Functional regularity index (FRO for single traits)

Overall functional regularity index (OFRO for multiple traits)

FRO measures functional evenness using a single functional trait weighting by species abundace. It indicates how evenly-spaced species are in functional space.

OFRO is a modification of FRO when functional regularity for more than one traits needs to be estimated.


David Mouillot, W. H. Norman Mason, Olivier Dumay, and J. Bastow Wilson

Published in

Oecologia 141, 2005, pp 353-359.


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To calcualte the index for multiple traits (OFRO) can be done either by calculating FRO separately for each trait, and taking the average of all these values, or by computing a principal components analysis and then using an eigenvalue to calcula FRO.

OFRO is not recommended with species richness is < 10.


This index uses the real values of functional traits continous scales such as leaf size, weighted by abundance.

Functional regularity can be estimated as well for categorical traits (e.g. types of dispersal) and for functional groups.

FRO is independent of species and functional richness.

Main characteristics

This index is based on Bulla´s (1994) especies evennes index. Abundance weighted index.

FRO is orthogonal (independent) of functional richness.

R Package/software

fDiversity software

R Package description

Studies that used this index


Bulla L (1994) An index of evenness measure. Oikos 70:167–171.


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