#### The simplest and most common way to measure biodiversity is to measure species richness: count the number of species present in the habitat.  The more species are present, the higher the biodiversity!  However, species richness does not always capture everything about biodiversity.  Consider the two communities illustrated below:

In your opinion, which of these communities looks more diverse?

Each of the communities has a species richness of three (silversides, cunners, and pipefish), but they are clearly not the same!  Community 1 has an even mix of species, but Community 2 is almost entirely made up of silversides.  Scientists have developed some alternative measures of biodiversity that we can use in this situation, that take into account both species richness AND the distribution of those species.

The biodiversity measure we will use today is one of the most common measures used by scientists, known as the Shannon Index.  The formula for the Shannon index is included below - you may use this formula to calculate it, or you may use an online calculator (see link below in the data section).  The higher the Shannon Index, the higher the biodiversity.

Calculating the Shannon Index​ (Optional):

H’ is the Shannon Index, and p  is the proportion of all the organisms captured that are from that particular species. For example, if you captured 12 organisms, and two of them were shrimp, p   for shrimp would be 2/12 = 0.17

To calculate the Shannon index, first calculate p  for each species in your dataset.  Next, multiply each p   by the natural log (ln) of that same p  ,  add them all up, and then multiply by negative one.

i

i

i

i

i

#### ​

1. First, calculate the species richness simply by counting the number of different types of organisms captured at each location.  Record these numbers in a table on your sheet of paper.

2. Second, calculate the Shannon Index.  If you have sufficient math background you can do this yourself using the formula in the section above, or you can use this online calculator.  Remember, the higher the Shannon Index, the higher the biodiversity.  When using the online calculator, follow these directions:

1. Enter the species richness in the box for “number of species/taxa in sample’ and hit ‘submit’

2. Enter the numbers of each taxa in the red-outlined boxes.  It is not necessary to type in the names of the species. You should enter a number for each box (no zeroes) and hit ‘submit’

3. The output includes a TON of diversity measures.  There are three entries for the Shannon Index; you want the one that matches the formula above (the middle one in the left hand column).

4. Record the Shannon Index in a table on your piece of paper.

Next, illustrate the data by making two graphs - one for species richness, and one for Shannon Index.  Your graphs should have clear labels on both the x-axis and the y-axis.  The type of graph (scatterplot, column graph, etc) is up to you.