Archaimbault, V

Dumas, P.

Fernandez, H.

Fossati, Odile

Rocabado, G

Usseglio Polatera, P.

Wasson, J.G.

Horizon / Pleins textes

Deriving life traits from habitat characteristics : 
an initial application for neotropical invertebrates
Traits de vie et caractéristiques mésologiques!: 
une première application aux invertébrés néotropicaux
O. Fossati  (1), P. Dumas(2), V. Archaimbault(3), H. Fernandez(4), 
G. Rocabado(5), J.G. Wasson(6) & P. Usseglio-Polatera(7)
(1) Correspondence: Odile Fossati, IRD-Université Lyon 1, Ecologie des hydrosystèmes 
fluviaux, 43, bd du 11 novembre 1918, 69622 Villeurbanne-Cedex - France 
<j.o.fossati@wanadoo.fr>
(2) Université de Toulouse - France <Pascal.Dumas@ecolog.cnrs.fr>
(3), (7) Université de Metz - France <usseglio@sciences.univ-metz.fr>
(4) Universidad Nacional de Tucuman - Argentina <hugof@selway.umt.edu> 
(5) Universidad La Paz - Bolivia <giovanna_rocabado@hotmail.com>
(6) Cemagref, Lyon - France <jean-gabriel.wasson@cemagref.fr> 
Abstract
Using invertebrate life trait!patterns as a biomonitoring tool for the assessment of human impact 
in rivers is a rising research field. Yet in tropical regions, the lack of detailed biological or 
ecological information results in great difficulties to document such traits. Herein, we propose 
an approach to infer ecological traits from habitat characteristics, using ecological profiles. The 
method was tested on river invertebrates from the Bolivian Amazon Basin, as a preliminary 
step prior to adapting this tool to the context of tropical rivers. 
Key-words 
Macroinvertebrates, Method, South America, Stream
Résumé
L’étude des traits de vie des organismes constitue une approche pertinente des perturbations 
auxquelles sont soumises les communautés aquatiques. Or, dans les régions tropicales en 
général, le manque de connaissances préalables sur l’écologie et la biologie des espèces 
constitue le plus souvent un obstacle à l’étude de ces traits. Dans cet article, nous posons les 
bases d’une approche permettant de déduire certains traits écologiques à partir des 
caractéristiques du milieu, en utilisant des profils écologiques. Cette méthode a été testée sur les 
invertébrés de rivières du bassin amazonien bolivien et constitue un premier pas vers 
l’adaptation de cette approche au contexte des zones tropicales. 
Key-words
Amérique du Sud, Cours d’eau, Macroinvertébrés, Méthode
Introduction
Assessing changes in biological communities in relation to environmental variations is a major 
issue in both theoretical and applied ecology, whatever the organisms or systems considered. 
For running waters, a great variety of approaches was thus developed to monitor species or 
community responses as bioindicators of ecosystem disturbance. Approaches are based on 
indicators species, taxonomic composition, community structure or a combination of these 
methods (see a review in Cairns & Pratt, 1993 for freshwater invertebrates). In addition to 
traditional methods based on taxonomic structure of biocenoses, alternative approaches 
focusing on life traits patterns emerged in the last decade, providing a more functional image of 
aquatic communities (e.g. the “River Habitat Templet” concept, Townsend & Hildrew, 1994, 
developed from the idea of Southwood, 1977). They relate functional groups derived from life 
history or other biological or ecological traits of species to spatial or temporal gradients of 
environmental variability. For freshwater macroinvertebrates, recent tests at various 
geographical and temporal scales provided encouraging results in temperate streams as trends 
in species traits along environmental gradients were often significant (Charvet et al., 1998, 
Townsend et al., 1997, Dolédec et al., 1999, Usseglio-Polatera et al., 2000). 
Although some studies have shown that genus and even family levels may be sufficient 
to explore the functional diversity of freshwater invertebrates (Bournaud et al., 1996, Dolédec 
et al., 1998), great difficulties still remain when biological features of taxa are poorly 
documented. In tropical regions, the knowledge of invertebrates traits is often limited by a 
crucial lack of specialistes and published data. This is why we looked for a field-based coding 
method, that would enable us to posterior fuzzy coding and multifactorial analysis comparable 
to those performed in Europe (e.g. Usseglio-Polatera et al., 2000).
Our aim is to explore the validity of a field-based, practical approach to document 
ecological traits of benthic macroinvertebrates. The macroinvertebrate fauna and the associated 
microhabitat variables were studied in non-impacted sites from the Bolivian Amazon Basin. 
Methods
For each taxon, ecological traits were derived from the ecological profiles (Godron, 1968, 
Guillerm 1971) and coded using an “affinity scale” to constitute a reference matrix.
Field sampling
Benthic macroinvertebrates were sampled with a 0.1 m2 surber net in 22 non-impacted rivers 
located in the Yungas region of the Bolivian Amazon Basin that constitute an homogeneous 
entity in terms of faunal and ecological characteristics (Wasson & Barrère, 1999). Fauna was 
identified to the family level. Thirty two taxa were collected in 125 samples (scarce taxa were 
omitted). At each site, six characteristics of mesohabitats (elementary units of a patch mosaic 
sampled by surber net) were investigated to document hydraulic characteristics (flow speed, 
water depth), sediment type (dominant superficial substrate, under-layer) and feeding resources 
