A critique of the use of indicator-species scores for identifying thresholds in species responses

Cuffney, Thomas F.; Qian, Song S.

doi:10.1899/12-056.1

Cited by 12 publications

(10 citation statements)

References 39 publications

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“…While some have pointed out the limitations of TITAN2 (Cuffney & Qian, ; Cuffney, Qian, Brightbill, May, & Waite, ), including its limited ability to detect thresholds in models with abrupt changes in response slopes or direction (Cuffney & Qian, ), we contend that the ability of TITAN2 to identify velocity thresholds is appropriate because taxa or trait responses to natural flow gradients are likely to be more gradual than responses for other types of disturbance. The use of TITAN2 is particularly appropriate for our study because we used only samples taken from reference and potential reference sites, meaning that taxa and trait responses were unlikely to follow a dose–response distribution, which is where TITAN2 did not perform well (Cuffney & Qian, ). Our findings that TITAN2 identified many EPT taxa as positively responding flow point thresholds (Figure a) support the notion that TITAN2 is able to identify and substantiate taxonomic change points across flow gradients.…”

Section: Discussionmentioning

confidence: 94%

“…increasing mining and hydropower developments in the North) (Cherry et al, 2017;Shrubsole, Walters, Veale, & Mitchell, 2016). Therefore, there is a need to shift towards new approaches for integrated water resource management that synthesise the available scientific information into ecologically based and socially acceptable flow targets for environmental management (Poff, Richter, et al, 2010;Richter, 2010 (Cuffney & Qian, 2013), we contend that the ability of TITAN2 to identify velocity thresholds is appropriate because taxa or trait responses to natural flow gradients are likely to be more gradual than responses for other types of disturbance. The use of TITAN2 is particularly appropriate for our study because we used only samples taken from reference and potential reference sites, meaning that taxa and trait responses were unlikely to follow a dose-response distribution, which is where TITAN2 did not perform well (Cuffney & Qian, 2013).…”

Section: Ecological Implications Of a Traits-based Approach To Idenmentioning

confidence: 99%

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Flow velocity–ecology thresholds in Canadian rivers: A comparison of trait and taxonomy‐based approaches

Monk

Compson

Armanini³

et al. 2017

Freshwater Biology

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Understanding the physical and biological mechanisms contributing to flow velocity–ecology relationships is crucial for successful river management. The application of an ecological traits‐based approach offers the potential to explore mechanistic linkages between aquatic communities and a hydrological gradient. To date, however, studies focused on identifying these relationships have been limited by a lack of large‐scale, long‐term biological data. To address this gap at a scale relevant for water policy management, we employed data from a large‐scale standardised benthic monitoring program—the Canadian Aquatic Biomonitoring Network—obtained from wadeable river sites across Canada. We applied the Threshold Indicator Taxa ANalysis method to quantify the response of the macroinvertebrate community, expressed as traditional taxonomic information and also as ecological traits, along a flow velocity gradient in reference and potential reference sites. Five key findings emerged: (1) using taxa and trait modalities revealed different flow velocity thresholds, (2) trait flow velocity indicators were less variable than taxon indicators, especially for positively responding trait modalities, (3) labile and non‐labile trait modalities demonstrated highly similar patterns along the flow velocity gradient, (4) taxa from 12 different orders responded negatively to flow velocity, while only EPT taxa and some dipterans responded positively to flow velocity, and (5) traits related to mobility and ecology (e.g. climber and swimmer habits, preference of cold‐cool eurythermal water and ability to survive desiccation) tended to respond positively to flow velocity, while traits related to morphology, life history and ecology (e.g. sprawler and burrower habits, preference for warm eurythermal water and inability to survive desiccation) tended to respond negatively to flow velocity. Providing ecologically based flow management targets can improve management plans, anticipate ecosystem consequences of anthropogenic change and support the development of policies to mitigate anthropogenic flow alteration. While our taxon and trait modality flow indicators were developed for Canadian watersheds, our methods to develop flow indicators and thresholds are transferrable to other systems where long‐term biomonitoring programs are being developed, underscoring the need for long‐term biomonitoring programs to support better ecosystem management.

