Legras G. auteur aut IRD Loiseau N. auteur aut IRD Gaertner Jean-Claude auteur aut IRD Poggiale J.C. auteur aut IRD Gaertner-Mazouni N. auteur aut IRD text journalArticle eng text/pdf born digital access The impact of the variation of the number of functional traits on functional diversity assessment is still poorly known. Although the covariation between these two parameters may be desirable in some situations (e.g. if adding functional traits provides relevant new functional information), it may also result from mathematical artefacts and lead to misinterpretation of the results obtained. Here, we have tested the behaviour of a set of nine indices widely used for assessing the three main components of functional diversity (i.e. functional richness, evenness and divergence), according to the variation in the number of functional traits. We found that the number of functional traits may strongly impact the values of most of the indices considered, whatever the functional information they contain. The FRic, TOP and n-hypervolume indices that have been developed to characterize the functional richness component appeared to be highly sensitive to the variation in the number of traits considered. Regarding functional divergence, most of the indices considered (i.e. Q, FDis and FSpe) also showed a high degree of sensitivity to the number of traits considered. In contrast, we found that indices used to compute functional evenness (FEve and Ru), as well as one of the indices related to functional divergence (FDiv), are weakly influenced by the variation in the number of traits. All these results suggest that interpretation of most of the functional diversity indices considered cannot only be based on their values as they are, but requires taking into account the way in which they have been computed specialized MONDE 040INFSTA 020MATH01 021ENVECO 13 1 117-126 2019 1874-1738 https://www.documentation.ird.fr/hor/fdi:010080802 10.1007/s12080-019-00433-x 1874-1738 [F B010080802] https://www.documentation.ird.fr/hor/fdi:010080802 https://www.documentation.ird.fr/intranet/publi/2021-07/010080802.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2021-04-20 2025-02-24 fdi:010080802 fre