Effects of Simulated Herbivory on Alliaria petiolata

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Effects of Simulated Herbivory on Alliaria
petiolata

• Ashley Paschal, Brian Scott,
• Kyle Burns, and Tyler McPheters

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Background

• Problems with invasive species
• Cause a decline in native populations
• Leads to a loss of biodiversity
• Difficult and expensive to manage

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Garlic mustard invasion

• Eradication might be nearly impossible for
  colonized sites
• Autogamous breeding system, high seed production,
  and rapid growing season (Anderson et al. 1996)
• Successful in outcompeting other plants (Meekins
  and McCarthy 1999)
• High tolerance to environmental variation
  (Meekins and McCarthy 2001)

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How do we get rid of them?

• Non-biological eradication
• Fires, herbicides, floods, and mowing
• Possibly effective, but damaging to surrounding
  environment
• Biological controls
• Host-specific herbivores might be a suitable
  solution (Blossey et al. 2001)

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Deciding on a control

• Simulated herbivory
• Benefit from controlling multiple variables
• Better understanding what types of herbivores are
  effective (Baldwin 1990)
• Rebek and ONeil (2005)
• Simulated herbivory shortens lifespan and
  decreases biomass of garlic mustard

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Our study

• How does simulated herbivory affect garlic
  mustard populations in the DePauw Nature Park?
• Hypothesis Increased herbivory will reduce
  survival, growth, and reproduction of garlic
  mustard
• Indicated by differences in height, above-ground
  biomass, and flower number

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Methods

• Location DePauw Nature Park Creekside Trail.
• Initially labeled 40 plots that contained at
  least three (3) rosettes of garlic mustard
• (Hula-hoop sized plots)
• Labeled one plant in each plot as control, low,
  and high.
• Counted leaves on each plant and then performed
  treatments.

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Methods Treatment

• Standard holepunch
• Half of leaves from the two treatment levels were
  punched
• Low One fourth of leaf area removed.
• High Half of leaf area removed

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Methods

• Measured light intensity using a light meter
• Measured soil moisture levels
• Post-treatment
• Number of flowers, height of plants, and
  above-ground biomass.

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Methods

• Statistical Analysis
• Pearson Correlations
• ANOVA

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Results
F 0.530 P gt 0.05
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F 2.861 P gt 0.05
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F 0.229 P gt 0.05
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Correlation Data
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Significant Correlations

• Initial height was correlated with density, total
  number of leaves, number of flowers, final
  height, and biomass.
• Final height was correlated with number of
  flowers, and biomass.
• Biomass was correlated with number of flowers.
• There was also a correlation between initial
  number of leaves and amount of sunlight.
• Flowering date was not correlated with the
  different treatments. Most plants had flowered
  by March 20, 2006 and the remainder had flowered
  by March 27, 2006.

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Discussion

• Our low herbivory and high herbivory treatments
  showed no significant effects on garlic mustard
  plant height, biomass, or number of flowers
  (pgt0.05)
• No significant ANOVA tests, so plants started off
  comparably and treatments did not detectably
  affect growth or reproduction

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Discussion

• Many obvious correlations between response
  variables and initial variables
• i.e. initial number of leaves and initial height
• Less expected but significant correlation seen
  between plant density and height

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Discussion

• Published results have used different methods
• Rebek and ONeil 2005 Effects of simulated
  herbivory on A. petiolata.
• Study on manual flower shoot damage
• Led to decreased plant size and reproduction.
• Bossdorf et al. 2004 Leaf removal led to
  reduced production of seeds and fruits.
• 75 of leaf removal reduced fitness to 81 of
  that of controls.

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Implications

• Results imply that the level of simulated
  herbivory used was not effective
• Currently there are no herbivores in the Nature
  Park that eat garlic mustard
• If we were to introduce an herbivore, it would
  have to more drastically affect garlic mustard to
  be successful in controlling the garlic mustard
  population

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Implications

• Garlic mustard is currently affecting the native
  species of plants at the DePauw Nature Park, so
  it is important to control garlic mustard
• Control of garlic mustard important also for
  regeneration of forest
• New York Times article (May 2, 2006) says that
  GM disrupts interactions between tree seedlings
  and soil mycorrhizae

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Recommendations

• Other strategies for removal of garlic mustard
• pulls, herbicides, controlled fire
• Small, isolated patches that are more manageable
  should be controlled to prevent spread
• Rim trail patches in contrast to rail trail
  flourishing populations

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Works Cited

• Baldwin, I.T. 1990. Herbivory simulations in
  ecological research. TREE 5 91-93.
• Bossdorf, O., S. Schroder, D. Prati, and H. Auge.
  2004. Palatability and tolerance to simulated
  herbivory in native and introduced populations of
  Alliaria petiolata (Brassicaceae). American
  Journal of Botany 91 (6)856-862.
• Blossey, B., V. Nuzzo, H. Hinz, E. Gerber. 2001.
  Developing biological control of Alliaria
  petiolata (M. Bieb.) Cavara and Grande (garlic
  mustard). Natural Areas Journal 21 357-367.
• Meekins, J.F., and B.C. McCarthy. 1999.
  Competitive ability of Alliaria petiolata (garlic
  mustard, Brassicaceae), an invasive,
  nonindigenous forest herb. International Journal
  of Plant Sciences 160 743-752.
• Meekins, J.F., and B.C. McCarthy. 2001. Effect
  of environmental variation on the invasive
  success of a nonindigenous forest herb.
  Ecological Applications 11 1336-1347.
• Rebek, K.A., and R.J. ONeil. 2005. Impact of
  simulated herbivory on Alliaria petiolata
  survival, growth and reproduction. Biological
  Control 34283-289.