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Auteur (up) Carteron, A.; Jeanmougin, M.; Leprieur, F.; Spatharis, S. url  doi
openurl 
  Titre Assessing the efficiency of clustering algorithms and goodness-of-fit measures using phytoplankton field data Type Article scientifique
  Année 2012 Publication Revue Abrégée Ecol. Inform.  
  Volume 9 Numéro Pages 64-68  
  Mots-Clés 2-norm; Beta diversity; Cophenetic correlation coefficient; Dendrogram; Upgma; Ward's algorithm; beta-diversity; blooms; classification; communities; cophenetic correlation; environment; forest; functional diversity; som  
  Résumé Investigation of patterns in beta diversity has received increased attention over the last years particularly in light of new ecological theories such as the metapopulation paradigm and metacommunity theory. Traditionally, beta diversity patterns can be described by cluster analysis (i.e. dendrograms) that enables the classification of samples. Clustering algorithms define the structure of dendrograms, consequently assessing their performance is crucial. A common, although not always appropriate approach for assessing algorithm suitability is the cophenetic correlation coefficient c. Alternatively the 2-norm has been recently proposed as an increasingly informative method for evaluating the distortion engendered by clustering algorithms. In the present work, the 2-norm is applied for the first time on field data and is compared with the cophenetic correlation coefficient using a set of 105 pairwise combinations of 7 clustering methods (e.g. UPGMA) and 15 (dis)similarity/distance indices (e.g. Jaccard index). In contrast to the 2-norm, cophenetic correlation coefficient does not provide a clear indication on the efficiency of the clustering algorithms for all combinations. The two approaches were not always in agreement in the choice of the most faithful algorithm. Additionally, the 2-norm revealed that UPGMA is the most efficient clustering algorithm and Ward's the least. The present results suggest that goodness-of-fit measures such as the 2-norm should be applied prior to clustering analyses for reliable beta diversity measures. (C) 2012 Elsevier B.V. All rights reserved.  
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  Langue English Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 1574-9541 ISBN Médium  
  Région Expédition Conférence  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 457  
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Auteur (up) Maire, Eva; Grenouillet, G.; Brosse, S.; Villeger, S. url  doi
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  Titre How many dimensions are needed to accurately assess functional diversity? A pragmatic approach for assessing the quality of functional spaces Type Article scientifique
  Année 2015 Publication Revue Abrégée Global Ecology and Biogeography  
  Volume 24 Numéro 6 Pages 728-740  
  Mots-Clés Diversity indices; functional dendrogram; functional dissimilarity; functional ecology; functional traits; multidimensional space  
  Résumé Aim Functional diversity is a key facet of biodiversity that is increasingly being measured to quantify its changes following disturbance and to understand its effects on ecosystem functioning. Assessing the functional diversity of assemblages based on species traits requires the building of a functional space (dendrogram or multidimensional space) where indices will be computed. However, there is still no consensus on the best method for measuring the quality of functional spaces. Innovation Here we propose a framework for evaluating the quality of a functional space (i.e. the extent to which it is a faithful representation of the initial functional trait values). Using simulated datasets, we analysed the influence of the number and type of functional traits used and of the number of species studied on the identity and quality of the best functional space. We also tested whether the quality of the functional space affects functional diversity patterns in local assemblages, using simulated datasets and a real study case. Main conclusions The quality of functional space strongly varied between situations. Spaces having at least four dimensions had the highest quality, while functional dendrograms and two-dimensional functional spaces always had a low quality. Importantly, we showed that using a poor-quality functional space could led to a biased assessment of functional diversity and false ecological conclusions. Therefore, we advise a pragmatic approach consisting of computing all the possible functional spaces and selecting the most parsimonious one.  
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  Langue en Langue du Résumé Titre Original  
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  Volume de collection Numéro de collection Edition  
  ISSN 1466-8238 ISBN Médium  
  Région Expédition Conférence  
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  Numéro d'Appel MARBEC @ alain.herve @ collection 1341  
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Auteur (up) Villeger, S.; Maire, Eva; Leprieur, F. doi  openurl
  Titre On the risks of using dendrograms to measure functional diversity and multidimensional spaces to measure phylogenetic diversity: a comment on Sobral et al. (2016) Type Article scientifique
  Année 2017 Publication Revue Abrégée Ecol. Lett.  
  Volume 20 Numéro 4 Pages 554-557  
  Mots-Clés assemblages; cophenetic distance; dendrogram; Euclidean space; functional diversity; functional space; phylogenetic diversity; reveals  
  Résumé Sobral et al. (Ecology Letters, 19, 2016, 1091) reported that the loss of bird functional and phylogenetic diversity due to species extinctions was not compensated by exotic species introductions. Here, we demonstrate that the reported changes in biodiversity were underestimated because of methodological pitfalls.  
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  Langue English Langue du Résumé Titre Original  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 1461-023x ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ alain.herve @ collection 2116  
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