What are the causes and consequences of variation in diversity?

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 do diversity and stability covary in lake zooplankton assemblages? • How is diversity related to environmental variability? • Does regional diversity stabilize ecosystems? • Patrick Thompson’s M.Sc. thesis

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. A simple modelShurin 2007 Oikos • Species blink in and out • Diversity affects invasion and extinction • invasion resistance • facilitation • Environmental variation affects invasion and extinction • storage effects, variability enhances coexistence • stochastic extinction, variability prevents coexistence

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

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

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

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

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

16. 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

17. 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?

18. How to measure environmental variability Clearwater Lake, Ontario date

19. The data set

20. 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

21. 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

22. 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 1,042 years 5,932 monthly samples

23. 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 = residual or unpredictable component

24. 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 = residual or unpredictable component Standard Deviation measures variance on each time scale }

25. The interannual component

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

27. deviation from the mean

28. Conductivity has high interannual variation

29. Total nitrogen has low seasonal variation

30. Temperature has high seasonal variation

31. Low and high variability lakes- pH

32. Low and high variability lakes- pH

33. Low and high variability lakes- temperature

34. Low and high variability lakes- temperature

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

36. Zooplankton species richness and mean environmental conditions

37. Zooplankton species richness and interannual variability

38. Zooplankton species richness and seasonal variability

39. 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

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

41. 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

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

43. How does diversity affect ecosystem resilience?

44. How does diversity affect ecosystem resilience? • Local diversity affects stability, but who cares? • Regional diversity may matter in a changing environment • Pool of diverse traits for any occasion

45. Experimental design • 2 x 2 x 2 factorial • warming (2.5 ºC) • salinity (3 ppt) • dispersal of regional zooplankton species

47. Interactive effects of warming and dispersal on zooplankton composition

48. Interactive effects of warming and dispersal on ecosystem processes

49. No interactive effects of salinity and dispersal on ecosystem processes

50. Why regional diversity was more important in the warming treatment