Use of invertebrate traits for the biomonitoring of European large rivers: the effects of sampling effort on genus richness and functional diversity

Abstract

1. Studies on biodiversity and ecosystem function require considering metrics for accurately describing the functional diversity of communities. The number of taxa (richness) is commonly used to characterise biological diversity. The disadvantage of richness as a measure of biological diversity is that all taxa are taken into account on an equal basis regardless of their abundance, their biological characteristics or their function in the ecosystem. 2. To circumvent this problem, we applied a recently described measure of biological diversity that incorporates dissimilarities among taxa. Dissimilarities were defined from biological traits (e.g. life history, morphology, physiology and behaviour) of stream invertebrate taxa and the resulting biological diversity index was considered as a surrogate for functional diversity. 3. As sampling effort is known to affect the number of taxa collected within a reach, we investigated how change in functional diversity is affected by sampling effort. We used stream invertebrate community data from three large European rivers to model accumulation curves and to assess the number of samples required to estimate (i.e. closeness to the maximal value) functional diversity and genera richness. We further evaluated the precision of estimates (i.e. similarity of temporal or spatial replicates) of the total functional diversity. 4. As expected, richness estimates were strongly dependent on sampling effort, and 10 replicate samples were found to underestimate actual richness. Moreover, richness estimates showed much variation with season and location. In contrast, functional diversity had greater accuracy with less sampling effort and the precision of the estimates was higher than richness both across sampling occasions and sampling reaches. These results are further arguments towards conducting research on the design of a biomonitoring tool based on biological traits.

On the challenge of treating various types of variables: application for improving the measurement of functional diversity

“…Let a imk be the affinity of species i for the level m of the kth variable, 1 5 m 5 M k . Fuzzy variables can be transformed into proportion variables via q imk 0 a imk =a m a imk (Chevenet et al 1994, Bady et al 2005. Let X k be a variable defined on…”

Can biological invertebrate traits resolve effects of multiple stressors on running water ecosystems?

“…To assess this topic, Bady et al (2005) compared a traditional diversity description (genus richness) with the functional diversity calculated using multiple biological traits and samples from three large European rivers. Genus richness depended strongly on sampling effort, season and sampling location within a given river.…”

Do different facets of littoral macroinvertebrate diversity show congruent patterns in a large lake system?

“…Advantages of using functional diversity measures include that they may allow rather straightforward comparison between studies based on different sets of species in different regions (e.g., Gallardo et al 2011). Functional diversity also has lower sensitivity to sampling effort than species diversity (e.g., Bady et al 2005), although a potential disadvantage is that functional diversity metrics are often redundant with species diversity metrics (e.g., Gallardo et al 2011). Finally, taxonomic distinctness indices have commonly been used in the assessment of environmental pollution in marine environments (Warwick and Clarke 1995, Leonard et al 2006, and an increasing trend is to apply them to address similar problems in freshwater ecosystems (Abellán et al 2006, Leira et al 2009).…”