Elevated CO2 and N: The Future of PlantPollinator Interactions

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Environmental Change and Pollination Ecology in a
common legume, Trifolium repens
Nicole E. Miller Tiffany M. Knight Washington
University in St. Louis
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Environmental Change

• Anthropogenic activities changing our environment
• Tropospheric Ozone is increasing, particular in
  urban areas
• Agricultural fertilizers are also enhancing
  biologically available P and K
• Salt from road runoff is entering ecosystems
• Climate factors changing as secondary impact
  of environmental change

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Environmental Change

• Atmospheric CO2 Concentrations
• Expected to double over next 100 years (IPCC
  2001)
• Fossil fuel combustion
• Coal
• Gasoline
• Burning of vegetation and trash

4
Environmental Change

• Human beings fix more nitrogen (N) than any other
  source (Vitousek et.al. 1997 IPCC2001)
• Agricultural inputs
• legumes
• Synthetic fertilizers
• Fossil fuel combustion (NOx)

Intergovernmental Panel on Climate Change 2001
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Environmental Change
Environmental Change factor

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Environmental change and Floral Traits
Environmental Change factor
Floral traits
Floral Output

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Environmental change and Floral Traits
Environmental Change factor
Floral traits
Floral Output


Wagner et. al. 2001, Jablonski et al. 2002,
Garbutt and Bazzaz 1984
Wagner et. al. 2001, Erhardt and Rusterholz 1998
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Environmental change and Floral Traits
Environmental Change factor
Floral traits
Floral Output


?()
?(-)
Henning et. al. 1996, Drake et. al. 1997,
Mevi-Schütz et. al. 2003, King et. al. 2004


Paterson et. al. 1997
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Environmental change and Floral Traits
Environmental Change factor
Floral traits
Environmental Change factor
Floral traits
Floral Output



?()
?(-)


Osborne et. al. 1997


Scagel 2004 (mycorrhizal inoculation)
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Environmental change and reproductive success
Environmental Change factor
Floral traits
Reproductive success

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Environmental change and reproductive success
Environmental Change factor
Floral traits
Reproductive success
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Environmental change and reproductive success
Environmental Change factor
Floral traits
Reproductive success


Wagner 2001, Jablonski et. al. 2002 Thürig et.
al. 2003 Quadari and Reid 2005 Tromp et. al.
1994
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Environmental change and reproductive success
Environmental Change factor
Floral traits
Reproductive success


0
0
Germination rate, Huxman et. al. 1998, Wagner et.
al. 2001, Thürig et. al. 2003
Germination rate,
Nimje 1993, Wagner et. al. 2001
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Reproductive success and population growth
Environmental Change factor
Floral traits
Reproductive success
Population growth
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Reproductive success and population growth
Environmental Change factor
Floral traits
Reproductive success
Population growth
?
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Reproductive success and population growth
Environmental Change factor
Floral traits
Reproductive success
Population growth
?

Shimizu et. al. 1998
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Grand Scheme
Floral traits
Reproductive success
Population growth
Environmental Change factor
Floral Output



?

?()
?(-)
?


0
0
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Grand Scheme
Floral traits
Reproductive success
Population growth
Environmental Change factor
Floral Output
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Grand Scheme
Floral traits
Pollination success
Reproductive success
Population growth
Environmental Change factor
Floral Output
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Importance of Pollination

• 90 flowering plants depend
• on pollinators for some degree
• of fertilization
• (Buchman and Nabhan 1996)
• Have direct impact on plant demography and growth
  rate via reproductive success (Ashman 2004)
• Plants shown to compete for pollinators limited
  resource (Campbell 1985)

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Grand Scheme
Floral traits
Reproductive success
Population growth
Environmental Change factor
Pollination success
Floral Output

?


-
?


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Grand Scheme
Floral traits
Pollination success
Reproductive success
Population growth
Environmental Change factor
Floral Output


23
Grand Scheme
Floral traits
Pollination success
Reproductive success
Population growth
Environmental Change factor
Floral Output



-
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Grand Scheme
Floral traits
Pollination success
Reproductive success
Population growth
Environmental Change factor
Floral Output



-


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Grand Scheme
Floral traits
Pollination success
Reproductive success
Population growth
Environmental Change factor
Floral Output



-


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Grand Scheme
Floral traits
Pollination success
Reproductive success
Population growth
Environmental Change factor
Floral Output



-


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Grand Scheme
Floral traits
Pollination success
Reproductive success
Population growth
Environmental Change factor
Floral Output



-


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Methods

• Trifolium repens (white clover)
• Legumous perennial w/ rhizobium
• Self-incompatible
• Generalist pollinated
• Chamber experiment

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Methods

• Floral Measurements
• Days to flower
• Inflorescence width, number per plant
• Flower height, number per inflorescence
• Inflorescence longevity

• Pollinator Observations
• 20 minute visual observations
• Pollinator type
• Visit duration
• Flight pattern
• CN measurements

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Results
C sig N sig CxN sig
C sig N sig CxN sig
C S N S CxN S
S p 0.05 MS 0.1 p 0.05 NS p 0.1
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Results
C S N NS CxN NS
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Results
C S N S CxN S
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Results
C MS N MS CxN MS
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Results
C MS N NS CxN NS
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Conclusions

• Pollinator behavior is altered in response to
  Trifolium repens grown under elevated CO2 but not
  enhanced N
• Hypothesis response of pollinators due to
  increase in floral output and possibly alteration
  of nectar quality
• Potentially influence seed output and
  reproductive success gt plant demography

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Discussion

• Differential response gt pollinator composition
  in an area may shift with environmental change
• Pollinators depend on nectar and pollen
  consumption for dietary needs gt could be
  indirectly influenced by environmental change
  (Mevi-Shütz et. al. 2003)
• Species of concern often pollen limited gt
  interaction with pollinators could be important
  to survival (Rymer et. al. 2005)

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Acknowledgments

• Knight lab
• Chase lab
• Alex Harmon-Threatt
• Carla Fresquez
• Pete Van Zandt
• Danforth Plant Sciences Center greenhouse staff
• National Science Foundation

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