosystem. Copyright (C) 2001 John Wiley & Sons, Ltd.
Article
The degree of herbivory and the effectiveness of defenses varies widely among plant species. Resource availability in the environment is proposed as the major determinant of both the amount and type of plant defense. When resources are limited, plants with inherently slow growth are favored over those with fast growth rates; slow rates in turn favor large investments in antiherbivore defenses. Leaf lifetime, also determined by resource availability, affects the relative advantages of defenses with different turnover rates. Relative limitation of different resources also constrains the types of defenses. The proposals are compared with other theories on the evolution of plant defenses.
Article
(1) Comparative knockdown samples of the invertebrate fauna in trees were taken during summer in South Africa and in Britain. Betula pendula, Quercus robur, Robinia pseudoacacia, Buddleia and Salix species were sampled in both countries; Erythrina caffra was sampled in South Africa only. (2) A total of 41 844 individuals were sorted and identified; only two of these were molluscs, the rest arthropods. (3) The composition of the arboreal guilds in analysed with respect to the numbers and proportions of families, species and individuals, and by biomass. (4) Taxonomic similarities in the arthropod faunas of trees are compared within and across countries. (5) The narrow-leaved flexible-stemmed, willows (Salix species) had a depauparate fauna and proportionately more phytophagous species than the broad-leaved trees sampled. (6) There was a striking uniformity in the proportion of predatory species recorded on all trees in both countries, and also a constant proportion of phytophagous species on different broad-leaved trees. The relative numbers of chewing and sap-sucking species were highly variable, but when summed resulted in proportionally uniform numbers of phytophagous species. These phenomena are discussed in the light of recent debate on patterns in community structure.
Article
Tree species from upper Rio Negro rain forests (tierra firme, tall Amazon caatinga, and bana) can be classified morphologically as sclerophylls. In some cases, as for Clusia spp., the structural characteristics fit the pachyphyll leaf type of Grubb. Nutrient content, specific leaf area, and leaf thickness of the species studied are comparable to those of sclerophylls from Mediterranean climates. In spite of their sclerophyllous structure, leaves of the species studied are relatively drought intolerant. During rainless periods leaf stomatal conductance decreases markedly avoiding development of large negative xylem pressures. Overheating is prevented by most species through pronounced leaf surface inclination. It is concluded that sclerophyllous structure is not necessarily an adaptation to drought, but is probably selected in nutrient poor environments. This conclusion supports evidence provided by several authors indicating that sclerophylls may gain predominance in P deficient soils in both humid and semi-arid areas.