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Species diversity overview and explained
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- 2. Species Diversity Species Diversity Measuring Diversity Measuring Diversity Scales Scales Richness Richness Diversity Diversity Eveness Eveness Patterns of Diversity Patterns of Diversity Latitudinal gradients Latitudinal gradients Elevational gradients Elevational gradients Precipitation gradients Precipitation gradients Peninsulas Peninsulas Aquatic environments Aquatic environments Processes Explaining Processes Explaining Diversity Gradients Diversity Gradients Historical Disturbance Historical Disturbance Hypothesis Hypothesis Equilibrium Theories Equilibrium Theories • Productivity Productivity • Climate stability Climate stability • Heterogeneity Heterogeneity • Biotic interaction Biotic interaction • Area/distance Area/distance Diversity in TRF Diversity in TRF • Equilibrium theory Equilibrium theory • Janzen’s hypothesis Janzen’s hypothesis • Non-Equilibrium theory Non-Equilibrium theory
- 3. Species Diversity: ANon-Concept? Species Diversity: A Non-Concept? What determines the number and kinds What determines the number and kinds of species that occur in a particular of species that occur in a particular place? place? Why do number and kinds of species Why do number and kinds of species vary from place to place? vary from place to place?
- 4. How many speciesare How many species are there? there?
- 5. How many speciesare How many species are there? there? Estimated No. of species in existence 8.7 million Only 1.2 million have been described
- 6. Scales of Diversity Scalesof Diversity Alpha Diversity Alpha Diversity w/in habitat w/in habitat Beta Diversity Beta Diversity b/w habitat b/w habitat Gamma Diversity Gamma Diversity Total diversity Total diversity
- 7. Species Species Forest habitat Foresthabitat Scrub Habitat Scrub Habitat Grassland habitat Grassland habitat A A x x B B x x C C x x D D x x E E x x F F x x x x G G x x x x H H x x x x I I x x x x J J x x x x K K x x L L x x x x M M x x N N x x Alpha Diversity Alpha Diversity Beta Diversity Beta Diversity Gamma Diversity Gamma Diversity
- 8. Species Species Forest habitat Foresthabitat scrub Habitat scrub Habitat Grassland habitat Grassland habitat A A x x B B x x C C x x D D x x E E x x F F x x x x G G x x x x H H x x x x I I x x x x J J x x x x K K x x L L x x x x M M x x N N x x Alpha Diversity Alpha Diversity 10 10 7 7 3 3 Beta Diversity Beta Diversity Gamma Diversity Gamma Diversity
- 9. Species Species Forest habitat Foresthabitat Scrub Habitat Scrub Habitat Grassland habitat Grassland habitat A A x x B B x x C C x x D D x x E E x x F F x x x x G G x x x x H H x x x x I I x x x x J J x x x x K K x x L L x x x x M M x x N N x x Alpha Diversity Alpha Diversity 10 10 7 7 3 3 Beta Diversity Beta Diversity (F vs. S) = 7 (F vs. S) = 7 Gamma Diversity Gamma Diversity
- 10. Species Species Forest habitat Foresthabitat Scrub Habitat Scrub Habitat Grassland habitat Grassland habitat A A x x B B x x C C x x D D x x E E x x F F x x x x G G x x x x H H x x x x I I x x x x J J x x x x K K x x L L x x x x M M x x N N x x Alpha Diversity Alpha Diversity 10 10 7 7 3 3 Beta Diversity Beta Diversity (F vs. S) = 7 (F vs. S) = 7 (S vs. G) = 8 (S vs. G) = 8 Gamma Diversity Gamma Diversity
- 11. Species Species Forest habitat Foresthabitat Scrub Habitat Scrub Habitat Grassland habitat Grassland habitat A A x x B B x x C C x x D D x x E E x x F F x x x x G G x x x x H H x x x x I I x x x x J J x x x x K K x x L L x x x x M M x x N N x x Alpha Diversity Alpha Diversity 10 10 7 7 3 3 Beta Diversity Beta Diversity (F vs. H) = 7 (F vs. H) = 7 (H vs. F) = 8 (H vs. F) = 8 (F vs. G) = 13 (F vs. G) = 13 Gamma Diversity Gamma Diversity
