Biodiversity Indices Lab Flashcards
What can be measured under the topic of biodiversity?
- Species Richness
- Abundance
- Diversity
Define “diversity”
Diversity is the relationship between richness and abundance
Biodiversity indices use both…?
Richness and abundance
How do biodiversity indices work?
They differ in mathematical methods by giving greater prominence to either richness or abundance.
Define “species richness (S)”
- Species richness is the total no. of species identified (incidence/presence data) per unit area.
- It is the simplest descriptor of community structure.
Can species richness (S) be used as independent information?
No, alone it is largely uninformative.
How is species richness used to assess diversity?
- It uses indices that incorporate information on abundance.
- It controls the effects of sample size (the no. of species is dependent on the samples size).
What is the formula for “Menhinick’s Index”?
D = S/ √ N
What values do S and N represent in Menhinick’s Index?
S = No. of different species in the sample
N = Total no. of individuals in the sample
Menhinick’s Index tried to account for the sample size but is strongly influenced by…?
The sampling effort
Dominance indices are measured using the…?
Simpson’s Diversity Index (D) (1/D)
Information indices are measured using the…?
Shannon-Weiner Index (H’)
Dominance indices are…?
Weighted towards abundant and common species (there are a few rare species that will not affect the diversity).
Information indices…?
- Can take into account rare species in a community
- Assume all species are represented in a sample and are sampled randomly
What does Simpson’s diversity (1/D) measure?
It measures the probability of any two individuals being conspecifics if randomly drawn from an infinitely large community.
Using Simpson’s Index, index increases with…?
Diversity
What is Shannon-Weiner (H’) to measure?
Used for t-tests and ANOVAs to compare sites (providing they meet the assumptions of the tests eg. normality etc).
What values does the Shannon-Weiner Index (H’) usually provide?
It usually provides values between 1.5 - 3.5
What is Everness (sample) measure (E)/ Piou’s (community) everness (J)?
It compares actual diversity values to the maximum diversity while assuming all species are present within the sample.
What is the equation for “Everness”?
Everness = H’/H’ max =H’/LnS
What equation values do H’ , H’ max and S represent?
H’ = Shannon-Weiner Index
H’ max = Maximum diversity which could occur if all species were equally abundant
S = Total no. of species
What do the equation values E/J and J represent?
E/J = constrained between 0-0.1
J = The less variation in communities between species the higher the value
What are the Community index of Similarities based on?
They are presence-absence based
i.e. species richness based
How is the Community index of similarities measured?
It’s measured using Sorensen’s Coefficient (CC)
What is the equation for Sorensen’s Coefficient (CC)?
CC = 2C/S1+S2
What do the values C, S1 and S2 represent in Sorensen’s Coefficient (CC)?
C = The no. of species the two communities have in common
S1 = The total no. of species found in community 1
S2 = The total no. of species found in community 2
Interpret the values for Sorensen’s Coefficient (CC)
Values will lie between 0 and 1
The closer the value is to 1 the more the two communities (S1 & S2) have in common.
Complete community overlap = 1
Complete community dissimilarity = 0
