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Species abundance and diversity (Ch. 16)

Species abundance and diversity (Ch. 16). New Unit: Communities/Ecosystems. Community : Interacting species in defined area. Functional groups: subdivide organisms based on life history Guild : Organisms living in same fashion Animal Ex.: granivore guild. Harvester ants. K-rat.

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Species abundance and diversity (Ch. 16)

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  1. Species abundance and diversity (Ch. 16)

  2. New Unit: Communities/Ecosystems • Community: Interacting species in defined area. • Functional groups: subdivide organisms based on life history • Guild: Organisms living in same fashion • Animal Ex.: granivore guild Harvester ants K-rat

  3. New Unit: Communities/Ecosystems • Growth form: Combination structure + growth pattern. • Ex.: tree, shrub, graminoid, forb, climber

  4. Species Abundance • How express? • Log abundance (x-axis), number species in abundance category (y-axis) • Ex, plant species (% cover measures abundance) • Ex, bird species (counts measure abundance) Curve?

  5. Species Abundance • Normal (bell-shaped) curve • x-axis log scale: lognormal distributions

  6. Species Abundance • Often only part curve seen. • Why? Sample size. • Ex, moth community & sample size Tiger moth (Arctiidae) Sphingid moth (Sphingidae)

  7. Species Diversity • Two factors: • 1) Species Richness • Number species

  8. Species Diversity • Two factors: • 2) Species Evenness • Relative abundance of species

  9. Species Diversity • How integrate? • Diversity Index. Gives single number

  10. Species Diversity • Common: Shannon Wiener Index • Fish diversity lab! Ecology SU 2005

  11. Species Diversity • Shannon Wiener Index: s H´ = - pi logepi i=l • H´ = Value of index • pi = Proportion individuals of ith species • loge = Natural log • S = Number species in community

  12. Species Diversity • Ex: b greater diversity (same richness)

  13. Rank Abundance Curves • Rank abundance curves: • Relative abundance (proportional abundance: y-axis, log scale) vs. abundance rank (x-axis) • a vs. b

  14. Rank Abundance Curves • Ex: reef fish communities (Gulf of California)

  15. Rank Abundance Curves • Which more diverse? (Richness, evenness)

  16. Environmental Complexity • In general: diversity increases with environmental complexity (heterogeneity) • Ex, warblers (eat insects on trees) • Environmental complexity • = foliage volume

  17. Environmental Complexity • Foliage height diversity correlates positively bird species diversity

  18. Environmental Complexity • Hutchinson (1961): • Phytoplankton: simple environments, compete same nutrients • But many species coexist

  19. Environmental Complexity • Algal niches. • Ex, Diatoms (Protists, Phylum Bacillariophyta) • Photosynthetic • Cell walls: silicate

  20. Environmental Complexity • Coexistence depends on ratio silicate:phosphate • Different niches: different diatoms dominate

  21. Environmental Complexity • Do nutrients vary in “real world?” • Ex, Pyramid Lake, Nevada

  22. Environmental Complexity • Ex, Pyramid Lake, Nevada

  23. Environmental Complexity • Tropical rain forest diversity? • Amazon: 1 hectare (2.47 acres) up to 750 tree species USA has 850 native tree species!

  24. Environmental Complexity • Diversity due to: • 1) many species per community • 2) many communities per unit area • Complexity helps explain diversity

  25. Environmental Complexity • Relationship nutrients and rainforest richness? • Negative! • Competitive exclusion by best competitors

  26. Environmental Complexity • Reducing environmental complexity • When humans add nutrients (intentionally or not!) • Reduces diversity • Reduces limiting nutrients

  27. Environmental Complexity • Ex, English grassland fertilized since 1856!

  28. Environmental Complexity • Ex, N fertilization & ectomycorrhizal fungi diversity • N aerial pollutant (Alaska factory)

  29. Environmental Complexity • Contributes to diversity • But so does…disturbance • Define??

  30. Disturbance and Diversity • Disturbance: departure from “average?” • Sousa: • Discrete, punctuated, killing, displacement, or damaging of individuals that directly or indirectly creates an opportunity for new individuals to establish. • White and Pickett: • Relatively discrete event that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or physical environment.

  31. Disturbance and Diversity • Two major characteristics: • Frequency (how often) • Intensity (how severe) • Abiotic: fire, hurricanes, ice storms, flash floods • Biotic: disease, predation, humans

  32. Intermediate Disturbance Hypothesis

  33. Intermediate Disturbance • Ex: intertidal zone • Disturbance depends on boulder size.

  34. Intermediate Disturbance • Richness greater medium boulders

  35. Temperate Grasslands • American prairie dog disturbance….

  36. Disturbance

  37. Disturbance • Prairie dog control: reduced populations 98%

  38. Humans as disturbance • Human disturbance & diversity • Ex, chalk grasslands (Europe) • Graze livestock, cut hay • What happened when “protected”?

  39. Humans as a disturbance • Diversity dropped (Brachypodium dominated)

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