Macroinvertebrate functional feeding groups in neotropical streams 233
Introduction
Identifying the environmental factors driving macro-
invertebrate community structure is an important area
of study in freshwater ecology. The infl uence of vari-
DOI: 10.1127/1863-9135/2007/0170-0233 1863-9135/07/0170-0233 $ 2.25
© 2007 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart
Longitudinal and altitudinal changes of macro-
invertebrate functional feeding groups in neotropical
streams: a test of the River Continuum Concept
Sylvie Tomanova1, Pablo A. Tedesco2, Melina Campero3, Paul A. Van Damme4,
Nabor Moya3 and Thierry Oberdorff5
With 3 fi gures, 2 tables and 1 appendix
Abstract: The River Continuum Concept (RCC) explains the structural and functional characteristics of stream
communities focusing on the gradually changing physical components from headwaters to downstream habitats of
streams and rivers. The global value of the RCC is still uncertain, possibly because physical factors (e.g., altitude
and then temperature, stream order, channel width) can vary differently in longitudinal river axes across the world.
Moreover, RCC predictions in relation to different physical factors have not been tested adequately in different
biomes, especially biomes outside of temperate North America. Here, we report on the functional structure of mac-
roinvertebrate communities in neotropical streams from Bolivia along a broad altitudinal gradient (from 1120 to
4300 m a.s.l.), aiming to understand how altitude can affect the longitudinal changes in functional feeding groups
(FFG) and richness predicted by the RCC. The RCC predictions for functional structure were not completely
matched when analyzing FFGs in relation to an index of longitudinal stream gradient. However, after remov-
ing the effect of altitude by using residuals from regressions between FFGs and altitude, FFG patterns matched
RCC predictions more closely. We detected signifi cant relationships between altitude and the relative abundance
of collector-gatherers, shredders and scrapers which may be related to changes in temperature, UV radiation and
canopy cover along the altitudinal gradient. Our results indicate that altitude combined with position along the
longitudinal gradient is an important factor governing the FFG structure of macroinvertebrate communities in
neotropical streams.
Key words: organism distribution, distance from source, width, slope, altitude, Amazon sub-basin, Bolivia.
Fundamental and Applied Limnology
Archiv für Hydrobiologie
Vol. 170/3: 233–241, November 2007
© E. Schweizerbart’sche Verlagsbuchhandlung 2007
ous abiotic factors has been highlighted by relating
them to taxonomic and functional community metrics
(see for review Power et al. 1988). As an integrating
framework, the River Continuum Concept (RCC)
(Vannote et al. 1980) is a widely used model for the
1 Authors’ addresses: Laboratory of Running Waters Biology, Masaryk University, Kotlářská 2, 61137, Brno, Czech Republic.
E-mail: sylvatom@seznam.cz
2 Institut d’Ecologia Aquàtica, Universitat de Girona. Campus de Montilivi E-17071 Girona, Spain. E-mail: pablo.tedesco@udg.es
3 Unidad de Limnología y Recursos Acuáticos, Universidad Mayor de San Simón, Casilla 5263, Cochabamba, Bolivia. E-mail:
camperop@supernet.com.bo (for MC); nabor_moya@yahoo.com.ar (for NB)
4 Asociación Faunagua, Sacaba-Cochabamba, Bolivia. E-mail: faunagua@yahoo.com
5 Institut de Recherche pour le Développement (UR 131), Département Milieux et Peuplements Aquatiques, Muséum National
d’Histoire Naturelle, 43 Rue Cuvier, 75231 Paris Cedex 05, France. E-mail: oberdorf@mnhn.fr
* Corresponding author, E-mail: sylvatom@seznam.cz

234 S. Tomanova et al.
interpretation of the structural and functional charac-
teristics of stream communities focusing on the gradu-
ally changing physical components from upstream to
downstream habitats of streams and rivers. The RCC
predicts that this continuous gradient of physical con-
ditions, mainly related to stream size (e.g., stream
width, stream discharge), affects types and availability
of food resources, which in turn, drive the shift in the
functional feeding groups (FFG) of macroinvertebrate
communities.
Studies from temperate streams and rivers have
often observed the FFG shifts predicted by the RCC
(e.g., Hawkins & Sedell 1981, Minshall et al. 1983,
Grubaugh et al. 1997, Rosi-Marshall & Wallace 2002).
