Biodiversity indices and IBI

2. Biodiversity indices
 A diversity index is a mathematical measure of species
diversity in a given community.
 Based on the species richness (the number of species present)
and species abundance (the number of individuals per species).
 These indices are statistical representations of biodiversity in
different aspects (richness, evenness, and dominance).

3. What is biodiversity?
In simplest form, biodiversity is the variety of different types of
organisms present and interacting in an ecosystem.

4.  Diversity usually implies a measure of both species number
and ‘equitability’ (or ‘evenness’).
1. Species richness indices
 Species richness is a measure for the total number of the
species in a community.

5. 2. Evenness indices:
 Evenness expresses how evenly the individuals in a
community are distributed among the different species.

6. Why is biodiversity measured?
 It is a measure that combines richness and evenness across
species.
 High diversity is synonymous with ecosystem health.
 Diverse communities have increased stability, increased
productivity, and resistance to invasion and other disturbances.

7. These three types of indices can be used on different spatial scales
1. Alpha diversity
 Alpha diversity refers to diversity within a particular area,
community or ecosystem, and is usually measured by counting
the number of taxa within the ecosystem (usually species
level).
2. Beta diversity
 Beta diversity is species diversity between ecosystems; this
involves comparing the number of taxa that are unique to each
of the ecosystems.

8. 3. Gamma diversity
 Gamma diversity is a measure of the overall diversity for
different ecosystems within a region.

9. Many different indices of diversity are used
Simpson’s Index
 Simpson (1949) developed an index of diversity which is a
measure of probability the less diversity, the greater the
probability that two randomly selected individuals will be the
same species.
 In the absence of diversity (1 species), the probability that two
individuals randomly selected will be the same is 1.

10. Index is calculated as follows:
 n = the total number of organisms of a particular species
 N = the total number of organisms of all species .
 The value of D ranges between 0 and 1.
 With this index, 1 represents infinite diversity and 0, no
diversity, so the larger the value of D, the lower the diversity.

11. Shannon-Weiner Index
 Another widely used index of diversity that also considers
both species richness and evenness is the Shannon-Weiner
Diversity Index.
 Originally proposed by Claude Shannon in 1948. It is also
known as Shannon's diversity index.
 The index is related to the concept of uncertainty.

12. Index is calculated as follows:
 where pi = proportion of individuals of species i , and ln is the
natural logarithm, and S = species richness.
 The value of H ranges from 0 to Hmax . Hmax is different for
each community and depends on species richness.

13. Evenness Index
 Species evenness refers to how close in numbers each species
in an environment is. So if there are 40 foxes and 1000 dogs,
the community is not very even.
 But if there are 40 foxes and 42 dogs, the community is quite
even. The evenness of a community can be represented by
Pielou's evenness index (Pielou 1966).

14. Index is calculated as follows:
J= H/Hmax
 The value of J ranges from 0 to 1. Higher values indicate
higher levels of evenness. At maximum evenness, J = 1.
 J and D can be used as measures of species dominance in a
community. Low J indicates that 1 or few species dominate the
community.

15. Index of biotic integrity
• An Index of Biological Integrity (IBI) is a synthesis of diverse
biological information which numerically depicts associations
between human influence and biological attributes.
• A scientific tool used to identify and classify water pollution
problems.
• The IBI concept was formulated by Dr. James Karr in 1981.

16. History
 Water quality act (1972) stimulated many efforts to monitor
the quality of water resource systems.
 It resulted in development of thresholds and criteria levels foe
specific contaminants, often based on acute toxicity tests.

17.  “Biotic integrity” is based on the premise that the status of
living organisms provides the most direct and effective
measure of the integrity of water.
 The Index of Biotic Integrity (IBI) provides managers with a
technique for evaluating the biological condition of the water
resource.
 As the IBI became widely used, different versions were
developed for different regions and ecosystems.

18. Living systems, such as fish used in the IBI, are useful in
measuring degradation for many reasons:
 Fish are sensitive to a wide array of stresses.
 Fish integrate adverse effects of activities in the watershed.
 Fish are long-lived; their populations show effects of
reproductive failure and mortality in many age groups and
therefore provide a long-term record of environmental
stressors.

19. IBI system
• The original version had 12 metrics that reflected fish species
richness 2 and composition, number and abundance of species,
trophic organization and function, reproductive behavior, fish
abundance, and condition of individual fish.
• The metrics were scored and summed to arrive at an index
ranging from 60 (best) to 12 (worst).

20. Example of metrics used to construct an Index of
Biotic Integrity (IBI)
Metric Description
Number of fish species
and individuals
The total number of species and
individuals supported by the
stream will decrease with
environmental degradation
Number of darters Darters are sensitive to
environmental degradation.
Darter habitats may be degraded
as the result of siltation,
channelization, etc.

21. Number of species of sunfish These species are particularly sensitive to
silting in of pools and loss of in-stream cover.
Number of species of suckers Suckers are intolerant of chemical and habitat
degradation and because they are long lived
provide a multiyear perspective
Number of intolerant species Intolerant species are most affected by stream
degradation and therefore would disappear by
the time a stream is rated as ‘fair’.
Percentage of tolerant species Tolerant species are present in moderate
number but become dominant as stream
degrades.
Percentage of diseased fish Skeletal anomalies, fin damage, disease, and
tumors increase with stream degradation.

22. Biotic integrity classes
Class Attributes
Excellent Comparable to the best situations without
influences of man, with most intolerant
forms, full array of age and sex classes,
balanced trophic structure
Good Species richness somewhat below
expectation, loss of most intolerant forms,
trophic structure shows some sign of stress
Fair Sign of additional deterioration include
fewer intolerant forms, more skewed trophic
structure

23. Poor Dominated by omnivores, pollution tolerant
forms and habitat generalists, growth rate
and condition factors commonly depressed,
hybrid and diseased fish often present
Very poor Few fish present, mostly introduced or very
tolerant forms, hybrids common, disease, fin
damage, other anomalies regular
No fish Repetitive sampling fails to turn up any fish

24. Parameters used in assessment of fish communities
Species composition and
richness
• Number of species
• Presence of intolerant
species
• Species richness and
composition of Darters,
Sucker, Sunfish
• Proportion of hybrid
individuals
Ecological factor
• No. of individuals in sample
• Proportion of omnivores
• Proportion of insectivores
• Proportion of top carnivores
• Proportion with disease,
tumor, fin damage other
anomalies

25. References
 Biodiversity Indexes: Value and Evaluation Purposes, Jatna
Supriatna, Institute for Sustainable Earth and Resources (I-SER)
and Dept of Biology, Faculty of Math and Sciences, Universitas
Indonesia.
Application of the Index of Biotic Integrity to Evaluate Water
Resource Integrity in Freshwater Ecosystems, Thomas P. Simon
and John Lyons.
Biodiversity indices, Jitendra Kumar, Neeraj Pathak, Ramesh
Kumar Tripathi, Archit Shukla, Saurabh Dubey, College of
Fisheries, Mangalore, College of Fisheries, Veraval, Central
Institute of Fisheries Education, Mumbai, College of
Fisheries, Ludhiana, Punjab.

26. THANKYOU