# Indicator value

Indicator value is a term that has been used in ecology for two different indices. The older usage of the term refers to Ellenberg's indicator values, which are based on a simple ordinal classification of plants according to the position of their realized ecological niche along an environmental gradient.[1] More recently, the term has also been used to refer to Dufrêne & Legendre's indicator value, which is a quantitative index that measures the statistical alliance of a species to any one of the classes in a classification of sites.[2]

## Ellenberg's Indicator Value

Ellenberg's indicator values[1] were the first model of bioindication proposed and applied to the flora of Germany, and they have a long tradition in interpretation and understanding of plant communities and their evolution. The latest edition of Ellenberg's indicator values applies a 9-point scale for each of six gradients: soil acidity, soil productivity or fertility, soil humidity, soil salinity, climatic continentality and light availability.[3] Indicator values also exist in Landolt's Flora of Switzerland[4] and some other floras. A substantial advance on a comparable scale to place a local flora on gradients are the climatic profiles of the French SOPHY online database.[citation needed]

## Indicator Value of Dufrêne and Legendre

This indicator value is an integral part of the indicator value , which quantifies the fidelity and specificity of species in relation to groups of sites in a user-specified classification of sites, and tests for the statistical significance of the associations by permutation.[2][5][6]

The indicator value of species i for class j is obtained with the equation

${\displaystyle IndVal_{ij}=A_{ij}*B_{ij}*100}$

Here

Aij is specificity, i.e. the proportion of the individuals of species i that are in class j
Bij is fidelity, i.e. the proportion of sites in class j that contain species i

## References

1. ^ a b Ellenberg H. Zeigerwerte der Gefässpflanzen Mitteleuropas / H. Ellenberg // Scripta geobotanica. Göttingen, 1974. – Vol. 9. – 197 p.
2. ^ a b Dufrene, M., and P. Legendre. 1997. Species assemblages and indicator species: The need for a flexible asymmetrical approach. Ecological Monographs 67:345-366.
3. ^ Ellenberg H., Weber H.E., Dull R., Wirth V., Werner W., Paulisen D. Zeigerwerte von Pflanzen in Mitteleuropa [Indicator values of plants in Central Europe] / H. Ellenberg, H.E. Weber, R. Dull, V. Wirth, W. Werner, D. Paulisen // Scripta Geobotanics. – V. 18. – Verlag Erich Goltze KG, Göttingen, 1991. – 248 s.
4. ^ Landolt E. Okologische Zeigerwerts zur Schweizer Flora / E. Landolt // Veroff. Geobot. Inst. ETH. Zurich. – 1977. – H. 64. – S. 1-208.
5. ^ De Caceres, M., and P. Legendre. 2009. Associations between species and groups of sites: indices and statistical inference. Ecology 90:3566-3574.
6. ^ De Caceres, M., P. Legendre, and M. Moretti. 2010. Improving indicator species analysis by combining groups of sites. Oikos 119:1674-1684.