What are the causes and consequences of variation in diversity? - PowerPoint PPT Presentation

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What are the causes and consequences of variation in diversity?

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  1. What are the causes and consequences of variation in diversity?

  2. What are the causes and consequences of variation in diversity? How is diversity related to temporal variability?

  3. stability diversity History of ideas on diversity and stability • Wild speculation- • Elton 1958 • MacArthur 1955 “Stability increases as the number of links increases. If the number of prey species for each species remains constant, an increase in the number of species in the community will increase the stability.” -MacArthur 1955

  4. stability diversity History of ideas • Math defies intuition- • May 1973 • Gardner and Ashby 1970 More species = greater chance of including unstable combinations of strong interactions -> extinctions and fluctuations if interaction strength is uniformly distributed

  5. stability diversity History of ideas • The role of interaction strength • Yodzis 1981 • McCann et al. 1998 • Berlow 1999 “Early data unequivocally indicate that distributions of interaction strength are strongly skewed toward weak interactions. It seems, then, that weak interactions may be the glue that binds natural communities together” -McCann et al. 1998Nature

  6. stability stability stability diversity diversity diversity History of ideas • Wild speculation- • Math defies intuition- • The role of interaction strength-

  7. How are diversity and stability related in nature? What can species-time relations tell us about diversity and stability?

  8. Questions? • How is diversity related to community temporal stability? • Model • How do diversity and stability covary in lake zooplankton assemblages? • Data • How is diversity related to environmental variability? • Data

  9. 35 30 Daily richness 25 20 10 20 30 40 50 60 70 80 90 100 50 45 Cumulative richness 40 10 20 30 40 50 60 70 80 90 100 Time How do we measure stability?Species turnover a = daily richness z = turnover ST= long-term richness ST = aTz

  10. How do species partition time…if diversity is driven by history ? Shurin 2007 Oikos 116: 957

  11. How do species partition time…if diversity is driven by history ? total richness time time time Shurin 2007 Oikos 116: 957

  12. How do species partition time…if diversity is driven by history ? total richness time time time turnover daily richness total richness total richness Shurin 2007 Oikos 116: 957

  13. How do species partition time…if diversity prevents colonization ? total richness time time time turnover daily richness total richness total richness Shurin 2007 Oikos 116: 957

  14. How do species partition time…if diversity facilitates colonization ? total richness time time time turnover daily richness total richness total richness Shurin 2007 Oikos 116: 957

  15. How do species partition time…if environmental variability increases diversity? total richness time time time turnover daily richness total richness total richness Shurin 2007 Oikos 116: 957

  16. Model predictions: Correlation with long-term richness Shurin 2007 Oikos 116: 957

  17. And the data say… Toolik SE AK ELA Quebec Kodiak Dorsett Lake Geneva Washington Wisconsin 36 lakes 483 lake-years 5,364 samples

  18. Daily, annual and inter-annual richness Shurin et al. 2007 Ecology Letters 10: 127

  19. Richness and turnover Shurin et al. 2007 Ecology Letters 10: 127

  20. Richness and turnover Shurin et al. 2007 Ecology Letters 10: 127

  21. Richness and turnover Shurin et al. 2007 Ecology Letters 10: 127

  22. Conclusions • Feedbacks among diversity, invasion, extinction and the environment influence different aspects of species-time • Zooplankton show scale-dependent patterns • positive correlations within the temperate zone • negative correlations across latitudes

  23. Environmental stability and diversity-a double edged sword • Abiotic variability can either increase or decrease coexistence • Storage effects vs. geometric mean fitness What is the net effect of environmental variation on diversity?

  24. How to measure environmental variability Clearwater Lake, Ontario

  25. The data set

  26. The data set surface temperature bottom temperature chlorophyll a total nitrogen total phosphorus maximum O2 minimum O2 conductivity pH DOC + zooplankton species X 10 variables

  27. surface temperature bottom temperature chlorophyll a total nitrogen total phosphorus maximum O2 minimum O2 conductivity pH DOC + zooplankton species X 10 variables The data set X 53 lakes

  28. surface temperature bottom temperature chlorophyll a total nitrogen total phosphorus maximum O2 minimum O2 conductivity pH DOC + zooplankton species X 10 variables The data set X 53 lakes X 1,042 years 5,932 monthly samples

  29. How do we partition environmental variability among time scales? • Multiplicative model of variance decomposition: • Xt = XltAtStEt • Xlt = long-term mean • At = inter-annual component (XA/Xlt) • St = seasonal component (XM/XA) • Et = event or unpredictable component

  30. How do we partition environmental variability among time scales? • Multiplicative model of variance decomposition: • Xt = XltAtStEt • Xlt = long-term mean • At = inter-annual component (XA/Xlt) • St = seasonal component (XM/XA) • Et = event or unpredictable component } Standard Deviation measures variance on each time scale

  31. The interannual component

  32. The interannual component as deviation from the long-term mean

  33. Interannual = 0.14 Seasonal = 0.008 Residual = 0.02

  34. Conductivity has high interannual variation

  35. Total nitrogen has low seasonal variation

  36. Temperature has high seasonal variation

  37. Low and high variability lakes- pH

  38. Low and high variability lakes- pH

  39. Low and high variability lakes- temperature

  40. Low and high variability lakes- temperature

  41. How does variability relate to zooplankton diversity? • Long-term mean • Interannual variability • Seasonal variability • Residual (unpredictable) variability

  42. Zooplankton species richness and mean environmental conditions

  43. Zooplankton species richness and interannual variability

  44. Zooplankton species richness and seasonal variability

  45. Residual variability 16 16 14 14 12 12 zooplankton richness 10 10 8 8 6 6 4 4 0.0 0.1 0.2 0.3 0.4 0.5 -2.0 -1.5 -1.0 bottom temperature ln(TP) Zooplankton species richness and residual variability

  46. Interannual and residual variation are better predictors of diversityaverage conditions and seasonality- not so much

  47. Conclusions • Diversity mostly increases with greater thermal variability but declines with chemical instability • Environmental variability (especially interannual and unpredictable) are more important for diversity than average conditions

  48. Increasing frequency of extreme variationEasterling et al. 2000 Science birth of Jon

  49. Thanks • Helmut Hillebrand • Monika Winder • Rita Adrian • Bill Keller • Blake Matthews • Andrew Paterson • Michael Paterson • Bernadette Pinel-Alloul • Jim Rusak • Shelley Arnott • Allyson Longmuir • Norm Yan