(organic deposits, periphyton) of habitats. These parameters were separated into 21 categories 
(cf. Table 1). Data were collected in the context of the BIOBAB (IRD, Institut de Recherche 
pour le Développement - La Paz University) project.
Calculation of ecological profiles and coding
For a given taxon, ecological preferences related to a given environmental variable were 
expressed using the frequency distribution of this taxon among the categories describing the 
trait (Figure 1). As a result, ecological profiles were calculated as distributions of occurrence 
per category (i.e. percentages) in the samples. The resulting matrix of percentages was then 
transformed to obtain a final “!affinity matrix!” per taxon and per category on a narrower scale. 
Within each variable, percentages different from 0 were ranked and an affinity score of 1 was 
given to the lowest percentage above null. The affinity score of the next category was 
incremented by 1 point if the percentage difference with the previous category was greater than 
5 % or by 2 points if the difference was more than 30 % (empirical thresholds).
Results and discussion
The final matrix provided, for each taxon, an affinity score per category from 0 (indicating “!no 
affinity!”) to 5 (indicating “!very high affinity!” - Table 2). A first interpretation of the matrix 
can be found in the observation of the taxa with high affinity for some modality (codes 3 to 5 in 
Table 1). A quarter of the taxa had a high affinity with the absence of organic deposit!; 38 % 
prefered more than 50 % in periphyton cover!; 62 % in total had high affinity with cobbles or 
fine stones in surface while the affinities with the sublayer classes were weaker!; 41 % of the 
taxa had a stronger affinity with 30 - 49 cm.s-1!flow speed!; high affinities with water depths 
were always noted for less than 10 % of the taxa (Figure 2). Flow speed, dominant substrate 
and periphyton were the more discriminating parameters at mesohabitat scale.
Information about invertebrate taxa preferences for the six environmental variables 
considered can be derived from this matrix. In this preliminary work, ecological traits derived 
from field data were globally consistent with our ecological knowledge for the taxa. For 
examples, Simuliidae were clearly rheophilic and Oligochateta prefered finer substrates. 
The first tests using this matrix as a reference for various impacted sites from the same 
ecoregion (rivers from the Bolivian or the Argentinean Yungas) provided encouraging results. 
Contrasted patterns in species traits were observed among sites, and could be related in some 
cases to contrasted disturbance intensities. As an example, invertebrates known, in the same 
area of Bolivia, to be sensitive to suspended solids (Fossati et al., 2001) had higher affinities 
with abundant periphyton, which is limited by suspended solids (Fossati et al. publication in 
preparation).
In further studies, all the availble data for non-impacted sites will be used to code all the 
possible traits, in order to find which traits are really important. Moreover, we will better 
explore relationships between traits patterns and disturbance characteristics in order to better 
validate the reference matrix of taxa affinities for environmental features of habitats, and 
improve the coding process if possible.
When using the species trait approach in a biomonitoring context, a major disadvantage is that 
affinities of taxa for various traits have first to be documented. As a result, this approach is 
strongly dependent on the availability of biological information for taxa. Inferring ecological 
information (e.g. taxa “!preferendum!” for environmental variables) exclusively from field data 
has some bias. It may however represent a practical and valuable strategy to document species 
traits when other sources of information are lacking, in complement with bibliographic data 
already available on the biology and ecology of taxa. We assume that many ecological traits can 
be derived from characteristics of habitats. In contrast, the same approach may be problematic 
for biological traits (e.g. traits related to life history, behaviour, reproduction, nutrition…). 
Various approaches are thus clearly necessary. Despite these limitations, we believe that our 
approach and initial data set could contribute to identify ecological responses of invertebrate 
communities of tropical streams to natural and anthropic pertubations.  
References
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Tables and figure
Table 1. Habitat variables used to define the ecological traits (6 variables, 21 categories).
Table 2. Ecological traits for 32 neotropical taxa from the Yungas Bolivian rivers (matrix for 
21 categories of 6 traits). Affinity scale : 0 – “!no affinity!”!; 4 – “!high affinity!”.
Figure 1. Strategy to derive the affinity matrix per taxon for the 21 categories of the 6 
ecological traits. Illustration for Hydropsychidae and the 3rd ecological trait (dominating 
substrate) with 4 categories. 
Figure 2. Percentages of taxa with high affinities (code 3 to 5) with the considered parameter 
modality.
Fossati, Dumas et al. Tab. 1
Fossati, Dumas et al. Tab. 2
Fossati, Dumas et al. Fig. 1
Fossati, Dumas et al. Fig. 2
 


Deriving life traits from habitat characteristics : an initial application for neotropical invertebrates

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