Transcript The Affect of Simulated Herbivory on Alliaria petiolata

Effects of Simulated Herbivory
on Alliaria petiolata
Ashley Paschal, Brian Scott,
Kyle Burns, and Tyler McPheters
Background
• Problems with invasive species
– Cause a decline in native populations
– Leads to a loss of biodiversity
• Difficult and expensive to manage
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)
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)
Deciding on a control
• Simulated herbivory
– Benefit from controlling multiple variables
– Better understanding what types of herbivores
are effective (Baldwin 1990)
• Rebek and O’Neil (2005)
– Simulated herbivory shortens lifespan and
decreases biomass of garlic mustard
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
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.
Methods – Treatment
• Standard hole–punch
• Half of leaves from
the two treatment
levels were punched
• Low – One fourth of
leaf area removed.
• High – Half of leaf
area removed
Methods
• Measured light
intensity using a light
meter
• Measured soil
moisture levels
• Post-treatment:
– Number of flowers,
height of plants, and
above-ground
biomass.
Methods
• Statistical Analysis:
– Pearson Correlations
– ANOVA
Results
Treatment Effect on Final Height
Final Height (cm)
140
120
Control
100
Low Treatment
80
High Treatment
60
40
20
0
F = 0.530
P > 0.05
Treatment Effect on Biomass
10
Biomass (g)
8
Control
6
Low Treatment
High Treatment
4
2
0
F = 2.861
P > 0.05
Treatment Effect on Number of Flowers
Number of Flowers
120
100
Control
80
Low Treatment
60
High Treatment
40
20
0
F = 0.229
P > 0.05
Correlation Data
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.
Discussion
• Our low herbivory and high herbivory treatments
showed no significant effects on garlic mustard
plant height, biomass, or number of flowers
(p>0.05)
• No significant ANOVA tests, so plants started off
comparably and treatments did not detectably
affect growth or reproduction
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
Discussion
• Published results have used different methods
• Rebek and O’Neil 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.
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
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
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
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. O’Neil. 2005. Impact of simulated herbivory on
Alliaria petiolata survival, growth and reproduction. Biological Control
34:283-289.