However, various studies from other climatic zones
have found that the longitudinal distribution of FFG
fi tted, at best, only partially to the RCC (e.g., Dudg-
eon 1984 for Asia, Marchant et al. 1985 for Australia,
Miserendino 2004 for South America, Greathouse &
Pringle 2006 for Central America). Therefore, the glo-
bal value of the RCC is still uncertain and the factors
potentially responsible for the observed discrepancies
have not been explicitly identifi ed.
Studies have generally attempted to explain the
FFG variability using factors refl ecting the position
of sites along the longitudinal gradient (e.g., stream
width, stream order, and distance from source) or
sites’ food availability (e.g., fi ne and coarse organic
matter), also refl ecting longitudinal position (Naiman
et al. 1987). However, the RCC predictions for FFGs
could also be affected by stream specifi c ecological
processes like leaf litter inputs and decomposition
rates or periphyton production, themselves infl uenced
by various environmental factors. For instance, leaf
litter inputs depend on the density and type of veg-
etation which are mainly determined by temperature
and precipitation regimes (Kharkwal et al. 2005). Leaf
litter palatability for shredders depends, among other
factors (e.g., leaf hardness), on microbial coloniza-
tion of leaves, i.e., conditioning of leaves (Gessner et
al. 1999, Graça et al. 2001), which may increase with
water temperature (Irons et al. 1994, Fabre & Chau-
vet 1998) and eutrophication (Gulis & Suberkropp
2003). Finally, periphyton growth, infl uencing the
density of scrapers, depends on nutrients (e.g., Kim &
Richardson 2000, Larned & Santos 2000), light (e.g.,
Vinebrooke & Leavitt 1999, Kim & Richardson 2000,
Larned & Santos 2000) and water temperature (e.g.,
Phinney & McIntire 1965, Kishi et al. 2005). All these
factors can vary differently along longitudinal axes of
rivers across the world and may be responsible for the
observed discrepancies with the RCC predictions.
Altitude is usually related to several environmen-
tal factors such as temperature, land cover or oxygen
availability (Finn & Poff 2005). Altitude has been
widely linked to macroinvertebrate taxonomic vari-
ability in the tropical zone (e.g., Suren 1994, Jacobsen
et al. 1997, Sites et al. 2003), however, functional ap-
proaches are rare (e.g., Greathouse & Pringle 2006).
Since altitude is strongly related to temperature, light
(UV radiation) and canopy cover, variations in eco-
logical processes such as leaf litter inputs, decomposi-
tion rates and periphyton production can be expected
across a large altitudinal gradient. Then, if the RCC
predictions for FFGs are infl uenced by the leaf litter
inputs, decomposition rates and periphyton produc-
tion (see above) varying along the altitudinal gradient,
removing the infl uence of altitude could eventually re-
veal the expected RCC patterns.
This study aims to (1) test if the RCC can be ob-
served in neotropical zone and (2) to test if altitude
can mask the predicted functional variability along the
longitudinal river gradient. We tested this hypothesis
by analyzing the relationship between macroinverte-
brate FFGs and the longitudinal gradient in thirty sites
(altitude ranging from 1120 to 4300 m a.s.l.) in several
pristine streams and rivers of Bolivia. The RCC pre-
dictions were evaluated, before and after removing the
effect of altitude, using a synthetic factor (the fi rst axis
of Principal Component Analysis of distance from
source, slope and river width) as an index of position
along the longitudinal gradient
Material and methods
Study sites and data collection
Four previous studies of the same study scheme (Campero
1998, Claros 1999, Arévalo 2000, Tomanova & Usseglio-Po-
latera 2007) provided the macroinvertebrate assemblages data
Table 1. Mean, minimum and maximum environmental param-
eters of study sites; n (number of sites with available informa-
tion) is indicated only if different from 30.
Mean Min – Max
Altitude (m a.s.l.) 2519 1120 – 4300
Slope (%) 4.24 0.028– 14.4
Distance from source (km) 38.5 0.05 – 254
River width (m) 16.2 6 – 27.3
Temperature (°C) 13.8 6.4 – 21
Conductivity (µS cm–1) 211.6 7.7 – 1305.2
pH 7.7 6.9 – 8.5
Mean fl ow velocity (m s–1) (n = 28) 0.48 0.008– 1.59
Mean depth (cm) (n = 28) 22.1 10.8 – 36