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Section: Discussionmentioning

confidence: 94%

Section: Ecological Implications Of a Traits-based Approach To Idenmentioning

confidence: 99%

Flow velocity–ecology thresholds in Canadian rivers: A comparison of trait and taxonomy‐based approaches

Monk

Compson

Armanini³

et al. 2017

Freshwater Biology

View full text Add to dashboard Cite

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“…Another limit of the deviance reduction approach is its sensitivity to the distribution of data in the gradient. It was numerically demonstrated that such an analysis do not find the same thresholds whether sampling is uniform or not (Cuffney and Qian 2013;Daily et al 2012). In gradient forest, the use of the ratio of split-over-data densities adjusts for the bias created by data skewness and leads to a better identification of ecological thresholds (e.g.…”

Section: Statistical Approachmentioning

confidence: 99%

“…The changes in abundance due to limits in the biogeographic extension area of species, may interfere in the search for environmental thresholds (false zeros) when analysis is conducted at species level and at large spatial scale (Cuffney and Qian 2013;Utz et al 2009). Aggregating species into metrics or higher taxonomic levels decreases spatial dependency but implies a loss of information.…”

Section: Statistical Approachmentioning

confidence: 99%

Identification of ecological thresholds from variations in phytoplankton communities among lakes: contribution to the definition of environmental standards

Roubeix¹,

Danis

Feret

et al. 2016

Environ Monit Assess

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In aquatic ecosystems, the identification of ecological thresholds may be useful for managers as it can help to diagnose ecosystem health and to identify key levers to enable the success of preservation and restoration measures. A recent statistical method, gradient forest, based on random forests, was used to detect thresholds of phytoplankton community change in lakes along different environmental gradients. It performs exploratory analyses of multivariate biological and environmental data to estimate the location and importance of community thresholds along gradients. The method was applied to a data set of 224 French lakes which were characterized by 29 environmental variables and the mean abundances of 196 phytoplankton species. Results showed the high importance of geographic variables for the prediction of species abundances at the scale of the study. A second analysis was performed on a subset of lakes defined by geographic thresholds and presenting a higher biological homogeneity. Community thresholds were identified for the most important physico-chemical variables including water transparency, total phosphorus, ammonia, nitrates, and dissolved organic carbon. Gradient forest appeared as a powerful method at a first exploratory step, to detect ecological thresholds at large spatial scale. The thresholds that were identified here must be reinforced by the separate analysis of other aquatic communities and may be used then to set protective environmental standards after consideration of natural variability among lakes.

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“…For example, in a series of simulations, Ficetola and Denoël (2009) tested whether logistic regression could identify a breakpoint-based threshold even though standard logistic regression can only be used to identify classification thresholds. Similarly, Baker and King (2010) implied that their approach could identify breakpoint-based thresholds, and was therefore tested for its ability to do so by Cuffney and Qian (2013), although it actually identifies a community-level analogue of a classification threshold. The two types of thresholds will tend to differ in location because they must be identified using different statistical methods.…”

Section: Introductionmentioning

confidence: 99%

Threshold detection: matching statistical methodology to ecological questions and conservation planning objectives

Toms¹,

Villard²

2015

ACE

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ABSTRACT. Two types of ecological thresholds are now being widely used to develop conservation targets: breakpoint-based thresholds represent tipping points where system properties change dramatically, whereas classification thresholds identify groups of data points with contrasting properties. Both breakpoint-based and classification thresholds are useful tools in evidence-based conservation. However, it is critical that the type of threshold to be estimated corresponds with the question of interest and that appropriate statistical procedures are used to determine its location. On the basis of their statistical properties, we recommend using piecewise regression methods to identify breakpoint-based thresholds and discriminant analysis or classification and regression trees to identify classification thresholds. Détection des seuils : choix de la méthode statistique en fonction des questions écologiques et des objectifs de planification de la conservationRÉSUMÉ. À l'heure actuelle, deux types de seuils écologiques sont communément utilisés dans l'élaboration d'objectifs de conservation : alors que les seuils correspondant à un point de rupture représentent le point de basculement où les propriétés du système changent radicalement, les seuils de classification, eux, séparent les données en groupes ayant des propriétés divergentes. Tant les seuils fondés sur le point de rupture que ceux fondés sur la classification sont des outils utiles pour la conservation issue d'observations. Toutefois, le type de seuils que nous cherchons à estimer doit impérativement concorder avec la question qui nous préoccupe, tandis que la méthode statistique utilisée pour déterminer la localisation précise du seuil doit être appropriée. En nous fondant sur leurs propriétés statistiques, nous recommandons l'utilisation d'une méthode de régression par segments pour déterminer un seuil correspondant à un point de rupture et d'une analyse discriminante ou d'un arbre de classification ou de régression pour déterminer un seuil de classification.

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A critique of the use of indicator-species scores for identifying thresholds in species responses

Cited by 12 publications

References 39 publications

Flow velocity–ecology thresholds in Canadian rivers: A comparison of trait and taxonomy‐based approaches

Flow velocity–ecology thresholds in Canadian rivers: A comparison of trait and taxonomy‐based approaches

Identification of ecological thresholds from variations in phytoplankton communities among lakes: contribution to the definition of environmental standards

Threshold detection: matching statistical methodology to ecological questions and conservation planning objectives

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