1. Biogeography November 7-14, 2007
Species Diversity
Biogeography
November 7-14, 2007

2. Geographical Ecology Ecological Patterns Ecological Processes
Species diversity
Species distributions
Island patterns
Community distributions
Ecological Processes
Competition
Coexistence
Succession
disturbance

3. Species Diversity Measuring Diversity
Scales
Richness
Diversity
Eveness
Patterns of Diversity
Latitudinal gradients
Elevational gradients
Precipitation gradients
Peninsulas
Aquatic environments
Processes Explaining Diversity Gradients
Historical Disturbance Hypothesis
Equilibrium Theories
Productivity
Climate stability
Heterogeneity
Biotic interaction
Area/distance
Diversity in TRF
Equilibrium theory
Janzen’s hypothesis
Non-Equilibrium theory

4. Species Diversity: A Non-Concept?
What determines the number and kinds of species that occur in a particular place?
Why do number and kinds of species vary from place to place?

5. How many species are there?

6. How many species are there?

7. Scales of Diversity Alpha Diversity Beta Diversity Gamma Diversity
w/in habitat
Beta Diversity
b/w habitat
Gamma Diversity
Total diversity

8. Species Woodland habitat Hedgerow Habitat Open field habitat A B C D Ex B C D E F G H I J K L M N
Alpha Diversity
Beta Diversity
Gamma Diversity

9. 10 7 3 Species Woodland habitat Hedgerow Habitat Open field habitat Ax B C D E F G H I J K L M N
Alpha Diversity 10 7 3
Beta Diversity
Gamma Diversity

10. 10 7 3 (W vs. H) = 7 Species Woodland habitat Hedgerow Habitat
Open field habitat A x B C D E F G H I J K L M N
Alpha Diversity 10 7 3
Beta Diversity
(W vs. H) = 7
Gamma Diversity

11. 10 7 3 (W vs. H) = 7 (H vs. F) = 8 Species Woodland habitat
Hedgerow Habitat
Open field habitat A x B C D E F G H I J K L M N
Alpha Diversity 10 7 3
Beta Diversity
(W vs. H) = 7
(H vs. F) = 8
Gamma Diversity

12. 10 7 3 (W vs. H) = 7 (H vs. F) = 8 (F vs. W) = 13
Species
Woodland habitat
Hedgerow Habitat
Open field habitat A x B C D E F G H I J K L M N
Alpha Diversity 10 7 3
Beta Diversity
(W vs. H) = 7
(H vs. F) = 8
(F vs. W) = 13
Gamma Diversity

13. 10 7 3 (W vs. H) = 7 (H vs. F) = 8 (F vs. W) = 13 14
Species
Woodland habitat
Hedgerow Habitat
Open field habitat A x B C D E F G H I J K L M N
Alpha Diversity 10 7 3
Beta Diversity
(W vs. H) = 7
(H vs. F) = 8
(F vs. W) = 13
Gamma Diversity 14

14. Sampling area and species richness
Relationship b/w sampling area and bird species richness in North America (Fig MacDonald)

15. Measuring Diversity Species Richness Species Diversity Species Eveness
Total number of species in an area
can also be measured as biomass, basal area, % cover
Species Diversity
Considers eveness and richness
Species Eveness
Considers how abundance data are distributed among the species
96 humans, 1 dodo, 1 thylacine, 1 honeycreeper, 1 chuckwalla
20 peccaries, 20 monkeys, 20 leafcutter ants, 20 wasps, 20 lizards

16. Measuring Species Diversity
Species Richness
The number of species in a given area (N0)
Sample Size Issue!
Margalef Index Mehinick Index
R1 = S-1/ln(n) R2 = S/√n
Where S = total number of species in area sampled
n = total number of individuals observed
Interpretation:
The higher the index the greater the richness
R1 = 1.28
R1 = 1.66
Example: S = 6 and n = 50
S = 6 and n = 20

19. Measuring Species Diversity
Diversity Indices - Simpson’s Index 
 = probability that 2 individuals selected
at random will belong to the same species
= i(ni(ni-1))/N(N-1)
Where:
ni= total number of individuals in each species
N = Total number of individuals in all species
Interpretation:
If probability is high, the diversity of sample is low

20. Measuring Species Diversity
Diversity Indices - Shannon’s Index H’
H’= -i ((ni/N) ln (ni/N))
Where:
ni= total number of individuals in each species
N = Total number of individuals in all species
Interpretation:
1.5 (low richness/eveness) to 3.5 (high richness and eveness)

