1. Communities: Quantifying community structure. Mary E. Allen Hartwick College

2. Communities assemblage of organisms living together in the same geographic location Interactions: competition, predation, parasitism, etc. Diversity: number of different types; relative abundances

3. Acquiring a Good Measure of Species Diversity Requires habitat is sampled often enough that all of the species are detected, including those that are rare So how many samples are enough? Depends upon: –how many species are present in a community –in what numbers species are present

4. How do we know we have adequately sampled species richness? How many samples were necessary?

5. Species Sample Curves for 3 Different Communities Was the number of necessary samples the same for all 3 communities?

6. Quantifying Diversity of a Community Species Richness: number of species present in the community More species = higher species diversity

7. Species Richness

8. Quantifying Diversity of a Community Species Evenness: relative abundances of species in a community Greater evenness = higher diversity

9. Species Evenness

10. Quantifying Diversity Simpson’s Index D = Σ (n i /N) n i = number of individuals of species i N = total number of individuals of all species Simpson’s index of diversity = 1 – D - value increases with diversity