- 12. Species Species Forest habitat Foresthabitat Scrub Habitat Scrub Habitat Grassland habitat Grassland habitat A A x x B B x x C C x x D D x x E E x x F F x x x x G G x x x x H H x x x x I I x x x x J J x x x x K K x x L L x x x x M M x x N N x x Alpha Diversity Alpha Diversity 10 10 7 7 3 3 Beta Diversity Beta Diversity (W vs. H) = 7 (W vs. H) = 7 (H vs. F) = 8 (H vs. F) = 8 (F vs. W) = 13 (F vs. W) = 13 Gamma Diversity Gamma Diversity 14 14
- 13. Measuring Diversity Measuring Diversity Species Richness Species Richness Total number of species in an area Total number of species in an area can also be measured as biomass, basal area, % cover can also be measured as biomass, basal area, % cover Species Diversity Species Diversity Considers evenness and richness Considers evenness and richness Species Evenness Species Evenness Considers how abundance data are distributed among Considers how abundance data are distributed among the species the species A= 96 A= 96 F = 20 F = 20 B = 1 B = 1 G = 20 G = 20 C = 1 C = 1 H = 20 H = 20 D = 1 D = 1 I = 20 I = 20 E = 1 E = 1 J = 20 J = 20
- 14. Measuring Species Diversity MeasuringSpecies Diversity Species Richness Species Richness The number of species in a given area (N0) The number of species in a given area (N0) Sample Size Issue! Sample Size Issue! Margalef Index Menhinick Index Margalef Index Menhinick Index R1 = S-1/ln(n) R1 = S-1/ln(n) R2 = S/ n √ R2 = S/ n √ Where S = total number of species in area sampled Where S = total number of species in area sampled n = total number of individuals observed n = total number of individuals observed Interpretation: Interpretation: The higher the index the greater the richness The higher the index the greater the richness Example: S = 6 and n = 50 S = 6 and n = 20 R1 = 1.28 R1 = 1.66
- 15. Sampling area andspecies Sampling area and species richness richness Relationship b/w sampling area and bird species richness in North America)
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- 19. Measuring Species Diversity MeasuringSpecies Diversity Diversity Indices - Simpson’s Index Diversity Indices - Simpson’s Index = probability that 2 individuals selected = probability that 2 individuals selected at random will belong to the same species at random will belong to the same species = = i i(n (ni i(n (ni i-1))/N(N-1) -1))/N(N-1) Where: Where: n ni i= total number of individuals in each species = total number of individuals in each species N = Total number of individuals in all species N = Total number of individuals in all species Interpretation: Interpretation: If probability is high, the diversity of sample is low If probability is high, the diversity of sample is low
- 21. Measuring Species Diversity MeasuringSpecies Diversity Diversity Indices - Shannon’s Index Diversity Indices - Shannon’s Index H’ H’ H’= - H’= - i i ((n ((ni i/N) /N) ln (n ln (ni i/N)) /N)) Where: Where: n ni i= total number of individuals in each species = total number of individuals in each species N = Total number of individuals in all species N = Total number of individuals in all species Interpretation: Interpretation: 1.5 (low richness/eveness) to 3.5 (high richness 1.5 (low richness/eveness) to 3.5 (high richness and eveness) and eveness)
- 23. Hill’s Family ofDiversity Hill’s Family of Diversity Numbers Numbers Units are given in numbers of species Units are given in numbers of species NO = total number of species in the sample NO = total number of species in the sample N1 = the number of abundant species N1 = the number of abundant species N2 = the number of N2 = the number of very very abundant species abundant species N1 = e N1 = eH’ H’ (H’=Shannon’s index) (H’=Shannon’s index) the value of e 2.718 the value of e 2.718 N2 = 1/ N2 = 1/ ( ( =Simpson’s index) =Simpson’s index)
