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

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

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

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 99 50 Species B 1 50 heterogeneity increases in a community when there are more species and when the species are equally abundant (heterogeneous)

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

Measurement of species diversity BIOL 4233 and BIOL 5533 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

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’

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

Measurement of species diversity Evenness values range from 0 to 1 for the two 2-species communities example: Community 1 Community 2 s 2 2 H’ 0.056 0.694 Hmax 0.693 0.693 E 0.081 1.000

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

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

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

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

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

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

Comparative Species Diversity N 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