Measuring Biodiversity You need to know: What we mean by ‘biodiversity’ How to estimate biodiversity

Biodiversity Species richness Species evenness Number of different species in the habitat Qualitative measurement Relative abundance of individual species Quantitative measurement

Measuring species richness =Quantitative. Count the number of different species. Can use random quadrat technique No need to identify the species NB this measurement means that 1 daisy is worth as much as 100 buttercups…..so…

Measuring species evenness = Quantitative Plants – use random quadrats , count the number of each species or % cover. Calculate RELATIVE abundance.

Species evenness - Animals Count individuals or use mark and recapture method. Mark individuals and release. = C1 After period of time catch new sample = C2 Count number of marked individuals = C3 Catch a sample of animals eg using sweep net Calculate total population = (C1 x C2) C3

Worked example:- Two different fields were sampled for wildflowers Numbers of individuals Species Sample 1 Sample 2 Daisy 300 20 Dandelion 335 49 Buttercup 365 931 Total 1000 1000 Which field do you think is the most biodiverse, and why?

A community dominated by one or two species is considered to be less diverse than one in which several different species have a similar abundance. As species richness and evenness increase, so diversity increases. Simpson's Diversity Index is a measure of diversity which takes into account both richness and evenness.

Simpsons diversity index D = 1 - [ Σ(n / N)2 ] D = diversity of habitat Σ = sum of n = the total number of organisms of a particular species or percentage cover N = the total number of organisms of all species or % cover Using 1- means that as D increases so does the diversity.

Species n n/N (n/N)² Daisy Dandelion Buttercup Sum Σ 1 - Σ Work out the Simpsons Diversity index for the 2 fields. Numbers of individuals Species Sample 1 Sample 2 Daisy 300 20 Dandelion 335 49 Buttercup 365 931 Total 1000 1000 Species n n/N (n/N)² Daisy Dandelion Buttercup Sum Σ 1 - Σ

Now try this example on your own. Species n n/N (n/N)² Woodrush 2 Holly 8 Bramble 1 Yorkshire fog Sedge 3

Ans. Simpsons index of diversity for this area = 0.7 The results that you have just used were collected from 1 quadrat. Is this a reliable indication of the diversity of the habitat? Explain your answer.