On the Myths of Indicator Species: Issues and Further Consideration in the Use of Static Concepts for Ecological Applications

Abstract

The use of static indicator species, in which species are expected to have a similar sensitivity or tolerance to either natural or human-induced stressors, does not account for possible shifts in tolerance along natural environmental gradients and between biogeographic regions. Their indicative value may therefore be considered at least questionable. In this paper we demonstrate how species responses (i.e. abundance) to changes in sediment grain size and organic matter (OM) alter along a salinity gradient and conclude with a plea for prudency when interpreting static indicator-based quality indices. Six model species (three polychaetes, one amphipod and two bivalves) from the North Sea, Baltic Sea and the Mediterranean Sea region were selected. Our study demonstrated that there were no generic relationships between environment and biota and half of the studied species showed different responses in different seas. Consequently, the following points have to be carefully considered when applying static indicator-based quality indices: (1) species tolerances and preferences may change along environmental gradients and between different biogeographic regions, (2) as environment modifies species autecology, there is a need to adjust indicator species lists along major environmental gradients and (3) there is a risk of including sibling or cryptic species in calculating the index value of a species.

Global meta-analysis reveals low consistency of biodiversity congruence relationships

“…Further, SAIs differ from correlations in species richness or composition in that their values differ depending on which taxon is the target and which is the surrogate (that is, SAIs give two values for each pair of taxa, in contrast to correlations which give a single value for each pair). We found only six articles (and 104 observations) that used the SAI for assessing the degree of complementarity between taxa, possibly because there are many methods for assessing congruence in the complementarity literature 29 . Although six articles was too few to make broad comparisons regarding the influence of study design or location on observed levels of congruence, we were able to make some broad observations.…”

“…This can be achieved either by comparing species composition between taxa using Mantel tests 23,24 or by calculating the degree of overlap between optimal subsets of sites for each taxon 25,26 (an approach based on the principle of complementarity 27 ). Although these developments have been valuable, they present a challenge to those attempting to synthesize global knowledge on cross-taxon congruence because of the array of different methods that have been applied in the literature 28,29 . Therefore, despite the publication of a number of valuable reviews of the congruence literature 15,28,[30][31][32][33][34] , one important theme has yet to be addressed; namely, the observation that congruence is often highly variable when measured in different locations or at different times 29,35,36 .…”

“…Although these developments have been valuable, they present a challenge to those attempting to synthesize global knowledge on cross-taxon congruence because of the array of different methods that have been applied in the literature 28,29 . Therefore, despite the publication of a number of valuable reviews of the congruence literature 15,28,[30][31][32][33][34] , one important theme has yet to be addressed; namely, the observation that congruence is often highly variable when measured in different locations or at different times 29,35,36 . A key property of biodiversity surrogates and indicators is that they should be able to be applied with confidence in novel contexts 37 , and so this lack of consistency has the potential to undermine the usefulness of biodiversity surrogates in ecology and conservation 38 .…”

Polychaete/amphipod ratios: An approach to validating simple benthic indicators

“…a given species was included in a single ecological group) (Borja et al, 2000(Borja et al, , 2011. Others suggested that it is possible to observe different responses of species to organic matter, stress and pollution according to local and regional particularities (Grémare et al, 2009;Zettler et al, 2013). This could correspond to the existence of distinct adapted populations that can respond differently to pollution and, therefore, and be classified in several ecological groups in function to their sensitivity (Grémare et al, 2009;Zettler et al, 2013).…”

Predicting the Composition of Polychaete Assemblages in the Aegean Coast of Turkey

“…Frontiers in Marine Science | www.frontiersin.orgclassification database as opposed to a more widely used one (e.g., the AMBI classification database) was driven by findings that species can shift their tolerances between biogeographic regions with different dominant environmental gradients (Zettler et al, 2013) and the need to adjust species classification to ecological groups identified for the Aegean by Simboura and Reizopoulou (2007) and Çinar et al (2012).…”