Intraspecific Generational Competition In Garlic Mustard

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Intraspecific Generational Competition In Garlic
Mustard

• Butch Squires, Jeff Conners, Kay Gross and Gary
  Mittelbach
• Kelloggs Biological Station

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                            Primary distribution
of garlic mustard in North America. In Canada, it
occursmainly within the Mixedwood Plains
Ecozone, indicated by the hatched
area.            
Invasive Exotic Plants of Canada Fact Sheet No. 2
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• Obligate biennial of Eurasian origin

• Innocuous weed in native habitat

• Named for garlic scent of crushed young leaves

• Primarily spread anthropogenically

• First noted in new York, 1868

• Presently trans-continental in U.S. (2000, 34
  States, 4 Canadian Provinces)

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Why Is Garlic Mustard a Threat?

• Wide habitat tolerance

• Generalist pollinator, self fertile in absence of
  outcrossing

• Prolific seed production (Avg. 350 / plant,
  estimated max. 7900, up to 62,000/meter squared )

• Establishes seed bank (5 yrs )

• Seed easily acquired and transported

• Devotes more biomass to seed production when
  stressed or in disturbed ground

• Root exudates suspected allelopathic, proven
  anti-mycorhizal

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• Potential competition with and exclusion of
  native spring ephemerals in habitat previously
  considered immune

• Prevention of recruitment of tree seedlings in
  deciduous forest

• Essentially immune to native pathogens and
  predators

• Adapting to new habitats

• Low temperature growth and germination

• Exponential rate of spread ( 2X / yr )

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Concerns

• Is A. petiolata displacing native flora in
  Michigan?

• Are bare patches in otherwise lush forest
  understory the result of allelopathic or
  anti-mycorhizal exudates?

• What can be assessed in one midsummer session?

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Hypothesis
Competitive exclusion occurs between first and
second year Garlic Mustard plants
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Experimental Design

• Sample from quadrats visually selected in
  prominent populations

• Sample from random number selected quadrats along
  transects through habitat

• Compare adult to seedling ratios for negative
  correlation

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Materials

• ½ meter square plastic frame

• Meter stick

• Tape measure

• Note book

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Data Results
Correlation -0.30446
Correlation -0.4226
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Significance

• Negative correlation may be due to factors other
  than shading and seed availability

• These factors may feasibly extend to competing
  native species

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Future Research

• Colonizing behavior from initial appearance must
  be tracked

• Pre-existing native populations need to be
  monitored during invasion for effects on
  individual species

• Seed bank temporal viability needs to be assessed
  on a regional basis

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Thanks to All the Faculty and Staff at KBS