## Diversity index: Simpson’s Index (D)

Simpson diversity index is another diversity measure that takes into account the number of species and their abundance in a community. It is calculated as the proporotion (*p _{i}*) of species

*i*to the total number of species , that is squared and summed for all the species and the reciprocal is taken. It has also been defined as the probability the two individual taken from the same sample will belong to same species.

1

D=_____

∑ (P_{i} ^2)

The value of D ranges between 0 and 1, with 0 being infinite diversity and 1 being no diversity. This is not quite intuitive with lower number indicating higher diversity, so in these cases **Simpson’s Index of Diversity** (1 – **D) **is preferred, which makes more sense in terms of number as higher number donating higher diversity. In this case, (1-D) is defined as a probability the two individual taken from a sample will belong to two different species.

**Source:**

http://www.countrysideinfo.co.uk/simpsons.htm

http://www.tiem.utk.edu/~gross/bioed/bealsmodules/simpsonDI.html