, Volume 142, Issue 3, pp 353–359 | Cite as

Functional regularity: a neglected aspect of functional diversity

  • David MouillotEmail author
  • W. H. Norman Mason
  • Olivier Dumay
  • J. Bastow Wilson


Functional diversity has been identified as a key to understanding ecosystem and community functioning. However, due to the lack of a sound definition its nature and measurement are still poorly understood. In the same way that species diversity can be split into species richness and species evenness, so functional diversity can be split into functional richness (i.e. the amount of functional trait/character/attribute space filled) and functional evenness (i.e. the evenness of abundance distribution in functional trait space). We propose a functional regularity index (FRO) as a measure of functional evenness for situations where species are represented only by a single functional trait value (e.g. mean, median or mode), and species abundances are known. This new index is based on the Bulla O index of species evenness. When dealing with functional types or categorical functional traits, the Bulla O or any other accepted species evenness index may be used directly to measure functional evenness. The advantage of FRO is that it supplies a measure of functional evenness for continuous trait data. The FRO index presented in this paper fulfils all the a priori criteria required. We demonstrate with two example datasets that a range of FRO values may be obtained for both plant and animal communities. Moreover, FRO was strongly related to ecosystem function as seen in photosynthetic biomass in plant communities, and was able to differentiate sampling stations in a lagoon based on the functional traits of fish. Thus, the FRO index is potentially a highly useful tool for measuring functional diversity in a variety of ecological situations.


Brackish lagoon fishes Functional diversity Functional niche Functional traits Plant biomass 



We thank Pierre-Samuel Tari, Laurianne Laine, François Moreno and Jean-Antoine Tomasini for help in the sampling program and in the measure of functional traits. Two anonymous reviewers provided helpful comments. This work was supported by the grant 002420 from University of Montpellier II on ‘Functional diversity of lagoon fish species’.


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Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • David Mouillot
    • 1
    Email author
  • W. H. Norman Mason
    • 2
  • Olivier Dumay
    • 1
  • J. Bastow Wilson
    • 2
  1. 1.UMR CNRS-UMII 5119 Ecosystèmes LagunairesUniversité Montpellier II CC 093Montpellier Cedex 5France
  2. 2.Botany DepartmentUniversity of OtagoDunedinNew Zealand

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