- 25. Measuring Species Diversity MeasuringSpecies Diversity Species Eveness Species Eveness How abundance data are distributed among species How abundance data are distributed among species A= 96 A= 96 F = 20 F = 20 B = 1 B = 1 G = 20 G = 20 C = 1 C = 1 H = 20 H = 20 D = 1 D = 1 I = 20 I = 20 E = 1 E = 1 J = 20 J = 20 E1 E1 Pielou’s J (1975) Pielou’s J (1975) In (N1)/ln (N0) In (N1)/ln (N0) Where: N1 = e Where: N1 = eH’ H’ N2 = 1/ N2 = 1/ E2 Sheldon (1969) E2 Sheldon (1969) N1/N0 N1/N0 E3 Heip (1974) E3 Heip (1974) N1-1/N0-1 N1-1/N0-1 E4 Hill (1973) E4 Hill (1973) N2/N1 N2/N1 E5 Modified Hill’s Ratio E5 Modified Hill’s Ratio N2-1/N1-1 N2-1/N1-1 Interpretation: Interpretation: 0 = less even, 1 = more even 0 = less even, 1 = more even
- 27. Desert Lizard Diversity DesertLizard Diversity Lizard Species Number of Individuals Cnemidophorus tesselatus 3 Cnemidophorus tigris 15 Crotophytus wislizenii 1 Holbrookia maculata 1 Phrynosoma cornutum 10 Scleoporus magister 2 TOTAL Individuals 32 Number of individuals for each of 6 species of lizards counted in a 1 hectare plot
- 28. Desert Lizard Diversity DesertLizard Diversity N2 = N1 = R2 = H’ = R1 = E5 = = NO = Eveness Diversity Richness
- 29. Desert Lizard Diversity DesertLizard Diversity N2 = 3 N1 = 4 R2 = 1.06 H’ = 1.33 R1 = 1.44 E5 = 0.80 = 0.31 NO = 6 Eveness Diversity Richness
- 30. Patterns of Diversity Patternsof Diversity Latitudinal Gradients Latitudinal Gradients Elevation Gradients Elevation Gradients Precipitation Gradients Precipitation Gradients Peninsulas Peninsulas Aquatic Environments Aquatic Environments
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- 38. Processes Explaining Diversity ProcessesExplaining Diversity Gradients Gradients • • Historical Disturbance Hypothesis Historical Disturbance Hypothesis - - landscape reflects historical events, not current landscape reflects historical events, not current environmental conditions (not in equilibrium) environmental conditions (not in equilibrium) Habitats catastrophically disturbed are “under saturated” in terms of Habitats catastrophically disturbed are “under saturated” in terms of species because there hasn’t been adequate time for adaptation and species because there hasn’t been adequate time for adaptation and speciation speciation Problems: evidence from tropics Problems: evidence from tropics
- 39. Extent of tropicsduring last glacial Extent of tropics during last glacial maximum maximum
- 40. Equilibrium Theories EquilibriumTheories Landscape is a reflection of current Landscape is a reflection of current environmental conditions (in equilibrium) environmental conditions (in equilibrium) • Productivity Productivity • Climate stability-Harsh habitat Climate stability-Harsh habitat • Habitat heterogeneity Habitat heterogeneity • Biotic interactions Biotic interactions • Large Area Large Area Processes Explaining Diversity Processes Explaining Diversity Gradients Gradients
- 41. Productivity Productivity What isthe link b/w productivity and What is the link b/w productivity and biodiversity? biodiversity? • Tropics 2200 g/m2/yr Tropics 2200 g/m2/yr • Temperate 1200 g/m2/yr Temperate 1200 g/m2/yr • Boreal 800 g/m2/yr Boreal 800 g/m2/yr Scale Scale • Estuaries, marshes are most productive Estuaries, marshes are most productive ecosystems on earth, with lowest diversity ecosystems on earth, with lowest diversity Processes Explaining Diversity Processes Explaining Diversity Gradients Gradients