21. Hill’s Family of Diversity Numbers
Units are given in numbers of species
NO = total number of species in the sample
N1 = the number of abundant species
N2 = the number of very abundant species
N1 = eH’ (H’=Shannon’s index)
N2 = 1/ (=Simpson’s index)

23. Measuring Species Diversity
Species Eveness
How abundance data are distributed among species
96 humans, 1 dodo, 1 thylacine, 1 honeycreeper, 1 chuckwalla
20 peccaries, 20 monkeys, 20 leafcutter ants, 20 wasps, 20 lizards
Modified Hill’s Ratio E5 = N2-1/N1-1
Where: N1 = eH’ N2 = 1/
Interpretation:
0 = less even, 1 = more even

25. Desert Lizard Diversity
Number of individuals for each of 6 species
of lizards counted in a 1 hectare plot
Lizard Species
Number of Individuals
Cnemidophorus tesselatus 3
Cnemidophorus tigris 15
Crotophytus wislizenii 1
Holbrookia maculata
Phrynosoma cornutum 10
Scleoporus magister 2
TOTAL Individuals 32

26. Desert Lizard Diversity
Richness
Diversity
Eveness
NO =
 =
E5 =
R1 =
H’ =
R2 =
N1 =
N2 =

27. Desert Lizard Diversity
Richness
Diversity
Eveness
NO = 6
 = 0.31
E5 = 0.80
R1 = 1.44
H’ = 1.33
R2 = 1.06
N1 = 4
N2 = 3

28. Patterns of Diversity Latitudinal Gradients Elevation Gradients
Precipitation Gradients
Peninsulas
Aquatic Environments

29. Mammals
Birds

37. Processes Explaining Diversity Gradients
• Historical Disturbance Hypothesis
- landscape reflects historical events, not current
environmental conditions (not in equilibrium)
Habitats catastrophically disturbed are “undersaturated” in terms of species because there hasn’t been adequate time for adaptation and speciation
Problems: evidence from tropics

38. Extent of tropics during last glacial maximum

39. Processes Explaining Diversity Gradients
Equilibrium Theories
Landscape is a reflection of current environmental conditions (in equilibrium)
Productivity
Climate stability-Harsh habitat
Habitat heterogeneity
Biotic interactions
Large Area

40. Processes Explaining Diversity Gradients
Productivity
What is the link b/w productivity and biodiversity?
Tropics 2200 g/m2/yr
Temperate 1200 g/m2/yr
Boreal 800 g/m2/yr
Scale
Estuaries, marshes are most productive ecosystems on earth, with lowest diversity

41. Processes Explaining Diversity Gradients
Climate Stability (Harsh Habitat)
Environments with low stability are harsher and are less diverse
Why?
Exceptions
Areas with stable climate but low diversity

42. Processes Explaining Diversity Gradients
Habitat Diversity (Heterogeneity)
What is the link?
Is it a direct relationship?

43. Processes Explaining Diversity Gradients
Biotic Interactions
Is speciation driven by competition in low lats and adaptation to physical stress in high lats?
Exceptions: trees/plants
What about predation as a mechanism?
Circularity

44. Processes Explaining Diversity Gradients
Large Land Area
Supports more individs
Supports more species
Tropics? Boreal? .

45. Diversity in TRF and Coral Reefs
Equilibrium Viewpoint
Stability is the major characteristic of a community. Following disturbance, it recovers and high diversity is maintained by a variety of mechanisms. Community reflects current conditions.
Non-Equilibrium Viewpoint
Communities rarely reach an equilibrium state and high diversity results from changing environmental conditions.

46. Diversity in TRF • Janzen’s Hypothesis (1970): Biotic interactions
- host-specific herbivores
- seed predation
- canopy foliovores
• Hubbell’s research (1979, 1980) to support Janzen
• Non-equilbrium explanation (Connell 1978)
- coral reefs

49. The Non-Equilibrium Hypothesis (Connell 1978)
Intermediate Disturbance Hypothesis

51. The Non-Equilibrium Hypothesis (Connell 1978)
Connell’s Conclusions
TRF and Coral Reefs demonstrate Non-Equilibrium Hypothesis
Equilibrium and Non-Equilibrium are not mutually exclusive
Bottom line is:
Role of human disturbances

52. More Intermediate Disturbance Hypothesis (Denslow 1980)
Intermediate levels of disturbance vary by ecosystem
Ecosystem
Historic Rate of
Disturbance (years)
Prairie 2
Chaparral 30
Pine 50
Oak-HW
50-100
Spruce-Fir
1000