How do we measure diversity?

EESC04

Afternoon Lab

What are the common ways of measuring diversity?

• Richness: # of species

• Relative abundance: proportion of a species in a community

• Evenness: how well represented is a species?

Scale matters: Diversity at different levels

• α-diversity – local diversity (single site) – Species Richness

– Shannon-Wiener Index

– Simpson Index

• β-diversity – change in diversity between sites – Sorensen Index (also known as Bray-Curtis)

– Jaccard Index

• γ-diversity – regional diversity

• ε-diversity if we are looking at a larger scale

Which site has the highest alpha-diversity?

Site A Site B

Site C Site D

Region X Region Y

Which site has the highest alpha-diversity?

Site A Site B

Site C Site D

Region X Region Y

Which region has the highest beta-diversity?

Site A Site B

Site C Site D

Region X Region Y

Which region has the highest beta-diversity?

Site A Site B

Site C Site D

Region X Region Y

Which region has the highest gamma-diversity?

Site A Site B

Site C Site D

Region X Region Y

Which region has the highest gamma-diversity?

Site A Site B

Site C Site D

Region X Region Y

Some useful indices

• Shannon-Wiener Index

• Shannon Evenness

• Simpson Index

• Margalef Index

• Berger-Parker Index

Shannon-Wiener Index

• 𝐻′ = − 𝑝𝑖 ln 𝑝𝑖𝑆𝑖=1

• pi = relative frequency of species

# 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑠𝑝𝑒𝑐𝑖𝑒𝑠

𝑡𝑜𝑡𝑎𝑙 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠

• Values range from 0 – 5

– Usually between 1.5 and 3.5

• Sensitive to sampling bias

Shannon Evenness

• 𝐸𝐻 =𝐻′

𝐻𝑚𝑎𝑥

• 𝐻𝑚𝑎𝑥 = ln 𝑆, where S = species richness

– ie: 𝐸𝐻 =𝐻′

ln 𝑆

• E ranges from 0 – 1 (1 is most even)

Simpson Index

• 𝐷 = 𝑛𝑖 𝑛𝑖−1

𝑁(𝑁−1)

𝑆𝑖=1

• ni = # of individuals of each species

• N = total individuals

• Less sensitive to species richness and weighs more abundant species more

• Less sensitive than Shannon-Wiener

Margalef and Berger-Parker

• Margalef:

– 𝐷𝑀𝐺 =𝑆−1

ln 𝑁

– Accounts for biases in sampling size and effort

– S = species richness

– N = total # of individuals

• Berger-Parker:

– 𝐷𝐵𝑃 =𝑁𝑚𝑎𝑥

𝑁

– Looks at how important the most abundance species is

– Nmax = # of individuals from most abundant species

– Not very informative as it just looks at one species

Jaccard and Sorensen

• Jaccard:

– 𝑆𝐽 =𝑎

𝑎+𝑏+𝑐

– a = # of species found in all sites

– b = # of species found in site 1

– c = # of species found in site 2

• Sorensen:

– 𝑆𝑆 =2𝑎

2𝑎+𝑏+𝑐

– a = # of species found in all sites

– b = # of species found in sites 1

– c = # of species found in sites 2

• Comparison between 2 sites • Can’t use these for our data

Taken from Lecture 2, EESC04, September 9, 2014

Taken from Lecture 2, EESC04, September 9, 2014

Taken from Lecture 2, EESC04, September 9, 2014

Taken from Lecture 2, EESC04, September 9, 2014

How can we conceptualize diversity?

• Genetic diversity

• Functional diversity

• Ecosystem diversity

• Phylogenetic diversity

• Taxonomic diversity

Questions??