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Associations between species and groups of sites : indices and statistical inference / Miquel De Caceres in Ecology, vol. 90, n°12 (Année 2009)  

Public [article]  inEcology > vol. 90, n°12 (Année 2009) . - pp. 3566-3574 Titre : Associations between species and groups of sites : indices and statistical inference Type de document : texte imprimé Auteurs : Miquel De Caceres, Auteur ; Pierre Legendre, Auteur Année de publication : 2009 Article en page(s) : pp. 3566-3574 Langues : Anglais (eng) Mots-clés : community types  fidelity measure  indicator value  phi coefficient of association Résumé : "Ecologists often face the task of studying the association between single speciesand one or several groups of sites representing habitat types, community types, or othercategories. Besides characterizing the ecological preference of the species, the strength of theassociation usually presents a lot of interest for conservation biology, landscape mapping andmanagement, and natural reserve design, among other applications. The indices mostfrequently employed to assess these relationships are the phi coefficient of association and theindicator value index (IndVal). We compare these two approaches by putting them into abroader framework of related measures, which includes several new indices. We presentpermutation tests to assess the statistical significance of species–site group associations andbootstrap methods for obtaining confidence intervals. Correlation measures, such as the phicoefficient, are more context-dependent than indicator values but allow focusing on thepreference of the species. In contrast, the two components of an indicator value index directlyassess the value of the species as a bioindicator because they can be interpreted as its positivepredictive value and sensitivity. Ecologists should select the most appropriate index ofassociation strength according to their objective and then compute confidence intervals todetermine the precision of the estimate." Type de publication : périodique Référence biblio : De Caceres M., Legendre P., 2009 - Associations between species and groups of sites : indices and statistical inference. Ecology, 90 (12) : 3566-3574. En ligne : http://adn.biol.umontreal.ca/~numericalecology/Reprints/De_Caceres_&_Legendre_Ec [...] Format de la ressource électronique : document Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=66166 [article]

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Species Assemblages and Indicator Species : The Need for a Flexible Asymmetrical Approach / Marc Dufrêne in Ecological monographs, vol. 67, n°3 (Année 1997)

Public [article]  inEcological monographs > vol. 67, n°3 (Année 1997) . - pp. 345-366 Titre : Species Assemblages and Indicator Species : The Need for a Flexible Asymmetrical Approach Type de document : texte imprimé Auteurs : Marc Dufrêne, Auteur ; Pierre Legendre, Auteur Année de publication : 1997 Article en page(s) : pp. 345-366 Langues : Anglais (eng) Catégories : [ZG] Belgique [Thèmes] Outils et méthodes Mots-clés : Carabe  espèce eurytopique  espèce indicatrice  analyse multivariée Résumé : "This paper presents a new and simple method to find indicator species and species assemblages characterizing groups of sites. The novelty of our approach lies in the way we combine a species relative abundance with its relative frequency of occurrence in the various groups of sites. This index is maximum when all individuals of a species are found in a single group of sites and when the species occurs in all sites of that group; it is a symmetric indicator. The statistical significance of the species indicator values is evaluated using a randomization procedure. Contrary to TWINSPAN, our indicator index for a given species is independent of the other species relative abundances, and there is no need to use pseudospecies. The new method identifies indicator species for typologies of species releves obtained by any hierarchical or nonhierarchical classification procedure; its use is independent of the classification method. Because indicator species give ecological meaning to groups of sites, this method provides criteria to compare typologies, to identify where to stop dividing clusters into subsets, and to point out the main levels in a hierarchical classification of sites. Species can be grouped on the basis of their indicator values for each clustering level, the heterogeneous nature of species assemblages observed in any one site being well preserved. Such assemblages are usually a mixture of eurytopic (higher level) and stenotopic species (characteristic of lower level clusters). The species assemblage approach demonstrates the importance of the "sampled patch size," i.e., the diversity of sampled ecological combinations, when we compare the frequencies of core and satellite species. A new way to present species-site tables, accounting for the hierarchical relationships among species, is proposed. A large data set of carabid beetle distributions in open habitats of Belgium is used as a case study to illustrate the new method.' Type de publication : périodique Référence biblio : Dufrêne M., Legendre P., 1997 - Species Assemblages and Indicator Species : The Need for a Flexible Asymmetrical Approach. Ecological monographs, 67 (3) : 345-366. ID PMB : 71033 DOI : 10.2307/2963459 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=71033 [article]

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