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Vol. 51 No. 4, 2012
Taxonomic Relatedness of Spider and Carabid Assemblages in a
Wetland Ecosystem
Mauro
Paschetta1,*, PierMauro Giachino2, and Marco Isaia1
1Dipartimento
di Biologia Animale e dell’Uomo, 13 Via Accademia Albertina, Turin
10123, Italy
2Environment Park, Settore Fitosanitario Regionale, 60
Via Livorno, Turin 10144, Italy
Mauro Paschetta, PierMauro Giachino, and
Marco Isaia (2012) Traditional community indices, i.e. Shannon
diversity and Simpson’s dominance, are generally used to describe
biological assemblages in order to infer ecological trends about the
effects of disturbance. Such indices are correlated with species
richness and abundance and may be strongly influenced by the sampling
effort. Conversely, taxonomic relatedness indices show
interesting statistical properties and are independent of the sampling
effort. Additionally, high values of taxonomical relatedness
indices have proven to reflect habitat functionality in marine
ecosystems. Their use in terrestrial ecosystems is rare, and
despite their good potential, they have never been used for
biodiagnostic purposes. In this paper, we present the 1st
application of taxonomic relatedness indices to arthropod assemblages
(namely spiders and carabids) and their comparison with several
traditional community parameters that are generally used to evaluate
environmental disturbances. The study was set in a wetland area
within the Natural Reserve of Fondo Toce (northwestern Italy).
Four different habitats with different degrees of disturbance (a reed
bed, a mown meadow, a riparian wood with mesophilous elements, and a
transitional mesohygrophilic area invaded by non-native vegetation)
were sampled using pitfall traps. The spider and carabid
assemblages occurring in each habitat were characterized by means of
multidimensional scaling (MDS) and by several community parameters,
including abundance, species richness diversity, taxonomic relatedness
indices, and some descriptive functional traits. Differences
among habitats were tested with generalized linear models.
Correlations among community parameters were evaluated with Spearman’s
rank correlations. According to the MDS plots, both assemblages
were clearly separated in relation to habitat type. When
considering the parameters describing the assemblages in relation to
disturbance, the taxonomic approach was found to be particularly
suitable for spiders, for which the less-disturbed habitat was
characterized by higher values of average taxonomic distinctness.
Furthermore, functional groups of spiders were more evenly distributed
in undisturbed habitats. The functional approach was found
particularly appropriate for carabids, which responded to disturbance
in terms of a decrease in biomass (average body size) and an increase
in the proportional abundance of macropterous individuals.
Key words: Ecology, Taxonomic distinctness,
Diversity, Functional traits, Habitat disturbance.
*Correspondence: Tel: 39-0116704544.
E-mail:mauro.paschetta@gmail.com
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