An ecologist investigated the plant community in a coastal sand dune ecosystem. Table 1 shows the number of individuals of each plant species recorded within a sample plot.
Table 1
| Species | Number of individuals (nnn) |
|---|---|
| Ammophila arenaria | 12 |
| Eryngium maritimum | 4 |
| Festuca rubra | 18 |
| Lotus corniculatus | 8 |
| Trifolium repens | 15 |
| Plantago lanceolata | 7 |
Calculate the index of diversity (ddd) for this site using the formula:
d=N(N−1)∑n(n−1) d = \frac{N(N-1)}{\sum n(n-1)} d=∑n(n−1)N(N−1)Show your working and give your answer to 2 decimal places.