- 42. Climate Stability(Harsh Habitat) Climate Stability (Harsh Habitat) Environments with low stability are harsher Environments with low stability are harsher and are less diverse and are less diverse Why? Why? Exceptions Exceptions • Areas with stable climate but low diversity Areas with stable climate but low diversity Processes Explaining Diversity Processes Explaining Diversity Gradients Gradients
- 43. Habitat Diversity(Heterogeneity) Habitat Diversity (Heterogeneity) What is the link? What is the link? Is it a direct relationship? Is it a direct relationship? Processes Explaining Diversity Processes Explaining Diversity Gradients Gradients
- 44. Biotic Interactions BioticInteractions Is speciation driven by competition in low Is speciation driven by competition in low lats and adaptation to physical stress in lats and adaptation to physical stress in high lats? high lats? • Exceptions: trees/plants Exceptions: trees/plants What about predation as a mechanism? What about predation as a mechanism? Circularity Circularity Processes Explaining Diversity Processes Explaining Diversity Gradients Gradients
- 45. Large LandArea Large Land Area Supports more individuals Supports more individuals Supports more species Supports more species Tropics? Boreal? Tropics? Boreal? Processes Explaining Diversity Processes Explaining Diversity Gradients Gradients
- 46. Diversity in TRFand Coral Reefs Diversity in TRF and Coral Reefs Equilibrium Viewpoint Equilibrium Viewpoint Stability is the major characteristic of a Stability is the major characteristic of a community. Following disturbance, it community. Following disturbance, it recovers and high diversity is maintained by a recovers and high diversity is maintained by a variety of mechanisms. Community reflects variety of mechanisms. Community reflects current conditions. current conditions. Non-Equilibrium Viewpoint Non-Equilibrium Viewpoint Communities rarely reach an equilibrium state Communities rarely reach an equilibrium state and high diversity results from changing and high diversity results from changing environmental conditions. environmental conditions.
- 47. Diversity in TRF Diversityin TRF • • Janzen’s Hypothesis (1970): Biotic interactions Janzen’s Hypothesis (1970): Biotic interactions - host-specific herbivores - host-specific herbivores - seed predation - seed predation - canopy foliovores - canopy foliovores • • Hubbell’s research (1979, 1980) to support Janzen Hubbell’s research (1979, 1980) to support Janzen • • Non-equilbrium explanation (Connell 1978) Non-equilbrium explanation (Connell 1978) - coral reefs - coral reefs
- 50. The Non-Equilibrium Hypothesis TheNon-Equilibrium Hypothesis (Connell 1978) (Connell 1978) Intermediate Disturbance Hypothesis Intermediate Disturbance Hypothesis
- 52. The Non-Equilibrium Hypothesis TheNon-Equilibrium Hypothesis (Connell 1978) (Connell 1978) Connell’s Conclusions Connell’s Conclusions TRF and Coral Reefs demonstrate Non- TRF and Coral Reefs demonstrate Non- Equilibrium Hypothesis Equilibrium Hypothesis Equilibrium and Non-Equilibrium are not Equilibrium and Non-Equilibrium are not mutually exclusive mutually exclusive Role of human disturbances Role of human disturbances
- 53. More Intermediate Disturbance MoreIntermediate Disturbance Hypothesis (Denslow 1980) Hypothesis (Denslow 1980) Intermediate levels of disturbance vary by Intermediate levels of disturbance vary by ecosystem ecosystem Ecosyste m Historic Rate of Disturbance (years) Prairie 2 Chaparral 30 Pine 50 Oak-HW 50-100 Spruce-Fir 1000
Editor's Notes
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