What are the causes and consequences of variation in diversity

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What are the causes and consequences of
variation in diversity?
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What are the causes and consequences of
variation in diversity?
How is diversity related to temporal variability?
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What are the causes and consequences of
diversity for ecosystems?
How is diversity related to temporal
variability?How does functional diversity evolve?
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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
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History of ideas

• Math defies intuition-
• May 1973
• Gardner and Ashby 1970

More species greater chance of including
unstable combinations of strong interactions -gt
extinctions and fluctuations if interaction
strength is uniformly distributed
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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. 1998 Nature
But wait, what does strongly skewed mean? So
wonders Spencer Wood
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Interaction strength in intertidal algae is
normally distributed -Spencer Wood
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More speciose communities have more weak
interactors -Spencer Wood
log kurtosis of interactions
log richness
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History of ideas

• Wild speculation-
• Math defies intuition-
• The role of interaction strength-

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How are diversity and stability related in nature?

• Abiotic variability can either increase or
  decrease coexistence
• Chesson and Huntley 1994 Am Nat 150 519

How are diversity and stability related in
natural communities?
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Questions?

• How is diversity related to community temporal
  stability?
• Model
• How do diversity and stability covary in lake
  zooplankton assemblages?
• Data

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How do we measure stability?Species turnover
a daily richness z turnover ST long-term
richness
ST aTz
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How do species partition timeif diversity is
driven by history ?
Shurin 2007 Oikos 116 957
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How do species partition timeif diversity is
driven by history ?
total richness
time
time
time
Shurin 2007 Oikos 116 957
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How do species partition timeif diversity is
driven by history ?
total richness
time
time
time
turnover
daily richness
total richness
total richness
Shurin 2007 Oikos 116 957
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How do species partition timeif diversity
prevents colonization ?
total richness
time
time
time
turnover
daily richness
total richness
total richness
Shurin 2007 Oikos 116 957
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How do species partition timeif diversity
facilitates colonization ?
total richness
time
time
time
turnover
daily richness
total richness
total richness
Shurin 2007 Oikos 116 957
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How do species partition timeif variability
increases diversity ?
total richness
time
time
time
turnover
daily richness
total richness
total richness
Shurin 2007 Oikos 116 957
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Model predictions
Correlation with long-term richness
Shurin 2007 Oikos 116 957
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And the data say
Toolik
SE AK
ELA
Quebec
Kodiak
Dorsett
Lake Geneva
Washington
Wisconsin
36 lakes 483 lake-years 5,364 samples
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Daily, annual and inter-annual richness
Shurin et al. 2007 Ecology Letters 10 127
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Richness and turnover
Shurin et al. 2007 Ecology Letters 10 127
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Richness and turnover
Shurin et al. 2007 Ecology Letters 10 127
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Richness and turnover
Shurin et al. 2007 Ecology Letters 10 127
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How do temporal components of richness change
with latitude and area?
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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

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How does environmental variability affect
diversity and stability?
pH
Date
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Seasonal environmental variability
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How is diversity related to environmental
variation?

• Mean conditions vs. variability
• Variation on seasonal, annual, and interannual
  time scales

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How does functional diversity evolve?

• A tale of two radiations
• Niche divergence
• sticklebacks
• with Luke Harmon, Blake Matthews, Simone Des
  Roches, and Dolph Schluter
• Sexual selection
• calanoid copepods
• with Blake Matthews and Stephen Hausch

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Divergent effects of benthic and pelagic fish
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Divergent effects of benthic and pelagic fish
Axis 1
Axis 1
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Conclusions from sticklebacks

• Functional diversity can emerge very early in
  adaptive radiation (10,000 years) and can alter
  ecosystem processes
• Effects of different morphs are difficult to
  predict

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Calanoid copepodswith Blake Matthews and Stephen
Hausch
Species are morphologically similar
but are they ecologically equivalent?
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Questions about copepods

• Are species different in morphology, diet and
  ecosystem impacts?
• How does variation among local populations
  compare to differences between species?

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How much inter- and intra-specific morphological
variation?Stephen Hauschs Honors thesis at UBC
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Inter-specific exceeds intra, but differences
between populations are significant Stephen
Hauschs Honors thesis at UBC
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Diaptomus species have different trophic
positions Blake Matthews
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F4,315.8, p 0.001
TL4
5
4
Trophic Position
3
TL3
2
Acanthodiaptomus denticornis
Leptodiaptomus ashlandi
Hesperodiaptomus franciscanus
1
Leptodiaptomus tyrelli
Skistodiaptomus oregonensis
TL2
0
AD
HF
LA
LT
SO
(Nlakes7)
(8)
(7)
(6)
(8)
Diaptomus copepod species
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Do species have different ecological
impacts?with Blake Matthews
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(No Transcript)
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Skistodiaptomus oregonensis (A,B)
Hesperodiaptomus franciscanus (A)
Leptodiaptomus ashlandi (A,B)
A
B
B
B
A
A
A
B
B
B
A
A
A
B
B
B
A
A
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Conclusions

• Calanoid copepods show both inter- and
  intra-specific morphological variability
• interspecific is generally greater
• Species have different diets
• Species and populations have different impacts on
  microbial communities

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What about other supposedly ecologically
neutral radiations?
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Questions?

• How does environmental variation affect
  diversity?
• How does intra-specific diversity shape
  ecosystems?
• How fast does trophic position evolve?