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What are the causes and consequences of variation in diversity? What are the causes and consequences of variation in diversity? How is diversity related to temporal variability? stability diversity History of ideas on diversity and stability Wild speculation- Elton 1958 MacArthur 1955

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slide2
What are the causes and consequences of variation in diversity?

How is diversity related to temporal variability?

slide3
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

slide4
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

slide5
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

slide6
stability

stability

stability

diversity

diversity

diversity

History of ideas

  • Wild speculation-
  • Math defies intuition-
  • The role of interaction strength-
how are diversity and stability related in nature
How are diversity and stability related in nature?

What can species-time relations tell us

about diversity and stability?

slide8
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
slide9
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

how do species partition time if diversity is driven by history11
How do species partition time…if diversity is driven by history ?

total richness

time

time

time

Shurin 2007 Oikos 116: 957

how do species partition time if diversity is driven by history12
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

how do species partition time if diversity prevents colonization
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

how do species partition time if diversity facilitates colonization
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

how do species partition time if environmental variability increases diversity
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

slide16
Model predictions:

Correlation with long-term richness

Shurin 2007 Oikos 116: 957

slide17
And the data say…

Toolik

SE AK

ELA

Quebec

Kodiak

Dorsett

Lake Geneva

Washington

Wisconsin

36 lakes

483 lake-years

5,364 samples

slide18
Daily, annual and inter-annual richness

Shurin et al. 2007 Ecology Letters 10: 127

slide19
Richness and turnover

Shurin et al. 2007 Ecology Letters 10: 127

slide20
Richness and turnover

Shurin et al. 2007 Ecology Letters 10: 127

slide21
Richness and turnover

Shurin et al. 2007 Ecology Letters 10: 127

slide22
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
environmental stability and diversity a double edged sword
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?

the data set26
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

the data set27
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

the data set28
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

how do we partition environmental variability among time scales
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
how do we partition environmental variability among time scales30
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

slide33
Interannual =

0.14

Seasonal =

0.008

Residual =

0.02

how does variability relate to zooplankton diversity
How does variability relate to zooplankton diversity?
  • Long-term mean
  • Interannual variability
  • Seasonal variability
  • Residual (unpredictable) variability
zooplankton species richness and residual variability
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
slide46
Interannual and residual variation are better predictors of diversityaverage conditions and seasonality- not so much
conclusions
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
thanks
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
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