1. Species diversity
Species diversity: variation in types of organisms present in a community
Components of species diversity
species richness: number of species present
heterogeneity or equitability of species: how equally distributed in the community are the abundances of individual species

2. Measurement of species diversity
Species diversity indices: Table 5B.1, p. 178
Species richness
number of species in the community
simplest estimate
count only resident species, not accidentals
gives all species same “importance”, regardless of number of individuals present

3. Measurement of species diversity
Heterogeneity of species in the community
attempt to overcome problem of considering common and rare species as having same “importance” in the community
uses relative abundance

4. Measurement of species diversity
Heterogeneity of species in the community
e.g., two communities with two species and the same total number of individuals could be comprised of two extremes:
Community 1 Community 2
Species A
Species B
heterogeneity increases in a community when there are more species and when the species are equally abundant (heterogeneous)

5. Measurement of species diversity
Shannon-Wiener function
measurement of species diversity using
species richness (number of species)
relative abundance (heterogeneity)
H’ = - (pi)[ln(pi)]
where H’ = Shannon-wiener index of species diversity
s = number of species in the community
pi = proportion of total abundance represented by the ith species

6. Measurement of species diversity
BIOL 4233 and BIOL Experiment 2
Measurement of species diversity
Shannon-Weiner species diversity calculations for the two 2-species communities:
Community 1
Community 2 N pi
ln(pi)
pi[ln(pi)]
Species A 99
0.99
-0.010 50
0.50
-0.693
-0.347
Species B 1
0.01
-4.605
-0.046
Total
100
-0.056
-0.694 H’
0.056
0.694

7. Measurement of species diversity
Shannon-Wiener index
values range from near zero to ???
higher index values indicate higher species diversity
index has no units, has value only when comparing communities
increasing the number of species (s) increases H’
increasing the equitability (heterogeneity) of the species in the community increases H’

8. Measurement of species diversity
Evenness
measurement of equitability among species in the community
E = H’ / Hmax
where E = Pielou’s index of evenness
H’ = calculated Shannon-wiener index
Hmax = ln(s) = species diversity under maximum equitability conditions
s = number of species in the community

9. Measurement of species diversity
Evenness
values range from 0 to 1
for the two 2-species communities example:
Community Community 2 s H’
Hmax E

10. Measurement of species diversity
Simpson’s index
measurement of dominance and diversity
uses number of species and relative abundance of species
if two individuals are sampled at random within a community, the probability that the two will belong to the same species is
I = ni (ni-1) / N (N-1)
where ni = number of individuals of the ith species N = total number of individuals

11. Measurement of species diversity
Simpson’s index
the quantity I is a measure of dominance or the concentration of N individuals among s species
Ds = 1 - I
Ds = 1 – [ni (ni-1) / N (N-1)]
where Ds = Simpson’s dominance index
ni = number of individuals of the ith species N = total number of individuals

12. Measurement of community similarity
Jaccard’s coefficient of community similarity
CCJ = c / (s1 + s2 + sn – c)
CCJ = c / S
where CCJ = Jaccard’s coefficient of community
s1 = number of species in community 1
s2 = number of species in community 2
sn = number of species in communities n
c = number of species common in all communities
S = total number of species found in all communities

13. Experiment 2 Comparative species diversity
small nekton community associated with salt marshes in the Galveston Bay system
objectives
compare species diversity and species composition at one site (Hance Bayou) between two collection times: October 2010 and September 1999
Shannon Weiner diversity
Pielou evenness,
Jaccard’s coefficient of similarity
Simpson’s dominance
compare fish size (age class) among the three sites
compare differences in biotic indices among sites to differences in physical and chemical environment

14. Experiment 2 Comparative species diversity variables water quality
salinity
temperature pH
total dissolved solids (TDS)
physical environment
wind direction and speed
tide level
structures
biological environment

15. You are here!

16. I-45 3
Virginia Point 2
Hance Bayou 1
Christmas Bay

17. Comparative Species DiversityN
BIOL 4233 and 5533
Field Trip for Expt 2
Comparative Species Diversity
Date: Monday, 10/04/10
Meet at 8:00 am sharp at the Bright Light bait store just west of the San Luis Pass bridge
Site 3: Virginia Point
I-45
To Houston
Map is not
to scale!
West Galveston Bay
Galveston
Sportsman's Rd.
Site 2: Hance Bayou
61st St.
Bright Light
Bait Store
8-mile
Rd.
Stewart
Rd.
Seawall
Blvd.
Site 1: Christmas Bay
FM3005
Flashing light
Gulf of Mexico
San Luis Pass bridge
$2 toll each way